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 <allanj...@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
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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.
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?
Jakob
Could you please retest with the patch below applied, instead of
reverting r338416?
diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
index 2bc065e12509..9b039b7d4a96 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
@@ -538,7 +538,7 @@ typedef struct arc_state {
*/
int zfs_arc_meta_prune = 10000;
unsigned long zfs_arc_dnode_limit_percent = 10;
-int zfs_arc_meta_strategy = ARC_STRATEGY_META_BALANCED;
+int zfs_arc_meta_strategy = ARC_STRATEGY_META_ONLY;
int zfs_arc_meta_adjust_restarts = 4096;
/* The 6 states: */
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