linux-kernel - Re: VM/VFS bug with large amount of memory and file systems?

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Date:	Mon, 17 Sep 2007 15:04:05 +0100
From:	Anton Altaparmakov <aia21@....ac.uk>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	marc.smith@...ail.mcc.edu
Subject: Re: VM/VFS bug with large amount of memory and file systems?

On 15 Sep 2007, at 11:52, Andrew Morton wrote:
> On Sat, 15 Sep 2007 12:08:17 +0200 Peter Zijlstra  
> <peterz@...radead.org> wrote:
>> Anyway, looks like all of zone_normal is pinned in kernel  
>> allocations:
>>
>>> Sep 13 15:31:25 escabot Normal free:3648kB min:3744kB low:4680kB  
>>> high: 5616kB active:0kB inactive:3160kB present:894080kB  
>>> pages_scanned:5336 all_unreclaimable? yes
>>
>> Out of the 870 odd mb only 3 is on the lru.
>>
>> Would be grand it you could have a look at slabinfo and the like.
>
> Definitely.
>
>>> Sep 13 15:31:25 escabot free:1090395 slab:198893 mapped:988
>>> pagetables:129 bounce:0
>
> 814,665,728 bytes of slab.

Marc emailed me the contents of /proc/ 
{slabinfo,meminfo,vmstat,zoneinfo} taken just a few seconds before  
the machine panic()ed due to running OOM completely...  They files  
are attached this time rather than inlined so people don't complain  
about line wrapping!  (No doubt people will not complain about them  
being attached!  )-:)

If I read it correctly it appears all of low memory is eaten up by  
buffer_heads.

<quote>
# name            <active_objs> <num_objs> <objsize> <objperslab>  
<pagesperslab>
: tunables <limit> <batchcount> <sharedfactor> : slabdata  
<active_slabs> <num_s
labs> <sharedavail>
buffer_head       12569528 12569535     56   67    1 : tunables   
120   60    8 :
slabdata 187605 187605      0
</quote>

That is 671MiB of low memory in buffer_heads.

But why is the kernel not reclaiming them by getting rid of the page  
cache pages they are attached to or even leaving the pages around but  
killing their buffers?

I don't think I am doing anything in NTFS to cause this problem to  
happen...  Other than using buffer heads for my page cache pages that  
is but that is hardly a crime!  /-;

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/

View attachment "slabinfo.txt" of type "text/plain" (16276 bytes)

View attachment "meminfo.txt" of type "text/plain" (728 bytes)

View attachment "vmstat.txt" of type "text/plain" (808 bytes)

View attachment "zoneinfo.txt" of type "text/plain" (4284 bytes)