ZFS on 10-STABLE r281159: programs, accessing ZFS pauses for minutes in state [*kmem arena]

[Lev Serebryakov]

Hello Steven,

Thursday, July 30, 2015, 2:49:21 PM, you wrote:

> You don't need to do that as record set size is a min not a max, if you
> don't force it large files will still be stored efficiently.
  Oh, I thought it is max after reading some blog-posts and forum threads
(this one, for example:
https://forums.freebsd.org/threads/1mb-recordsize-performance-recordsize-discussion.50414/
and this one https://blogs.oracle.com/roch/entry/tuning_zfs_recordsize and
this https://www.joyent.com/blog/bruning-questions-zfs-record-size) Does it mean, that
files could not occupy less than 128K with default setting?

  Anyway, I'll recreate pool.

>>   It looks FreeBSD contains bug about year ago which leads to this behavior,
>> but mailing lists says, that it was fixed in r272221, 10 months ago.
> When this happens what is the state of memory on the machine?
  Now I'm in single-user mode and have some problems to analyze massive
 output of "vmstat -z" :) top shows 4.5-5G of total ARC size and very low
 (~150Mb) free memory.

> Top will give a good overview, while sysctl vm.stats.vm and vmstat -z 
> will provide some detail.

> If you're seeing significant memory pressure, which could well be the 
> case with a mixed ZFS UFS system during this transfer (they use
 Now I have pure ZFS situation, with ZFS to ZFS transfer. Mixed scenario
 with UFS to ZFS transfer didn't show this behavior.

> competing memory resource pools) then you could try limiting ARC via 
> vfs.zfs.arc_max
 I'll try to set it ot 3G...

> You could also see if the patch on 
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594 help.
 I should try this, but for now I should migrate as quickly as possible &
return my spare HDDs which are lent to me for short time...

-- 
Best regards,
 Lev                            mailto:lev at FreeBSD.org