Re: Very aggressive memory reclaim

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* Re: Very aggressive memory reclaim
       [not found] <AANLkTinFqqmE+fTMTLVU-_CwPE+LQv7CpXSQ5+CdAKLK@mail.gmail.com>
@ 2011-03-28 21:53 ` Dave Chinner
  2011-03-28 22:52   ` Minchan Kim
                     ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Dave Chinner @ 2011-03-28 21:53 UTC (permalink / raw)
  To: John Lepikhin; +Cc: linux-mm, linux-kernel, xfs

[cc xfs and mm lists]

On Mon, Mar 28, 2011 at 08:39:29PM +0400, John Lepikhin wrote:
> Hello,
> 
> I use high-loaded machine with 10M+ inodes inside XFS, 50+ GB of
> memory, intensive HDD traffic and 20..50 forks per second. Vanilla
> kernel 2.6.37.4. The problem is that kernel frees memory very
> aggressively.
> 
> For example:
> 
> 25% of memory is used by processes
> 50% for page caches
> 7% for slabs, etc.
> 18% free.
> 
> That's bad but works. After few hours:
> 
> 25% of memory is used by processes
> 62% for page caches
> 7% for slabs, etc.
> 5% free.
> 
> Most of files are cached, works perfectly. This is the moment when
> kernel decides to free some memory. After memory reclaim:
> 
> 25% of memory is used by processes
> 25% for page caches(!)
> 7% for slabs, etc.
> 43% free(!)
> 
> Page cache is dropped, server becomes too slow. This is the beginning
> of new cycle.
> 
> I didn't found any huge mallocs at that moment. Looks like because of
> large number of small mallocs (forks) kernel have pessimistic forecast
> about future memory usage and frees too much memory. Is there any
> options of tuning this? Any other variants?

First it would be useful to determine why the VM is reclaiming so
much memory. If it is somewhat predictable when the excessive
reclaim is going to happen, it might be worth capturing an event
trace from the VM so we can see more precisely what it is doiing
during this event. In that case, recording the kmem/* and vmscan/*
events is probably sufficient to tell us what memory allocations
triggered reclaim and how much reclaim was done on each event.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-28 21:53 ` Very aggressive memory reclaim Dave Chinner
@ 2011-03-28 22:52   ` Minchan Kim
  2011-03-29  2:55     ` KOSAKI Motohiro
  2011-03-29  7:22     ` John Lepikhin
  2011-03-28 23:58   ` Andi Kleen
  2011-03-29  7:26   ` John Lepikhin
  2 siblings, 2 replies; 9+ messages in thread
From: Minchan Kim @ 2011-03-28 22:52 UTC (permalink / raw)
  To: Dave Chinner; +Cc: linux-mm, John Lepikhin, linux-kernel, xfs

On Tue, Mar 29, 2011 at 6:53 AM, Dave Chinner <david@fromorbit.com> wrote:
> [cc xfs and mm lists]
>
> On Mon, Mar 28, 2011 at 08:39:29PM +0400, John Lepikhin wrote:
>> Hello,
>>
>> I use high-loaded machine with 10M+ inodes inside XFS, 50+ GB of
>> memory, intensive HDD traffic and 20..50 forks per second. Vanilla
>> kernel 2.6.37.4. The problem is that kernel frees memory very
>> aggressively.
>>
>> For example:
>>
>> 25% of memory is used by processes
>> 50% for page caches
>> 7% for slabs, etc.
>> 18% free.
>>
>> That's bad but works. After few hours:
>>
>> 25% of memory is used by processes
>> 62% for page caches
>> 7% for slabs, etc.
>> 5% free.
>>
>> Most of files are cached, works perfectly. This is the moment when
>> kernel decides to free some memory. After memory reclaim:
>>
>> 25% of memory is used by processes
>> 25% for page caches(!)
>> 7% for slabs, etc.
>> 43% free(!)
>>
>> Page cache is dropped, server becomes too slow. This is the beginning
>> of new cycle.
>>
>> I didn't found any huge mallocs at that moment. Looks like because of
>> large number of small mallocs (forks) kernel have pessimistic forecast
>> about future memory usage and frees too much memory. Is there any
>> options of tuning this? Any other variants?
>
> First it would be useful to determine why the VM is reclaiming so
> much memory. If it is somewhat predictable when the excessive
> reclaim is going to happen, it might be worth capturing an event
> trace from the VM so we can see more precisely what it is doiing
> during this event. In that case, recording the kmem/* and vmscan/*
> events is probably sufficient to tell us what memory allocations
> triggered reclaim and how much reclaim was done on each event.
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
>

Recently, We had a similar issue.
http://www.spinics.net/lists/linux-mm/msg12243.html
But it seems to not merge. I don't know why since I didn't follow up the thread.
Maybe Cced guys can help you.

Is it a sudden big cache drop at the moment or accumulated small cache
drop for long time?
What's your zones' size?

Please attach the result of cat /proc/zoneinfo for others.

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-28 22:52   ` Minchan Kim
@ 2011-03-29  2:55     ` KOSAKI Motohiro
  2011-03-29  7:33       ` John Lepikhin
  2011-03-29  7:22     ` John Lepikhin
  1 sibling, 1 reply; 9+ messages in thread
From: KOSAKI Motohiro @ 2011-03-29  2:55 UTC (permalink / raw)
  To: Minchan Kim; +Cc: linux-kernel, xfs, linux-mm, John Lepikhin, kosaki.motohiro

> Recently, We had a similar issue.
> http://www.spinics.net/lists/linux-mm/msg12243.html
> But it seems to not merge. I don't know why since I didn't follow up the thread.
> Maybe Cced guys can help you.
> 
> Is it a sudden big cache drop at the moment or accumulated small cache
> drop for long time?
> What's your zones' size?
> 
> Please attach the result of cat /proc/zoneinfo for others.

If my remember is correct, 2.6.38 is included Mel's anti agressive 
reclaim patch. And original report seems to be using 2.6.37.x. 

John, can you try 2.6.38?



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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-29  2:55     ` KOSAKI Motohiro
@ 2011-03-29  7:33       ` John Lepikhin
  0 siblings, 0 replies; 9+ messages in thread
From: John Lepikhin @ 2011-03-29  7:33 UTC (permalink / raw)
  To: KOSAKI Motohiro; +Cc: linux-mm, xfs, Minchan Kim, linux-kernel

2011/3/29 KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>:

> If my remember is correct, 2.6.38 is included Mel's anti agressive
> reclaim patch. And original report seems to be using 2.6.37.x.
>
> John, can you try 2.6.38?

I'll ask my boss about it. Unfortunately we found opposite issue with
memory management + XFS (100M of inodes) on 2.6.38: some objects in
xfs_inode and dentry slabs are seems to be never cleared (at least
without "sync && echo 2 >.../drop_caches"). But this is not a
production machine working 24x7, so we don't care about it right now.

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-28 22:52   ` Minchan Kim
  2011-03-29  2:55     ` KOSAKI Motohiro
@ 2011-03-29  7:22     ` John Lepikhin
  1 sibling, 0 replies; 9+ messages in thread
From: John Lepikhin @ 2011-03-29  7:22 UTC (permalink / raw)
  To: Minchan Kim; +Cc: linux-mm, linux-kernel, xfs

[-- Attachment #1: Type: text/plain, Size: 204 bytes --]

2011/3/29 Minchan Kim <minchan.kim@gmail.com>:

> Please attach the result of cat /proc/zoneinfo for others.

See attachment. Right now I have no zoneinfo for crisis time, but I
can catch it if required.

[-- Attachment #2: zoneinfo --]
[-- Type: application/octet-stream, Size: 14655 bytes --]

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[-- Attachment #3: meminfo --]
[-- Type: application/octet-stream, Size: 1015 bytes --]

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DirectMap1G:    97517568 kB

[-- Attachment #4: Type: text/plain, Size: 121 bytes --]

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-28 21:53 ` Very aggressive memory reclaim Dave Chinner
  2011-03-28 22:52   ` Minchan Kim
@ 2011-03-28 23:58   ` Andi Kleen
  2011-03-29  1:57     ` Dave Chinner
  2011-03-29  7:26   ` John Lepikhin
  2 siblings, 1 reply; 9+ messages in thread
From: Andi Kleen @ 2011-03-28 23:58 UTC (permalink / raw)
  To: Dave Chinner; +Cc: linux-mm, John Lepikhin, linux-kernel, xfs

Dave Chinner <david@fromorbit.com> writes:
>
> First it would be useful to determine why the VM is reclaiming so
> much memory. If it is somewhat predictable when the excessive
> reclaim is going to happen, it might be worth capturing an event

Often it's to get pages of a higher order. Just tracing alloc_pages
should tell you that.

There are a few other cases (like memory failure handling), but they're
more obscure.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-28 23:58   ` Andi Kleen
@ 2011-03-29  1:57     ` Dave Chinner
  0 siblings, 0 replies; 9+ messages in thread
From: Dave Chinner @ 2011-03-29  1:57 UTC (permalink / raw)
  To: Andi Kleen; +Cc: linux-mm, John Lepikhin, linux-kernel, xfs

On Mon, Mar 28, 2011 at 04:58:50PM -0700, Andi Kleen wrote:
> Dave Chinner <david@fromorbit.com> writes:
> >
> > First it would be useful to determine why the VM is reclaiming so
> > much memory. If it is somewhat predictable when the excessive
> > reclaim is going to happen, it might be worth capturing an event
> 
> Often it's to get pages of a higher order. Just tracing alloc_pages
> should tell you that.

Yes, the kmem/mm_page_alloc tracepoint gives us that. But in case
that is not the cause, grabbing all the trace points I suggested is
more likely to indicate where the problem is. I'd prefer to get more
data than needed the first time around than have to do multiple
round trips because a single trace point doesn't tell us the cause...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-28 21:53 ` Very aggressive memory reclaim Dave Chinner
  2011-03-28 22:52   ` Minchan Kim
  2011-03-28 23:58   ` Andi Kleen
@ 2011-03-29  7:26   ` John Lepikhin
  2011-03-29  8:59     ` Avi Kivity
  2 siblings, 1 reply; 9+ messages in thread
From: John Lepikhin @ 2011-03-29  7:26 UTC (permalink / raw)
  To: Dave Chinner; +Cc: linux-mm, linux-kernel, xfs

2011/3/29 Dave Chinner <david@fromorbit.com>:

> First it would be useful to determine why the VM is reclaiming so
> much memory. If it is somewhat predictable when the excessive
> reclaim is going to happen, it might be worth capturing an event
> trace from the VM so we can see more precisely what it is doiing
> during this event. In that case, recording the kmem/* and vmscan/*
> events is probably sufficient to tell us what memory allocations
> triggered reclaim and how much reclaim was done on each event.

Do you mean I must add some debug to mm functions? I don't know any
other way to catch such events.

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^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: Very aggressive memory reclaim
  2011-03-29  7:26   ` John Lepikhin
@ 2011-03-29  8:59     ` Avi Kivity
  0 siblings, 0 replies; 9+ messages in thread
From: Avi Kivity @ 2011-03-29  8:59 UTC (permalink / raw)
  To: John Lepikhin; +Cc: linux-mm, linux-kernel, xfs

On 03/29/2011 09:26 AM, John Lepikhin wrote:
> 2011/3/29 Dave Chinner<david@fromorbit.com>:
>
> >  First it would be useful to determine why the VM is reclaiming so
> >  much memory. If it is somewhat predictable when the excessive
> >  reclaim is going to happen, it might be worth capturing an event
> >  trace from the VM so we can see more precisely what it is doiing
> >  during this event. In that case, recording the kmem/* and vmscan/*
> >  events is probably sufficient to tell us what memory allocations
> >  triggered reclaim and how much reclaim was done on each event.
>
> Do you mean I must add some debug to mm functions? I don't know any
> other way to catch such events.

Download and build trace-cmd 
(git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git), 
and do

$ trace-cmd record -e kmem -e vmscan -b 30000

Hit ctrl-C when done and post the output file generated in cwd.

-- 
error compiling committee.c: too many arguments to function

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^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2011-03-29  8:56 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
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2011-03-28 21:53 ` Very aggressive memory reclaim Dave Chinner
2011-03-28 22:52   ` Minchan Kim
2011-03-29  2:55     ` KOSAKI Motohiro
2011-03-29  7:33       ` John Lepikhin
2011-03-29  7:22     ` John Lepikhin
2011-03-28 23:58   ` Andi Kleen
2011-03-29  1:57     ` Dave Chinner
2011-03-29  7:26   ` John Lepikhin
2011-03-29  8:59     ` Avi Kivity

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