[Ocfs2-users] High on buffers and deep on swap
Sunil Mushran
Sunil.Mushran at oracle.com
Mon Apr 9 19:05:13 PDT 2007
Not sure whether I would call that high. It is a 5G box afterall.
It is always hard to figure out memory related issues based on one output.
Call Oracle support. They will give you an oswatcher script that
monitors various stats giving us a much better view into the running
system.
Alexei_Roudnev wrote:
> Suni, you do know it much better - is not is strange a little? (so
> many ext3 inode chache objects, togetrher with 3 GB of cached disk space).
> But I dont see anything wrong below - big 'cached' memory means only
> 'you have so many unused memory that system cached files in it' and
> nothing more. Cached memory is in reality _free for immediate use_
> memory (can be used by anyone immediately).
> What ysstem is doing is _instead of freeing memory and filling it by
> zerous, free unused memory and fill it in by buffer cache data, so
> that if someone need these data he have them at once. If someone need
> more memory, system reuse any of 'chached' memory without any delay
> (because these are buffers which are already written to the disk or
> which was never udpated).
> Big 'cached' value means only _big free memory_.
>
> ----- O riginal Message -----
> *From:* Luis Freitas <mailto:lfreitas34 at yahoo.com>
> *To:* Alexei_Roudnev <mailto:Alexei_Roudnev at exigengroup.com> ;
> Brian Sieler <mailto:blsieler at gmail.com> ;
> ocfs2-users at oss.oracle.com <mailto:ocfs2-users at oss.oracle.com>
> *Sent:* Monday, April 09, 2007 4:32 PM
> *Subject:* Re: [Ocfs2-users] High on buffers and deep on swap
>
> Alexei,
> How can I relate the information on slabtop to the actual memory
> used by buffers?
> I see this on slabtop:
> Active / Total Objects (% used) : 603822 / 649643 (92.9%)
> Active / Total Slabs (% used) : 47216 / 47216 (100.0%)
> Active / Total Caches (% used) : 97 / 133 (72.9%)
> Active / Total Size (% used) : 176601.08K / 181508.49K (97.3%)
> Minimum / Average / Maximum Object : 0.01K / 0.28K / 128.00K
> OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
> 202461 202451 99% 0.54K 28923 7 115692K ext3_inode_cache
> 232206 232153 99% 0.15K 8931 26 35724K dentry_cache
> 29974 26092 87% 0.27K 2141 14 8564K radix_tree_node
> 68250 62400 91% 0.05K 910 75 3640K buffer_head
> 855 855 100% 4.00K 855 1 3420K pmd
> 647 647 100% 4.00K 647 1 2588K size-4096
> 8595 7694 89% 0.25K 573 15 2292K filp
> 20835 17331 83% 0.09K 463 45 1852K vm_area_struct
> 780 767 98% 2.00K 390 2 1560K size-2048
> 18849 7962 42% 0.06K 309 61 1236K size-64
> 2440 632 25% 0.50K 305 8 1220K size-512
> 2926 2889 98% 0.34K 266 11 1064K inode_cache
> 256 256 100% 3.00K 128 2 1024K biovec-(256)
> 600 592 98% 1.38K 120 5 960K task_struct
> 515 512 99% 1.38K 103 5 824K pirpIo
> 5084 2365 46% 0.12K 164 31 656K size-128
> The largest area is about 100Mb, but on free there are over 3Gb on
> the "cached" column:
> [oracle at br001sv0431 ~]$ free
> total used free shared buffers cached
> Mem: 5190736 4461420 729316 0 141836 3265464
> -/+ buffers/cache: 1054120 4136616
> Swap: 2048248 0 2048248
> [oracle at br001sv0431 ~]$
> Regards,
> Luis
>
>
> */Alexei_Roudnev <Alexei_Roudnev at exigengroup.com>/* wrote:
>
> Did you run slabtop ? It can show unreleased buffers in the
> system.
>
> ----- Original Message -----
> *From:* Luis Freitas <mailto:lfreitas34 at yahoo.com>
> *To:* Alexei_Roudnev
> <mailto:Alexei_Roudnev at exigengroup.com> ; Brian Sieler
> <mailto:blsieler at gmail.com> ; ocfs2-users at oss.oracle.com
> <mailto:ocfs2-users at oss.oracle.com>
> *Sent:* Monday, April 09, 2007 2:29 PM
> *Subject:* Re: [Ocfs2-users] High on buffers and deep on swap
>
> Alexei,
> Yes, it seems to have no effect, which too is very
> strange. On 2.4 vm.freepages had a very easy to notice effect.
> There are other people having problems with buffers not
> being released on the list and some of them are forcing
> the kernel cache to be flushed with:
> echo 3 > /proc/sys/vm/drop_caches
> But I dont see this parameter on RHAS 4.0.
> Also, to be fair this seems to be a generic VM issue, I
> see this on servers that are not running ocfs2 too. And I
> only see this behavior on machines with more than 2Gb of
> memory.
> Regards,
> Luis
> Regards,
> Luis
>
> */Alexei_Roudnev <Alexei_Roudnev at exigengroup.com>/* wrote:
>
> Did you tried vm.swappiness parameter?
> (/proc/sys/vm/swappiness)
>
> -----
> Original Message -----
> *From:* Brian Sieler <mailto:blsieler at gmail.com>
> *To:* 'Luis Freitas' <mailto:lfreitas34 at yahoo.com>
> ; ocfs2-users at oss.oracle.com
> <mailto:ocfs2-users at oss.oracle.com>
> *Sent:* Sunday, April 08, 2007 10:52 PM
> *Subject:* RE: [Ocfs2-users] High on buffers and
> deep on swap
>
> Luis, yes I am experiencing what appears to be a
> similar problem you are describing. See my post
> from just a few minutes ago on another thread.
> I run a 2-node cluster with OCFS2/RAC on
> 2.6.9-34.0.2.ELsmp (RHEL 4.0) as well.
> total used free shared buffers cached
> Mem: 4044496 4005516 38980 0 34108 2236636
> -/+ buffers/cache: 1734772 2309724
> Swap: 2097144 648244 1448900
> If you’ve uncovered anything since posting this
> message, please pass it along?
> ------------------------------------------------------------------------
> *From:* ocfs2-users-bounces at oss.oracle.com
> [mailto:ocfs2-users-bounces at oss.oracle.com] *On
> Behalf Of *Luis Freitas
> *Sent:* Friday, February 23, 2007 5:32 PM
> *To:* ocfs2-users at oss.oracle.com
> *Subject:* [Ocfs2-users] High on buffers and deep
> on swap
> Hi,
> This is a bit off topic, hope there is not a problem.
> Anyone out there experiencing high swapping with
> the kernel retaining a large amount of buffers?
> This used to be a problem on 2.4, and I usually
> changed /proc/sys/vm/freepages to fix it. But on
> 2.6 this parameter no longer exists.
> One of the servers here is holding over 3.5Gb of
> cache even when using over 700Mb of swap, and free
> memory is always low.
> [oracle at br001sv0432 ~]$ free
> total used free shared buffers cached
> Mem: 5190736 4810880 379856 0 143032 3583868
> -/+ buffers/cache: 1083980 4106756
> Swap: 2048248 723064 1325184
> [oracle at br001sv0432 ~]$
> I am tuning /proc/sys/vm/swappiness, but this
> seems to have no effect at all. Changed from 60 to
> 10 and seems to have no effect. The server runs
> Oracle RAC with OCFS2.
> Regards,
> Luis
> ------------------------------------------------------------------------
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