On 04 Jun 2014, at 16:06, Sage Weil <s...@inktank.com> wrote: > On Wed, 4 Jun 2014, Dan Van Der Ster wrote: >> Hi Sage, all, >> >> On 21 May 2014, at 22:02, Sage Weil <s...@inktank.com> wrote: >> >>> * osd: allow snap trim throttling with simple delay (#6278, Sage Weil) >> >> Do you have some advice about how to use the snap trim throttle? I saw >> osd_snap_trim_sleep, which is still 0 by default. But I didn't manage to >> follow the original ticket, since it started out as a question about >> deep scrub contending with client IOs, but then at some point you >> renamed the ticket to throttling snap trim. What exactly does snap trim >> do in the context of RBD client? And can you suggest a good starting >> point for osd_snap_trim_sleep = ? ? > > This is a coarse hack to make the snap trimming slow down and let client > IO run by simply sleeping between work. I would start with something > smallish (.01 = 10ms) after deleting some snapshots and see what effect it > has on request latency. Unfortunately it's not a very intuitive knob to > adjust, but it is an interim solution until we figure out how to better > prioritize this (and other) background work. >
Thanks Sage. Is this delay applied per object being removed or at some higher granularity? And BTW, I was also curious why you’ve only added a throttle to the snap trim ops. Are object/rbd/pg/pool deletions somehow less disruptive to client IOs? Cheers, Dan > In short, if you do see a performance degradation after removing snaps, > adjust this up or down and see how it changes that. If you don't see a > degradation, then you're lucky and don't need to do anything. :) > > You can adjust this on running OSDs with something like 'ceph daemon > osd.NN config set osd_snap_trim_sleep .01' or with 'ceph tell osd.* > injectargs -- --osd-snap-trim-sleep .01'. > > sage > _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
