On Tue, Aug 6, 2019 at 12:48 AM Janek Bevendorff
> However, now my client processes are basically in
constant I/O wait
> state and the CephFS is slow for everybody. After I restarted the copy
> job, I got around 4k reqs/s and then it went down to 100 reqs/s with
> everybody waiting their turn. So yes, it does seem to help, but it
> increases latency by a magnitude.
4k req/s is too fast for a create workload on one MDS. That must
include other operations like getattr.
Addition: I reduced the number to 256K and the cache
inflating instantly (with about 140 reqs/s). So I reset it to 512K and
the cache size started reducing slowly, though with fewer reqs/s.
So I guess it is solving the problem, but only by trading it off against
severe latency issues (order of magnitude as we saw).
I wouldn't expect such extreme latency issues. Please share:
ceph config dump
ceph daemon mds.X cache status
and the two perf dumps one second apart again please.
Also, you said you removed the aggressive recall changes. I assume you
didn't reset them to the defaults, right? Just the first suggested
Patrick Donnelly, Ph.D.
He / Him / His
Senior Software Engineer
Red Hat Sunnyvale, CA