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Date:      Mon, 12 Oct 2009 09:56:08 +0200
From:      Attila Nagy <bra@fsn.hu>
To:        Pawel Jakub Dawidek <pjd@FreeBSD.org>
Cc:        freebsd-fs@FreeBSD.org
Subject:   Re: ARC size constantly shrinks, then ZFS slows down extremely
Message-ID:  <4AD2E118.2050202@fsn.hu>
In-Reply-To: <20091008160718.GB2134@garage.freebsd.pl>
References:  <4AC1E540.9070001@fsn.hu> <4AC5B2C7.2000200@fsn.hu> <20091002184526.GA1660@garage.freebsd.pl> <4ACDA5EA.2010600@fsn.hu> <4ACDDED0.2070707@fsn.hu> <20091008160718.GB2134@garage.freebsd.pl>

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Pawel Jakub Dawidek wrote:
> On Thu, Oct 08, 2009 at 02:45:04PM +0200, Attila Nagy wrote:
>   
>> Attila Nagy wrote:
>>     
>>> Hello,
>>>
>>> Pawel Jakub Dawidek wrote:
>>>       
>>>> On Fri, Oct 02, 2009 at 09:59:03AM +0200, Attila Nagy wrote:
>>>>
>>>>         
>>>>> Backing out this change from the 8-STABLE kernel:
>>>>> http://svn.freebsd.org/viewvc/base/head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c?r1=191901&r2=191902 
>>>>>
>>>>>
>>>>> makes it survive about half and hour of IMAP searching. Of course 
>>>>> only time will tell whether this helps in the long run, but so far 
>>>>> 10/10 tries succeeded to kill the machine with this method...
>>>>>    
>>>>>           
>>>> Could you try this patch:
>>>>
>>>>    http://people.freebsd.org/~pjd/patches/arc.c.4.patch
>>>>  
>>>>         
>>> It seems (after running for two days) that this fixes my problem. And 
>>> I see that Kip has came out with a similar version (which I couldn't 
>>> yet test, but hope that will also do).
>>>       
>> It seems that I was a little bit quick regarding this.
>> The machine just stopped with this:
>> last pid: 32358;  load averages:  0.01,  0.04,  0.12    up 2+06:33:56  
>> 14:36:25
>> 114 processes: 1 running, 112 sleeping, 1 zombie
>> CPU:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
>> Mem: 536M Active, 63M Inact, 393M Wired, 8K Cache, 111M Buf
>> Swap: 4096M Total, 15M Used, 4081M Free
>>
>>  PID USERNAME  THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
>> 24025 root        1  44    0  3932K   992K vmwait  0   6:06  0.00% zpool
>> 84190 root        1  44    0  4700K  1592K CPU1    1   4:17  0.00% top
>> 99029 root        1  44    0  4132K  1212K nanslp  1   3:53  0.00% gstat
>> 26317 root        1  44    0  1528K   352K piperd  1   3:38  0.00% 
>> readproctitl
>> 49143    125      4  45    0 12248K  3788K sigwai  0   2:50  0.00% 
>> milter-greyl
>> 39969 root        1  44    0  1536K   516K vmwait  0   2:50  0.00% supervise
>> 40241 root        1  44    0  1536K   516K vmwait  0   2:47  0.00% supervise
>> 44633 root        1  44    0  1536K   512K vmwait  0   2:43  0.00% supervise
>> 43434 root        1  44    0  1536K   516K vmwait  0   2:43  0.00% supervise
>> 50575 root        1  44    0  1536K   516K vmwait  0   2:42  0.00% supervise
>> 45510 root        1  44    0  1536K   512K vmwait  0   2:42  0.00% supervise
>> 58146     60      1  44    0   264M  8828K pfault  0   2:32  0.00% imapd
>> 47526    389      6  44    0 92688K  2296K ucond   1   1:29  0.00% slapd
>> 5417 root        1  44    0  9396K  1680K pfault  1   1:26  0.00% sshd
>> 13147 root        1  44    0  3340K   860K vmwait  1   0:45  0.00% syslogd
>> 92597 root        1  44    0  9396K  1676K pfault  1   0:39  0.00% sshd
>> 26437    125      1  44    0  6924K  1700K vmwait  0   0:33  0.00% qmgr
>>
>> The above top was refreshing, but every other stuff on different ssh 
>> consoles (like a running zpool iostat and gstat) was frozen.
>> Even top stopped when I have resized the window.
>>     
>
> Please try Kip's patch that was committed, it changes priorities a bit,
> which should help.
>   
My i386 machine is still alive after two days of uptime (with your 
patch, it lived for about two days, so I can't say -at least now- that 
it's OK).

The amd64 machine started to loose ARC memory again. See these:
http://people.fsn.hu/~bra/freebsd/20091012-zfs-arcsize/zfs_mem-week.png
http://people.fsn.hu/~bra/freebsd/20091012-zfs-arcsize/memory-week.png

Your patch was active between 7 and 9. You can see that the ARC size was 
somewhat constant.
On october 9, I installed Kip's modification, and ARC size started to 
decrease.
BTW, previously (before october 7) I set the arc min size to 10-15GB 
(can't remember the exact value), but now it runs with the defaults 
(only the max size is set):
vfs.zfs.arc_min: 3623878656
vfs.zfs.arc_max: 28991029248

As you can see, there are plenty of memory. This machine uses UFS as 
well (and writes it heavily), maybe that's what affects ZFS size, by 
caching a lot of stuff?




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