On 9/7/18 6:06 PM, Mark Johnston wrote: > On Fri, Sep 07, 2018 at 03:40:52PM +0200, Jakob Alvermark wrote: >> On 9/6/18 2:28 AM, Mark Johnston wrote: >>> On Wed, Sep 05, 2018 at 11:15:03PM +0300, Subbsd wrote: >>>> On Wed, Sep 5, 2018 at 5:58 PM Allan Jude <allanjude_at_freebsd.org> wrote: >>>>> On 2018-09-05 10:04, Subbsd wrote: >>>>>> Hi, >>>>>> >>>>>> I'm seeing a huge loss in performance ZFS after upgrading FreeBSD 12 >>>>>> to latest revision (r338466 the moment) and related to ARC. >>>>>> >>>>>> I can not say which revision was before except that the newver.sh >>>>>> pointed to ALPHA3. >>>>>> >>>>>> Problems are observed if you try to limit ARC. In my case: >>>>>> >>>>>> vfs.zfs.arc_max="128M" >>>>>> >>>>>> I know that this is very small. However, for two years with this there >>>>>> were no problems. >>>>>> >>>>>> When i send SIGINFO to process which is currently working with ZFS, i >>>>>> see "arc_reclaim_waiters_cv": >>>>>> >>>>>> e.g when i type: >>>>>> >>>>>> /bin/csh >>>>>> >>>>>> I have time (~5 seconds) to press several times 'ctrl+t' before csh is executed: >>>>>> >>>>>> load: 0.70 cmd: csh 5935 [arc_reclaim_waiters_cv] 1.41r 0.00u 0.00s 0% 3512k >>>>>> load: 0.70 cmd: csh 5935 [zio->io_cv] 1.69r 0.00u 0.00s 0% 3512k >>>>>> load: 0.70 cmd: csh 5935 [arc_reclaim_waiters_cv] 1.98r 0.00u 0.01s 0% 3512k >>>>>> load: 0.73 cmd: csh 5935 [arc_reclaim_waiters_cv] 2.19r 0.00u 0.01s 0% 4156k >>>>>> >>>>>> same story with find or any other commans: >>>>>> >>>>>> load: 0.34 cmd: find 5993 [zio->io_cv] 0.99r 0.00u 0.00s 0% 2676k >>>>>> load: 0.34 cmd: find 5993 [arc_reclaim_waiters_cv] 1.13r 0.00u 0.00s 0% 2676k >>>>>> load: 0.34 cmd: find 5993 [arc_reclaim_waiters_cv] 1.25r 0.00u 0.00s 0% 2680k >>>>>> load: 0.34 cmd: find 5993 [arc_reclaim_waiters_cv] 1.38r 0.00u 0.00s 0% 2684k >>>>>> load: 0.34 cmd: find 5993 [arc_reclaim_waiters_cv] 1.51r 0.00u 0.00s 0% 2704k >>>>>> load: 0.34 cmd: find 5993 [arc_reclaim_waiters_cv] 1.64r 0.00u 0.00s 0% 2716k >>>>>> load: 0.34 cmd: find 5993 [arc_reclaim_waiters_cv] 1.78r 0.00u 0.00s 0% 2760k >>>>>> >>>>>> this problem goes away after increasing vfs.zfs.arc_max >>>>>> _______________________________________________ >>>>>> freebsd-current_at_freebsd.org mailing list >>>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-current >>>>>> To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org" >>>>>> >>>>> Previously, ZFS was not actually able to evict enough dnodes to keep >>>>> your arc_max under 128MB, it would have been much higher based on the >>>>> number of open files you had. A recent improvement from upstream ZFS >>>>> (r337653 and r337660) was pulled in that fixed this, so setting an >>>>> arc_max of 128MB is much more effective now, and that is causing the >>>>> side effect of "actually doing what you asked it to do", in this case, >>>>> what you are asking is a bit silly. If you have a working set that is >>>>> greater than 128MB, and you ask ZFS to use less than that, it'll have to >>>>> constantly try to reclaim memory to keep under that very low bar. >>>>> >>>> Thanks for comments. Mark was right when he pointed to r338416 ( >>>> https://svnweb.freebsd.org/base/head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c?r1=338416&r2=338415&pathrev=338416 >>>> ). Commenting aggsum_value returns normal speed regardless of the rest >>>> of the new code from upstream. >>>> I would like to repeat that the speed with these two lines is not just >>>> slow, but _INCREDIBLY_ slow! Probably, this should be written in the >>>> relevant documentation for FreeBSD 12+ >> Hi, >> >> I am experiencing the same slowness when there is a bit of load on the >> system (buildworld for example) which I haven't seen before. > Is it a regression following a recent kernel update? Yes. > >> I have vfs.zfs.arc_max=2G. >> >> Top is reporting >> >> ARC: 607M Total, 140M MFU, 245M MRU, 1060K Anon, 4592K Header, 217M Other >> 105M Compressed, 281M Uncompressed, 2.67:1 Ratio >> >> Should I test the patch? > I would be interested in the results, assuming it is indeed a > regression. This gets more interesting. Kernel + world was at r338465 I was going to test the patch, but since I had updated the src tree to r338499 I built it first without your patch. Now, at r338499, without the patch, it doesn't seem to hit the performance problem. vfs.zfs.arc_max is still set to 2G ARC display in top is around 1000M total, haven't seen go above about 1200M, even if I stress it.Received on Sat Sep 08 2018 - 09:56:10 UTC
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