[zfs-discuss] ZFS 0.6.5.3 seems to be using a LOT more processes than before

webman at manfbraun.de webman at manfbraun.de
Mon Dec 21 20:16:42 EST 2015


Hi !

Really interesting numbers ...
Arch, Kernel 4.2.5, pools: ssd:500 GB, mirror:2x3TB
Just nearly unused machine ...

[u at grid ~]# ps aux | grep -i spl | wc -l
70
[u at grid ~]# ps aux | grep -i z_ | wc -l
642

/etc/modprobe.d/spl.conf:
options spl spl_taskq_thread_dynamic=1

Regards,
Manfred


> -----Original Message-----
> From: zfs-discuss [mailto:zfs-discuss-bounces at list.zfsonlinux.org] On Behalf Of
> Dan Swartzendruber via zfs-discuss
> Sent: Monday, December 21, 2015 11:24 PM
> To: zfs-discuss at list.zfsonlinux.org; Alex Braunegg
> Subject: Re: [zfs-discuss] ZFS 0.6.5.3 seems to be using a LOT more processes
> than before
> 
> On 2015-12-21 17:19, Alex Braunegg via zfs-discuss wrote:
> > When looking at the default settings of SPL / ZFS when compared to the
> > man pages, there are quite a number of differences as to what the man
> > pages say should be the default vs what actually is the default.
> > One SPL module parameter that may be related to this issue is:
> >
> > spl_taskq_thread_dynamic (int)
> >
> > Allow dynamic taskqs. When enabled taskqs which set the TASKQ_DYNAMIC
> > flag will by default create only a single thread. New threads will be
> > created on demand up to a maximum allowed number to facilitate the
> > completion of outstanding tasks. Threads which are no longer needed
> > will be promptly destroyed. By default this behavior is enabled but it
> > can be disabled to aid performance analysis or troubleshooting.
> > Default value: 1
> >
> >
> > However, if you compile ZoL from source for 0.6.5.3 from
> > http://archive.zfsonlinux.org/downloads/zfsonlinux/spl/spl-0.6.5.3.tar.gz
> > and
> > http://archive.zfsonlinux.org/downloads/zfsonlinux/zfs/zfs-0.6.5.3.tar.gz
> > or install any package derived from these sources,
> > spl_taskq_thread_dynamic appears to default to 0
> >
> > In my testing, when set to 0, and after a clean reboot, with no system
> > access I get the following:
> >
> > -bash-4.1# ps aufx | grep z_ | wc -l
> > 318
> > -bash-4.1# ps aufx | grep spl | wc -l
> > 70
> >
> > When setting this value to 1 and rebooting, again with no system
> > access:
> >
> > -bash-4.1# ps aufx | grep z_ | wc -l
> > 38
> > -bash-4.1# ps aufx | grep spl | wc -l
> > 4
> >
> >
> > Can you check this value on your systems?
> >
> > 	cat /sys/module/spl/parameters/spl_taskq_thread_dynamic
> >
> 
> I have two hosts, one a backup server running centos7, with zfs from
> package.  I get your first result.  I also have an iscsi server running
> esos, with zfs build from source, and get second result.
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