2 Apr
2021
2 Apr
'21
12:31 a.m.
Hi,
With Pacific (16.2.0) out of the door we have the RBD persistent
WriteBack cache for RBD:
https://docs.ceph.com/en/latest/rbd/rbd-persistent-write-back-cache/
Has anybody performed some benchmarks with the RBD cache?
Interested in the QD=1 bs=4k performance mainly.
I don't have any proper hardware available to run benchmarks on yet.
Wido
8 Jun
8 Jun
10:41 p.m.
New subject: RBD persistent writeback cache crash (was: performance)
Hi,
So I've been doing some tests with v16.2.4 with a 2TB Samsung PM983 SSD
mounted under /mnt/rbd-cache
rbd_persistent_cache_mode = ssd
rbd_persistent_cache_size = 2G
rbd_persistent_cache_path = /mnt/rbd-cache
rbd_plugins = pwl_cache
I tried both XFS and EXT4 as the filesystem.
This however leads to fio or 'rbd bench' to crash:
root@infra-138-b16-27:~# fio fio/rbd_rw_1.fio
rbd_w_iodepth_1: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W)
4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
fio-3.1
Starting 1 process
Segmentation fault1)][13.3%][r=0KiB/s,w=14.7MiB/s][r=0,w=3768 IOPS][eta
00m:52s]
root@infra-138-b16-27:~#
(The IOps seem great!)
My fio test is fairly simple:
[global]
ioengine=rbd
clientname=admin
pool=rbd
rbdname=fio1
invalidate=0
bs=4k
runtime=60
direct=1
[rbd_w_iodepth_1]
rw=randwrite
iodepth=1
I have tried to trace it with gdb, but I didn't get further with my
backtrace then:
(gdb) bt
#0 ContextWQ::process (ctx=0x7fffb8081480, this=0x7fffb8012470) at
./src/common/WorkQueue.h:556
#1 ThreadPool::PointerWQ<Context>::_void_process (this=0x7fffb8012470,
item=0x7fffb8081480, handle=...) at ./src/common/WorkQueue.h:341
#2 0x00007fffec600912 in ThreadPool::worker (this=0x7fffb8012018,
wt=<optimized out>) at ./src/common/WorkQueue.cc:117
#3 0x00007fffec601801 in ThreadPool::WorkThread::entry (this=<optimized
out>) at ./src/common/WorkQueue.h:395
#4 0x00007ffff5c796db in start_thread (arg=0x7fffb17fa700) at
pthread_create.c:463
#5 0x00007ffff579e71f in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
Has anybody been able to use pwl_cache successfully?
Wido
On 01/04/2021 21:01, Wido den Hollander wrote:
> Hi,
>
> With Pacific (16.2.0) out of the door we have the RBD persistent
> WriteBack cache for RBD:
> https://docs.ceph.com/en/latest/rbd/rbd-persistent-write-back-cache/
>
> Has anybody performed some benchmarks with the RBD cache?
>
> Interested in the QD=1 bs=4k performance mainly.
>
> I don't have any proper hardware available to run benchmarks on yet.
>
> Wido
> _______________________________________________
> Dev mailing list -- dev(a)ceph.io
> To unsubscribe send an email to dev-leave(a)ceph.io
>
9 Jun
9 Jun
12:34 a.m.
New subject: RBD persistent writeback cache crash (was: performance)
On Tue, Jun 8, 2021 at 7:11 PM Wido den Hollander <wido(a)42on.com> wrote:
Hi,
So I've been doing some tests with v16.2.4 with a 2TB Samsung PM983 SSD
mounted under /mnt/rbd-cache
rbd_persistent_cache_mode = ssd
rbd_persistent_cache_size = 2G
rbd_persistent_cache_path = /mnt/rbd-cache
rbd_plugins = pwl_cache
I tried both XFS and EXT4 as the filesystem.
This however leads to fio or 'rbd bench' to crash:
root@infra-138-b16-27:~# fio fio/rbd_rw_1.fio
rbd_w_iodepth_1: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W)
4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
fio-3.1
Starting 1 process
Segmentation fault1)][13.3%][r=0KiB/s,w=14.7MiB/s][r=0,w=3768 IOPS][eta
00m:52s]
root@infra-138-b16-27:~#
(The IOps seem great!)
My fio test is fairly simple:
[global]
ioengine=rbd
clientname=admin
pool=rbd
rbdname=fio1
invalidate=0
bs=4k
runtime=60
direct=1
[rbd_w_iodepth_1]
rw=randwrite
iodepth=1
I have tried to trace it with gdb, but I didn't get further with my
backtrace then:
(gdb) bt
#0 ContextWQ::process (ctx=0x7fffb8081480, this=0x7fffb8012470) at
./src/common/WorkQueue.h:556
#1 ThreadPool::PointerWQ<Context>::_void_process (this=0x7fffb8012470,
item=0x7fffb8081480, handle=...) at ./src/common/WorkQueue.h:341
#2 0x00007fffec600912 in ThreadPool::worker (this=0x7fffb8012018,
wt=<optimized out>) at ./src/common/WorkQueue.cc:117
#3 0x00007fffec601801 in ThreadPool::WorkThread::entry (this=<optimized
out>) at ./src/common/WorkQueue.h:395
#4 0x00007ffff5c796db in start_thread (arg=0x7fffb17fa700) at
pthread_create.c:463
#5 0x00007ffff579e71f in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
Has anybody been able to use pwl_cache successfully?
Hi Wido,
Unfortunately "rbd_persistent_cache_mode = ssd" cache has shipped
rather broken. This particular crash is most likely already fixed
in master, but there are a few more outstanding. There is a dozen
of "[pwl ssd] ..." tickets in the rbd project, the fixes would be
backported to pacific once the ssd mode is stable enough.
Until then, I would to stick to "rbd_persistent_cache_mode = rwl"
or avoid the pwl_cache plugin entirely.
Thanks,
Ilya
5:15 p.m.
New subject: RBD persistent writeback cache crash (was: performance)
On 08/06/2021 21:04, Ilya Dryomov wrote:
On Tue, Jun 8, 2021 at 7:11 PM Wido den Hollander
<wido(a)42on.com> wrote:
I tried with rwl and am now using XFS with DAX enabled and it works.
Performance-wise I see an improvement of 2x in terms of IOps with qd=1 bs=4k
My kernel is reporting that my PM983 4TB NVMe I am using as a backing
device is 100% util, but that seems off.
Can we expect any fixes for this cache in .5 or .6?
Wido
> Thanks,
>
> Ilya
>
Hi,
So I've been doing some tests with v16.2.4 with a 2TB Samsung PM983 SSD
mounted under /mnt/rbd-cache
rbd_persistent_cache_mode = ssd
rbd_persistent_cache_size = 2G
rbd_persistent_cache_path = /mnt/rbd-cache
rbd_plugins = pwl_cache
I tried both XFS and EXT4 as the filesystem.
This however leads to fio or 'rbd bench' to crash:
root@infra-138-b16-27:~# fio fio/rbd_rw_1.fio
rbd_w_iodepth_1: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W)
4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
fio-3.1
Starting 1 process
Segmentation fault1)][13.3%][r=0KiB/s,w=14.7MiB/s][r=0,w=3768 IOPS][eta
00m:52s]
root@infra-138-b16-27:~#
(The IOps seem great!)
My fio test is fairly simple:
[global]
ioengine=rbd
clientname=admin
pool=rbd
rbdname=fio1
invalidate=0
bs=4k
runtime=60
direct=1
[rbd_w_iodepth_1]
rw=randwrite
iodepth=1
I have tried to trace it with gdb, but I didn't get further with my
backtrace then:
(gdb) bt
#0 ContextWQ::process (ctx=0x7fffb8081480, this=0x7fffb8012470) at
./src/common/WorkQueue.h:556
#1 ThreadPool::PointerWQ<Context>::_void_process (this=0x7fffb8012470,
item=0x7fffb8081480, handle=...) at ./src/common/WorkQueue.h:341
#2 0x00007fffec600912 in ThreadPool::worker (this=0x7fffb8012018,
wt=<optimized out>) at ./src/common/WorkQueue.cc:117
#3 0x00007fffec601801 in ThreadPool::WorkThread::entry (this=<optimized
out>) at ./src/common/WorkQueue.h:395
#4 0x00007ffff5c796db in start_thread (arg=0x7fffb17fa700) at
pthread_create.c:463
#5 0x00007ffff579e71f in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
Has anybody been able to use pwl_cache successfully?
Hi Wido,
Unfortunately "rbd_persistent_cache_mode = ssd" cache has shipped
rather broken. This particular crash is most likely already fixed
in master, but there are a few more outstanding. There is a dozen
of "[pwl ssd] ..." tickets in the rbd project, the fixes would be
backported to pacific once the ssd mode is stable enough.
Until then, I would to stick to "rbd_persistent_cache_mode = rwl"
or avoid the pwl_cache plugin entirely.
5:27 p.m.
New subject: RBD persistent writeback cache crash (was: performance)
On Wed, Jun 9, 2021 at 1:45 PM Wido den Hollander <wido(a)42on.com> wrote:
On 08/06/2021 21:04, Ilya Dryomov wrote:
Some may land in .5 but .6 would probably be the earliest for the ssd
mode to actually be usable.
Thanks,
Ilya
On Tue, Jun 8, 2021 at 7:11 PM Wido den Hollander
<wido(a)42on.com> wrote:
I tried with rwl and am now using XFS with DAX enabled and it works.
Performance-wise I see an improvement of 2x in terms of IOps with qd=1 bs=4k
My kernel is reporting that my PM983 4TB NVMe I am using as a backing
device is 100% util, but that seems off.
Can we expect any fixes for this cache in .5 or .6?
Hi,
So I've been doing some tests with v16.2.4 with a 2TB Samsung PM983 SSD
mounted under /mnt/rbd-cache
rbd_persistent_cache_mode = ssd
rbd_persistent_cache_size = 2G
rbd_persistent_cache_path = /mnt/rbd-cache
rbd_plugins = pwl_cache
I tried both XFS and EXT4 as the filesystem.
This however leads to fio or 'rbd bench' to crash:
root@infra-138-b16-27:~# fio fio/rbd_rw_1.fio
rbd_w_iodepth_1: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W)
4096B-4096B, (T) 4096B-4096B, ioengine=rbd, iodepth=1
fio-3.1
Starting 1 process
Segmentation fault1)][13.3%][r=0KiB/s,w=14.7MiB/s][r=0,w=3768 IOPS][eta
00m:52s]
root@infra-138-b16-27:~#
(The IOps seem great!)
My fio test is fairly simple:
[global]
ioengine=rbd
clientname=admin
pool=rbd
rbdname=fio1
invalidate=0
bs=4k
runtime=60
direct=1
[rbd_w_iodepth_1]
rw=randwrite
iodepth=1
I have tried to trace it with gdb, but I didn't get further with my
backtrace then:
(gdb) bt
#0 ContextWQ::process (ctx=0x7fffb8081480, this=0x7fffb8012470) at
./src/common/WorkQueue.h:556
#1 ThreadPool::PointerWQ<Context>::_void_process (this=0x7fffb8012470,
item=0x7fffb8081480, handle=...) at ./src/common/WorkQueue.h:341
#2 0x00007fffec600912 in ThreadPool::worker (this=0x7fffb8012018,
wt=<optimized out>) at ./src/common/WorkQueue.cc:117
#3 0x00007fffec601801 in ThreadPool::WorkThread::entry (this=<optimized
out>) at ./src/common/WorkQueue.h:395
#4 0x00007ffff5c796db in start_thread (arg=0x7fffb17fa700) at
pthread_create.c:463
#5 0x00007ffff579e71f in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
Has anybody been able to use pwl_cache successfully?
Hi Wido,
Unfortunately "rbd_persistent_cache_mode = ssd" cache has shipped
rather broken. This particular crash is most likely already fixed
in master, but there are a few more outstanding. There is a dozen
of "[pwl ssd] ..." tickets in the rbd project, the fixes would be
backported to pacific once the ssd mode is stable enough.
Until then, I would to stick to "rbd_persistent_cache_mode = rwl"
or avoid the pwl_cache plugin entirely.
1053
days inactive
1122
days old
4 comments
2 participants
participants (2)
-
Ilya Dryomov -
Wido den Hollander