Increasing QD=1 performance (lowering latency)
(Sending it to dev list as people might know it there) Hi, There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph. One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1. Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD. With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3) I benchmark this using fio: $ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. .. 700us latency means the result will be about ~1500 IOps (1000 / 0.7) When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower. My benchmarking / test setup for this: - Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking Things to configure/tune: - C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0) Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well. These are however only very small increments and might help to reduce the latency by another 15% or so. It doesn't bring us anywhere near the 10k IOps other applications can do. And I totally understand that replication over a TCP/IP network takes time and thus increases latency. The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready. In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs? Reaching a ~500us latency would already be great! Thanks, Wido [0]: https://docs.ceph.com/en/latest/dev/crimson/crimson/
Hi Wido No. My results with Ceph (yeah I still use it) are the same, and I use Threadrippers which have almost 4 GHz clockspeed. Network isn't the main problem. The main problem is a lot of program logic written in a complex way which leads to high CPU usage. https://yourcmc.ru/wiki/Ceph_performance if you haven't already seen it. I achieve ~7000 QD=1 iops with Vitastor just because it's much simpler. And I'm gradually progressing feature-wise... :-) Regards, Vitaliy
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
Parallel I/O, by the way, is also awful. I can only reach 36000 write iops in a 14 NVMe cluster with size=2 and 1 OSD per NVMe. This is only ~2500 iops per drive... OK, even if I take 2x * 5x write amplification into account it's ~25000 iops per drive. And drives can push over 300000 iops :-(. Thankfully the performance isn't too critical in this environment. But it's very low :). Regards, Vitaliy
Hi Wido
No. My results with Ceph (yeah I still use it) are the same, and I use Threadrippers which have almost 4 GHz clockspeed.
Network isn't the main problem. The main problem is a lot of program logic written in a complex way which leads to high CPU usage. https://yourcmc.ru/wiki/Ceph_performance if you haven't already seen it.
I achieve ~7000 QD=1 iops with Vitastor just because it's much simpler. And I'm gradually progressing feature-wise... :-)
Regards, Vitaliy
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
_______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
On 05/02/2021 17:24, vitalif@yourcmc.ru wrote:
Hi Wido
No. My results with Ceph (yeah I still use it) are the same, and I use Threadrippers which have almost 4 GHz clockspeed.
Understood.
Network isn't the main problem. The main problem is a lot of program logic written in a complex way which leads to high CPU usage. https://yourcmc.ru/wiki/Ceph_performance if you haven't already seen it.
I'm aware of that Wiki. Network isn't the main issue indeed. Therefor most of the systems I design still run on 10G as anything beyond that doesn't really benefit the cluster in terms of latency.
I achieve ~7000 QD=1 iops with Vitastor just because it's much simpler. And I'm gradually progressing feature-wise... :-)
I'm not looking for something else then Ceph :-) Wido
Regards, Vitaliy
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
Hi Wido, Long time no see! Yeah, this kind of use case is painful for ceph. It really hurts having to send off synchronous replica writes to other OSDs and having to wait to ack the client after *all* have completed. We're only as fast as the slowest replica write for each IO. We can't parallelize thigns at all since it's literally a single client doing a single IO at a time. I don't doubt your ZFS results, it sounds about right given the difference in the IO path. FWIW, I've been doing quite a bit of work lately poking at crimson with the "alienized" bluestore implementation using fio+librbd against a single NVMe backed OSD running on localhost. We're not as fast as the classic OSD for large parallel workloads because we only have a single reactor thread right now. We'll need multiple reactors before we can match classic at high queue depths. At lower queue depths crimson is actually faster though, despite not even using a seastar native objectstore yet. For fun I just did a quick 30s QD1 test on our newer test hardware that Intel donated for the community lab. (Xeon Platinum CPUs, P4510 NVMe drives, etc). This is "almost master" with a couple of additional crimson PRs using a single 16GB pre-allocated RBD volume and all of the system level optimizations you can imagine (no c/p state transitions, ceph-osd pinned to a specific set of cores, fio on localhost, no replication, etc), so it's pretty best case in terms of squeezing out performance. First, here's the classic OSD with bluestore on master: [nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1 Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=14.5MiB/s][w=3723 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2085951: Sun Feb 7 12:55:19 2021 write: IOPS=3804, BW=14.9MiB/s (15.6MB/s)(446MiB/30001msec); 0 zone resets slat (usec): min=2, max=474, avg= 6.85, stdev= 2.73 clat (usec): min=187, max=2658, avg=255.05, stdev=81.21 lat (usec): min=192, max=2704, avg=261.90, stdev=81.75 clat percentiles (usec): | 1.00th=[ 200], 5.00th=[ 204], 10.00th=[ 210], 20.00th=[ 219], | 30.00th=[ 225], 40.00th=[ 231], 50.00th=[ 235], 60.00th=[ 239], | 70.00th=[ 245], 80.00th=[ 253], 90.00th=[ 293], 95.00th=[ 502], | 99.00th=[ 570], 99.50th=[ 611], 99.90th=[ 963], 99.95th=[ 988], | 99.99th=[ 1401] bw ( KiB/s): min=14704, max=16104, per=100.00%, avg=15234.44, stdev=260.42, samples=59 iops : min= 3676, max= 4026, avg=3808.61, stdev=65.10, samples=59 lat (usec) : 250=76.75%, 500=18.23%, 750=4.86%, 1000=0.12% lat (msec) : 2=0.03%, 4=0.01% cpu : usr=3.12%, sys=2.55%, ctx=114166, majf=0, minf=184 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,114148,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=14.9MiB/s (15.6MB/s), 14.9MiB/s-14.9MiB/s (15.6MB/s-15.6MB/s), io=446MiB (468MB), run=30001-30001msec Disk stats (read/write): dm-2: ios=16/103, merge=0/0, ticks=1/24, in_queue=25, util=0.03%, aggrios=31/426, aggrmerge=0/115, aggrticks=4/68, aggrin_queue=76, aggrutil=0.30% sda: ios=31/426, merge=0/115, ticks=4/68, in_queue=76, util=0.30% IMHO this is about as high as we can get right now on classic with everything stacked in our favor. Latency increases quickly once you involve remote network clients, multiple OSDs, and replication, etc. Here's the same test with crimson using alienized bluestore: [nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1 Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=22.0MiB/s][w=5886 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2075392: Sun Feb 7 12:44:32 2021 write: IOPS=5647, BW=22.1MiB/s (23.1MB/s)(662MiB/30001msec); 0 zone resets slat (usec): min=2, max=527, avg= 2.93, stdev= 1.34 clat (usec): min=138, max=41367, avg=173.81, stdev=232.51 lat (usec): min=141, max=41370, avg=176.74, stdev=232.52 clat percentiles (usec): | 1.00th=[ 153], 5.00th=[ 155], 10.00th=[ 155], 20.00th=[ 157], | 30.00th=[ 159], 40.00th=[ 161], 50.00th=[ 163], 60.00th=[ 163], | 70.00th=[ 165], 80.00th=[ 169], 90.00th=[ 176], 95.00th=[ 210], | 99.00th=[ 644], 99.50th=[ 725], 99.90th=[ 832], 99.95th=[ 881], | 99.99th=[ 1221] bw ( KiB/s): min=19024, max=23792, per=100.00%, avg=22632.32, stdev=964.77, samples=59 iops : min= 4756, max= 5948, avg=5658.07, stdev=241.20, samples=59 lat (usec) : 250=97.23%, 500=1.64%, 750=0.77%, 1000=0.33% lat (msec) : 2=0.02%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01% cpu : usr=1.91%, sys=1.78%, ctx=169457, majf=1, minf=336 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,169444,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=22.1MiB/s (23.1MB/s), 22.1MiB/s-22.1MiB/s (23.1MB/s-23.1MB/s), io=662MiB (694MB), run=30001-30001msec Disk stats (read/write): dm-2: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=1/308, aggrmerge=0/11, aggrticks=0/47, aggrin_queue=51, aggrutil=0.27% sda: ios=1/308, merge=0/11, ticks=0/47, in_queue=51, util=0.27% About 50% faster with lower latency, and we haven't even done much to optimize it yet. It's not as fast as your ZFS results below, but at least for a single OSD without replication I'm glad to see crimson is getting us close to being in the same ballpark. I will note that the crimson-osd process was using 23GB (!) in this test so it's still very alpha code (and take the test result with a grain of salt since we're only doing minimal QA right now). At least we have a target to maintain and hopefully improve though as we continue to work toward stabilizing it. Mark On 2/5/21 7:51 AM, Wido den Hollander wrote:
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson/ _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
On 2/7/21 2:43 PM, Mark Nelson wrote:
Hi Wido,
Long time no see! Yeah, this kind of use case is painful for ceph. It really hurts having to send off synchronous replica writes to other OSDs and having to wait to ack the client after *all* have completed. We're only as fast as the slowest replica write for each IO. We can't parallelize thigns at all since it's literally a single client doing a single IO at a time. I don't doubt your ZFS results, it sounds about right given the difference in the IO path. FWIW, I've been doing quite a bit of work lately poking at crimson with the "alienized" bluestore implementation using fio+librbd against a single NVMe backed OSD running on localhost. We're not as fast as the classic OSD for large parallel workloads because we only have a single reactor thread right now. We'll need multiple reactors before we can match classic at high queue depths. At lower queue depths crimson is actually faster though, despite not even using a seastar native objectstore yet.
So the conclusion here kind of is that right now the ~1600 IOps I'm seeing with size=3 over a 10GbE Ethernet netwerk is about the best you can get at the moment Things that might improve it a bit: - 25GbE (slightly lower latency) - Higher clocked CPUs for the OSDs That might bring me to ~1800 IOps, but that's about it, right?
For fun I just did a quick 30s QD1 test on our newer test hardware that Intel donated for the community lab. (Xeon Platinum CPUs, P4510 NVMe drives, etc). This is "almost master" with a couple of additional crimson PRs using a single 16GB pre-allocated RBD volume and all of the system level optimizations you can imagine (no c/p state transitions, ceph-osd pinned to a specific set of cores, fio on localhost, no replication, etc), so it's pretty best case in terms of squeezing out performance. First, here's the classic OSD with bluestore on master:
[nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=14.5MiB/s][w=3723 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2085951: Sun Feb 7 12:55:19 2021 write: IOPS=3804, BW=14.9MiB/s (15.6MB/s)(446MiB/30001msec); 0 zone resets slat (usec): min=2, max=474, avg= 6.85, stdev= 2.73 clat (usec): min=187, max=2658, avg=255.05, stdev=81.21 lat (usec): min=192, max=2704, avg=261.90, stdev=81.75 clat percentiles (usec): | 1.00th=[ 200], 5.00th=[ 204], 10.00th=[ 210], 20.00th=[ 219], | 30.00th=[ 225], 40.00th=[ 231], 50.00th=[ 235], 60.00th=[ 239], | 70.00th=[ 245], 80.00th=[ 253], 90.00th=[ 293], 95.00th=[ 502], | 99.00th=[ 570], 99.50th=[ 611], 99.90th=[ 963], 99.95th=[ 988], | 99.99th=[ 1401] bw ( KiB/s): min=14704, max=16104, per=100.00%, avg=15234.44, stdev=260.42, samples=59 iops : min= 3676, max= 4026, avg=3808.61, stdev=65.10, samples=59 lat (usec) : 250=76.75%, 500=18.23%, 750=4.86%, 1000=0.12% lat (msec) : 2=0.03%, 4=0.01% cpu : usr=3.12%, sys=2.55%, ctx=114166, majf=0, minf=184 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,114148,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=14.9MiB/s (15.6MB/s), 14.9MiB/s-14.9MiB/s (15.6MB/s-15.6MB/s), io=446MiB (468MB), run=30001-30001msec
Disk stats (read/write): dm-2: ios=16/103, merge=0/0, ticks=1/24, in_queue=25, util=0.03%, aggrios=31/426, aggrmerge=0/115, aggrticks=4/68, aggrin_queue=76, aggrutil=0.30% sda: ios=31/426, merge=0/115, ticks=4/68, in_queue=76, util=0.30%
IMHO this is about as high as we can get right now on classic with everything stacked in our favor. Latency increases quickly once you involve remote network clients, multiple OSDs, and replication, etc. Here's the same test with crimson using alienized bluestore:
[nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=22.0MiB/s][w=5886 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2075392: Sun Feb 7 12:44:32 2021 write: IOPS=5647, BW=22.1MiB/s (23.1MB/s)(662MiB/30001msec); 0 zone resets slat (usec): min=2, max=527, avg= 2.93, stdev= 1.34 clat (usec): min=138, max=41367, avg=173.81, stdev=232.51 lat (usec): min=141, max=41370, avg=176.74, stdev=232.52 clat percentiles (usec): | 1.00th=[ 153], 5.00th=[ 155], 10.00th=[ 155], 20.00th=[ 157], | 30.00th=[ 159], 40.00th=[ 161], 50.00th=[ 163], 60.00th=[ 163], | 70.00th=[ 165], 80.00th=[ 169], 90.00th=[ 176], 95.00th=[ 210], | 99.00th=[ 644], 99.50th=[ 725], 99.90th=[ 832], 99.95th=[ 881], | 99.99th=[ 1221] bw ( KiB/s): min=19024, max=23792, per=100.00%, avg=22632.32, stdev=964.77, samples=59 iops : min= 4756, max= 5948, avg=5658.07, stdev=241.20, samples=59 lat (usec) : 250=97.23%, 500=1.64%, 750=0.77%, 1000=0.33% lat (msec) : 2=0.02%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01% cpu : usr=1.91%, sys=1.78%, ctx=169457, majf=1, minf=336 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,169444,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=22.1MiB/s (23.1MB/s), 22.1MiB/s-22.1MiB/s (23.1MB/s-23.1MB/s), io=662MiB (694MB), run=30001-30001msec
Disk stats (read/write): dm-2: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=1/308, aggrmerge=0/11, aggrticks=0/47, aggrin_queue=51, aggrutil=0.27% sda: ios=1/308, merge=0/11, ticks=0/47, in_queue=51, util=0.27%
About 50% faster with lower latency, and we haven't even done much to optimize it yet. It's not as fast as your ZFS results below, but at least for a single OSD without replication I'm glad to see crimson is getting us close to being in the same ballpark. I will note that the crimson-osd process was using 23GB (!) in this test so it's still very alpha code (and take the test result with a grain of salt since we're only doing minimal QA right now). At least we have a target to maintain and hopefully improve though as we continue to work toward stabilizing it.
Crimson is still pretty far away and thus not something which can be used today. Really good to see this though! QD=1 is still very important for many applications but also from a users perspective on how they experience Ceph. Wido
Mark
On 2/5/21 7:51 AM, Wido den Hollander wrote:
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson/ _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
_______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
On 07/02/2021 15:43, Mark Nelson wrote:
Hi Wido,
Long time no see! Yeah, this kind of use case is painful for ceph. It really hurts having to send off synchronous replica writes to other OSDs and having to wait to ack the client after *all* have completed. We're only as fast as the slowest replica write for each IO. We can't parallelize thigns at all since it's literally a single client doing a single IO at a time. I don't doubt your ZFS results, it sounds about right given the difference in the IO path. FWIW, I've been doing quite a bit of work lately poking at crimson with the "alienized" bluestore implementation using fio+librbd against a single NVMe backed OSD running on localhost. We're not as fast as the classic OSD for large parallel workloads because we only have a single reactor thread right now. We'll need multiple reactors before we can match classic at high queue depths. At lower queue depths crimson is actually faster though, despite not even using a seastar native objectstore yet.
For fun I just did a quick 30s QD1 test on our newer test hardware that Intel donated for the community lab. (Xeon Platinum CPUs, P4510 NVMe drives, etc). This is "almost master" with a couple of additional crimson PRs using a single 16GB pre-allocated RBD volume and all of the system level optimizations you can imagine (no c/p state transitions, ceph-osd pinned to a specific set of cores, fio on localhost, no replication, etc), so it's pretty best case in terms of squeezing out performance. First, here's the classic OSD with bluestore on master:
[nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=14.5MiB/s][w=3723 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2085951: Sun Feb 7 12:55:19 2021 write: IOPS=3804, BW=14.9MiB/s (15.6MB/s)(446MiB/30001msec); 0 zone resets slat (usec): min=2, max=474, avg= 6.85, stdev= 2.73 clat (usec): min=187, max=2658, avg=255.05, stdev=81.21 lat (usec): min=192, max=2704, avg=261.90, stdev=81.75 clat percentiles (usec): | 1.00th=[ 200], 5.00th=[ 204], 10.00th=[ 210], 20.00th=[ 219], | 30.00th=[ 225], 40.00th=[ 231], 50.00th=[ 235], 60.00th=[ 239], | 70.00th=[ 245], 80.00th=[ 253], 90.00th=[ 293], 95.00th=[ 502], | 99.00th=[ 570], 99.50th=[ 611], 99.90th=[ 963], 99.95th=[ 988], | 99.99th=[ 1401] bw ( KiB/s): min=14704, max=16104, per=100.00%, avg=15234.44, stdev=260.42, samples=59 iops : min= 3676, max= 4026, avg=3808.61, stdev=65.10, samples=59 lat (usec) : 250=76.75%, 500=18.23%, 750=4.86%, 1000=0.12% lat (msec) : 2=0.03%, 4=0.01% cpu : usr=3.12%, sys=2.55%, ctx=114166, majf=0, minf=184 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,114148,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=14.9MiB/s (15.6MB/s), 14.9MiB/s-14.9MiB/s (15.6MB/s-15.6MB/s), io=446MiB (468MB), run=30001-30001msec
Disk stats (read/write): dm-2: ios=16/103, merge=0/0, ticks=1/24, in_queue=25, util=0.03%, aggrios=31/426, aggrmerge=0/115, aggrticks=4/68, aggrin_queue=76, aggrutil=0.30% sda: ios=31/426, merge=0/115, ticks=4/68, in_queue=76, util=0.30%
IMHO this is about as high as we can get right now on classic with everything stacked in our favor. Latency increases quickly once you involve remote network clients, multiple OSDs, and replication, etc. Here's the same test with crimson using alienized bluestore:
[nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=22.0MiB/s][w=5886 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2075392: Sun Feb 7 12:44:32 2021 write: IOPS=5647, BW=22.1MiB/s (23.1MB/s)(662MiB/30001msec); 0 zone resets slat (usec): min=2, max=527, avg= 2.93, stdev= 1.34 clat (usec): min=138, max=41367, avg=173.81, stdev=232.51 lat (usec): min=141, max=41370, avg=176.74, stdev=232.52 clat percentiles (usec): | 1.00th=[ 153], 5.00th=[ 155], 10.00th=[ 155], 20.00th=[ 157], | 30.00th=[ 159], 40.00th=[ 161], 50.00th=[ 163], 60.00th=[ 163], | 70.00th=[ 165], 80.00th=[ 169], 90.00th=[ 176], 95.00th=[ 210], | 99.00th=[ 644], 99.50th=[ 725], 99.90th=[ 832], 99.95th=[ 881], | 99.99th=[ 1221] bw ( KiB/s): min=19024, max=23792, per=100.00%, avg=22632.32, stdev=964.77, samples=59 iops : min= 4756, max= 5948, avg=5658.07, stdev=241.20, samples=59 lat (usec) : 250=97.23%, 500=1.64%, 750=0.77%, 1000=0.33% lat (msec) : 2=0.02%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01% cpu : usr=1.91%, sys=1.78%, ctx=169457, majf=1, minf=336 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,169444,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=22.1MiB/s (23.1MB/s), 22.1MiB/s-22.1MiB/s (23.1MB/s-23.1MB/s), io=662MiB (694MB), run=30001-30001msec
Disk stats (read/write): dm-2: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=1/308, aggrmerge=0/11, aggrticks=0/47, aggrin_queue=51, aggrutil=0.27% sda: ios=1/308, merge=0/11, ticks=0/47, in_queue=51, util=0.27%
About 50% faster with lower latency, and we haven't even done much to optimize it yet. It's not as fast as your ZFS results below, but at least for a single OSD without replication I'm glad to see crimson is getting us close to being in the same ballpark. I will note that the crimson-osd process was using 23GB (!) in this test so it's still very alpha code (and take the test result with a grain of salt since we're only doing minimal QA right now). At least we have a target to maintain and hopefully improve though as we continue to work toward stabilizing it.
Mark
On 2/5/21 7:51 AM, Wido den Hollander wrote:
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson/ _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
_______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
Hi Mark/Wido Yes this is definitely an important use case, getting high performance without having a very large number of parallel clients/ops (as compared to the number of OSDs). I am happy to hear progress on Crimson, can't wait to see this maturing. One thing you mention on adding more threads to Crimson in the future to match classic at high queue depths, this sounds great but just in case this will lead to locks being added that may impact single queue depth case, even if slightly, i would recommend to maybe have an OSD config value to enable a single thread mode only to give (/in case it gives) the best performance for single queue depth. I run some 1 QD tests on a test Octopus/Bluestore system using 1 OSD ram disk, only 1 replica, clients on localhost, gives approx 0.28 ms latency: rbd bench --io-type write rbd/image-01 --io-threads=1 --io-size 4K --io-pattern rand --rbd_cache=false SEC OPS OPS/SEC BYTES/SEC 1 3584 3599.33 14 MiB/s 2 7241 3628.19 14 MiB/s 3 10833 3616.09 14 MiB/s fio -ioengine=rbd --name=xx --pool=rbd --rbdname=image-01 --iodepth=1 --rw=randwrite --bs=4k --direct=1 --runtime=10 --time_based Run status group 0 (all jobs): WRITE: bw=12.8MiB/s (13.5MB/s), 12.8MiB/s-12.8MiB/s (13.5MB/s-13.5MB/s), io=128MiB (135MB), run=10001-10001msec I think ceph msgr contributes a large part of the latency ceph_perf_msgr_server 127.0.0.1:9000 <http://127.0.0.1:9000>64 10 ceph_perf_msgr_client 127.0.0.1:9000 <http://127.0.0.1:9000>1 1 1000 10 4096 103154 us (count = 1000) -> 103 us (count = 1) this 0.1 ms latency is quite a large overhead for a simple msgr echo test, specially when compared to the latency tests below: tcp client server socket echo test with EPOLL wait (same used in msgr wait events) , 4k block size https://github.com/onestraw/epoll-example Sent 1000000 messages, avg latency 7.117855 us tcp latency qperf 127.0.0.1 tcp_lat latency = 6.04 us ping latency/rtt ping -c1 -q -W1 127.0.0.1 rtt min/avg/max/mdev = 0.018/0.018/0.018/0.000 ms /Maged
On 09/02/2021 20:47, Maged Mokhtar wrote:
On 07/02/2021 15:43, Mark Nelson wrote:
Hi Wido,
Long time no see! Yeah, this kind of use case is painful for ceph. It really hurts having to send off synchronous replica writes to other OSDs and having to wait to ack the client after *all* have completed. We're only as fast as the slowest replica write for each IO. We can't parallelize thigns at all since it's literally a single client doing a single IO at a time. I don't doubt your ZFS results, it sounds about right given the difference in the IO path. FWIW, I've been doing quite a bit of work lately poking at crimson with the "alienized" bluestore implementation using fio+librbd against a single NVMe backed OSD running on localhost. We're not as fast as the classic OSD for large parallel workloads because we only have a single reactor thread right now. We'll need multiple reactors before we can match classic at high queue depths. At lower queue depths crimson is actually faster though, despite not even using a seastar native objectstore yet.
For fun I just did a quick 30s QD1 test on our newer test hardware that Intel donated for the community lab. (Xeon Platinum CPUs, P4510 NVMe drives, etc). This is "almost master" with a couple of additional crimson PRs using a single 16GB pre-allocated RBD volume and all of the system level optimizations you can imagine (no c/p state transitions, ceph-osd pinned to a specific set of cores, fio on localhost, no replication, etc), so it's pretty best case in terms of squeezing out performance. First, here's the classic OSD with bluestore on master:
[nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=14.5MiB/s][w=3723 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2085951: Sun Feb 7 12:55:19 2021 write: IOPS=3804, BW=14.9MiB/s (15.6MB/s)(446MiB/30001msec); 0 zone resets slat (usec): min=2, max=474, avg= 6.85, stdev= 2.73 clat (usec): min=187, max=2658, avg=255.05, stdev=81.21 lat (usec): min=192, max=2704, avg=261.90, stdev=81.75 clat percentiles (usec): | 1.00th=[ 200], 5.00th=[ 204], 10.00th=[ 210], 20.00th=[ 219], | 30.00th=[ 225], 40.00th=[ 231], 50.00th=[ 235], 60.00th=[ 239], | 70.00th=[ 245], 80.00th=[ 253], 90.00th=[ 293], 95.00th=[ 502], | 99.00th=[ 570], 99.50th=[ 611], 99.90th=[ 963], 99.95th=[ 988], | 99.99th=[ 1401] bw ( KiB/s): min=14704, max=16104, per=100.00%, avg=15234.44, stdev=260.42, samples=59 iops : min= 3676, max= 4026, avg=3808.61, stdev=65.10, samples=59 lat (usec) : 250=76.75%, 500=18.23%, 750=4.86%, 1000=0.12% lat (msec) : 2=0.03%, 4=0.01% cpu : usr=3.12%, sys=2.55%, ctx=114166, majf=0, minf=184 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,114148,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=14.9MiB/s (15.6MB/s), 14.9MiB/s-14.9MiB/s (15.6MB/s-15.6MB/s), io=446MiB (468MB), run=30001-30001msec
Disk stats (read/write): dm-2: ios=16/103, merge=0/0, ticks=1/24, in_queue=25, util=0.03%, aggrios=31/426, aggrmerge=0/115, aggrticks=4/68, aggrin_queue=76, aggrutil=0.30% sda: ios=31/426, merge=0/115, ticks=4/68, in_queue=76, util=0.30%
IMHO this is about as high as we can get right now on classic with everything stacked in our favor. Latency increases quickly once you involve remote network clients, multiple OSDs, and replication, etc. Here's the same test with crimson using alienized bluestore:
[nhm@o01 initial]$ sudo /home/nhm/src/fio/fio --ioengine=rbd --direct=1 --bs=4096B --iodepth=1 --end_fsync=1 --rw=randwrite --norandommap --size=16384M --numjobs=1 --runtime=30 --time_based --clientname=admin --pool=cbt-librbd --rbdname=`hostname -f`-0 --invalidate=0 --name=cbt-librbd/`hostname -f`-0-0 cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=22.0MiB/s][w=5886 IOPS][eta 00m:00s] cbt-librbd/o01.vlan104.sepia.ceph.com-0-0: (groupid=0, jobs=1): err= 0: pid=2075392: Sun Feb 7 12:44:32 2021 write: IOPS=5647, BW=22.1MiB/s (23.1MB/s)(662MiB/30001msec); 0 zone resets slat (usec): min=2, max=527, avg= 2.93, stdev= 1.34 clat (usec): min=138, max=41367, avg=173.81, stdev=232.51 lat (usec): min=141, max=41370, avg=176.74, stdev=232.52 clat percentiles (usec): | 1.00th=[ 153], 5.00th=[ 155], 10.00th=[ 155], 20.00th=[ 157], | 30.00th=[ 159], 40.00th=[ 161], 50.00th=[ 163], 60.00th=[ 163], | 70.00th=[ 165], 80.00th=[ 169], 90.00th=[ 176], 95.00th=[ 210], | 99.00th=[ 644], 99.50th=[ 725], 99.90th=[ 832], 99.95th=[ 881], | 99.99th=[ 1221] bw ( KiB/s): min=19024, max=23792, per=100.00%, avg=22632.32, stdev=964.77, samples=59 iops : min= 4756, max= 5948, avg=5658.07, stdev=241.20, samples=59 lat (usec) : 250=97.23%, 500=1.64%, 750=0.77%, 1000=0.33% lat (msec) : 2=0.02%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01% cpu : usr=1.91%, sys=1.78%, ctx=169457, majf=1, minf=336 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%,
=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, =64=0.0% issued rwts: total=0,169444,0,0 short=0,0,0,0 dropped=0,0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs): WRITE: bw=22.1MiB/s (23.1MB/s), 22.1MiB/s-22.1MiB/s (23.1MB/s-23.1MB/s), io=662MiB (694MB), run=30001-30001msec
Disk stats (read/write): dm-2: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=1/308, aggrmerge=0/11, aggrticks=0/47, aggrin_queue=51, aggrutil=0.27% sda: ios=1/308, merge=0/11, ticks=0/47, in_queue=51, util=0.27%
About 50% faster with lower latency, and we haven't even done much to optimize it yet. It's not as fast as your ZFS results below, but at least for a single OSD without replication I'm glad to see crimson is getting us close to being in the same ballpark. I will note that the crimson-osd process was using 23GB (!) in this test so it's still very alpha code (and take the test result with a grain of salt since we're only doing minimal QA right now). At least we have a target to maintain and hopefully improve though as we continue to work toward stabilizing it.
Mark
On 2/5/21 7:51 AM, Wido den Hollander wrote:
(Sending it to dev list as people might know it there)
Hi,
There are many talks and presentations out there about Ceph's performance. Ceph is great when it comes to parallel I/O, large queue depths and many applications sending I/O towards Ceph.
One thing where Ceph isn't the fastest are 4k blocks written at Queue Depth 1.
Some applications benefit very much from high performance/low latency I/O at qd=1, for example Single Threaded applications which are writing small files inside a VM running on RBD.
With some tuning you can get to a ~700us latency for a 4k write with qd=1 (Replication, size=3)
I benchmark this using fio:
$ fio --ioengine=librbd --bs=4k --iodepth=1 --direct=1 .. .. .. ..
700us latency means the result will be about ~1500 IOps (1000 / 0.7)
When comparing this to let's say a BSD machine running ZFS that's on the low side. With ZFS+NVMe you'll be able to reach about somewhere between 7.000 and 10.000 IOps, the latency is simply much lower.
My benchmarking / test setup for this:
- Ceph Nautilus/Octopus (doesn't make a big difference) - 3x SuperMicro 1U with: - AMD Epyc 7302P 16-core CPU - 128GB DDR4 - 10x Samsung PM983 3,84TB - 10Gbit Base-T networking
Things to configure/tune:
- C-State pinning to 1 - CPU governer to performance - Turn off all logging in Ceph (debug_osd, debug_ms, debug_bluestore=0)
Higher clock speeds (New AMD Epyc coming in March!) help to reduce the latency and going towards 25Gbit/100Gbit might help as well.
These are however only very small increments and might help to reduce the latency by another 15% or so.
It doesn't bring us anywhere near the 10k IOps other applications can do.
And I totally understand that replication over a TCP/IP network takes time and thus increases latency.
The Crimson project [0] is aiming to lower the latency with many things like DPDK and SPDK, but this is far from finished and production ready.
In the meantime, am I overseeing some things here? Can we reduce the latency further of the current OSDs?
Reaching a ~500us latency would already be great!
Thanks,
Wido
[0]: https://docs.ceph.com/en/latest/dev/crimson/crimson/ _______________________________________________ Dev mailing list -- dev@ceph.io To unsubscribe send an email to dev-leave@ceph.io
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Hi Mark/Wido
Yes this is definitely an important use case, getting high performance without having a very large number of parallel clients/ops (as compared to the number of OSDs). I am happy to hear progress on Crimson, can't wait to see this maturing. One thing you mention on adding more threads to Crimson in the future to match classic at high queue depths, this sounds great but just in case this will lead to locks being added that may impact single queue depth case, even if slightly, i would recommend to maybe have an OSD config value to enable a single thread mode only to give (/in case it gives) the best performance for single queue depth.
Indeed. High queue depths are great to benchmark with and show millions of IOps. In many cases you also have high QDs, but in real life you also have applications which simply benefit from a lower latency. QD=1
I run some 1 QD tests on a test Octopus/Bluestore system using 1 OSD ram disk, only 1 replica, clients on localhost, gives approx 0.28 ms latency:
rbd bench --io-type write rbd/image-01 --io-threads=1 --io-size 4K --io-pattern rand --rbd_cache=false
SEC OPS OPS/SEC BYTES/SEC 1 3584 3599.33 14 MiB/s 2 7241 3628.19 14 MiB/s 3 10833 3616.09 14 MiB/s
fio -ioengine=rbd --name=xx --pool=rbd --rbdname=image-01 --iodepth=1 --rw=randwrite --bs=4k --direct=1 --runtime=10 --time_based
Run status group 0 (all jobs): WRITE: bw=12.8MiB/s (13.5MB/s), 12.8MiB/s-12.8MiB/s (13.5MB/s-13.5MB/s), io=128MiB (135MB), run=10001-10001msec
I think ceph msgr contributes a large part of the latency
ceph_perf_msgr_server 127.0.0.1:9000 <http://127.0.0.1:9000>64 10 ceph_perf_msgr_client 127.0.0.1:9000 <http://127.0.0.1:9000>1 1 1000 10 4096 103154 us (count = 1000) -> 103 us (count = 1)
this 0.1 ms latency is quite a large overhead for a simple msgr echo test, specially when compared to the latency tests below:
tcp client server socket echo test with EPOLL wait (same used in msgr wait events) , 4k block size https://github.com/onestraw/epoll-example <https://github.com/onestraw/epoll-example> Sent 1000000 messages, avg latency 7.117855 us
tcp latency qperf 127.0.0.1 tcp_lat latency = 6.04 us
With qperf I have 19us latency over a routed 25GbE network. So yes, the msgr overhead of 0.1ms for msgr traffic is pretty high. Wido
ping latency/rtt ping -c1 -q -W1 127.0.0.1 rtt min/avg/max/mdev = 0.018/0.018/0.018/0.000 ms
/Maged
participants (4)
-
Maged Mokhtar
-
Mark Nelson
-
vitalif＠yourcmc.ru
-
Wido den Hollander