Patch is working fine, the server is stable.
Thanks for your support.
Brice GIBOUDEAU
> Hi,
>
> Thanks for all this informations.
> I'm testing an other solution, it's using a patch who increase the
> quantity of low memory.
> http://www.kernel.org/pub/linux/kernel/people/andrea/kernels/v2.4/2.4.23pre6aa3/00_3.5G-address-space-5
> http://lwn.net/Articles/39925/
>
> I will reply to this Email if the patch work correctly.
>
> Thx,
> Brice GIBOUDEAU
>
>
>
>> On Thu, Aug 04, 2005 at 10:53:38AM +0200, Brice GIBOUDEAU wrote:
>>> Hi,
>>>
>>> I give more details.
>>
>> Ta. Looks like lowmem exhaustion:
>>
>>> /proc/meminfo :
>>> ---------------
>>>
>>> Tue Aug 2 02:04:01 CEST 2005
>>> total: used: free: shared: buffers: cached:
>>> Mem: 16966471680 15623704576 1342767104 0 180224 14847438848
>>> Swap: 32737632256 0 32737632256
>>> MemTotal: 16568820 kB
>>> MemFree: 1311296 kB
>>> MemShared: 0 kB
>>> Buffers: 176 kB
>>> Cached: 14499452 kB
>>
>> Large page cache...
>>
>>> SwapCached: 0 kB
>>> Active: 1932 kB
>>> Inactive: 14497760 kB
>>
>> Mostly inactive...
>>
>>> HighTotal: 15858532 kB
>>> HighFree: 1305552 kB
>>> LowTotal: 710288 kB
>>> LowFree: 5744 kB
>>
>> And very little low memory free.
>>
>>> LowTotal: 710288 kB
>>> LowFree: 4788 kB
>>
>> Yup, not much there at all.
>>
>>> /proc/slabinfo :
>>> ----------------
>>>
>>> Tue Aug 2 02:04:02 CEST 2005
>>> slabinfo - version: 1.1 (SMP)
>>> xfs_inode 208657 208719 408 23191 23191 1 : 124 62
>>> linvfs_icache 208700 208700 384 20870 20870 1 : 124 62
>>> buffer_head 3624879 3751050 128 125034 125035 1 : 252 126
>>
>> So we have 80MiB in xfs inodes, another 80MiB in linvfs_icache, and
>> 460MiB in buffer heads. So that's a total of 620MiB of your 700MiB
>> of low memory right there, and probably the source of the memory
>> exhaustion.
>>
>> The buffer heads are the real problem - and that's related to the
>> size of the page cache. IIRC we have at least one buffer head per
>> page. With 14499452k of page cache, that's at least 3,624,863 buffer
>> heads needed at one per page. Looks pretty close, to me.
>>
>> This does look like a highmem/lowmem reclaim issue to me - the
>> pagecache in the highmem area needs to be reclaimed to free
>> up buffer heads in the lowmem region. because there is lots
>> of free memory in the highmem region, I doubt the reclaim
>> code is freeing it up sufficiently.
>>
>> One quick thing to try is limit the machine to, say, 12GiB of RAM
>> (mem=xxx boot option) and that will limit buffer head usage to less
>> that 400MiB of low memory. That should prevent you from exhausting
>> lowmem by bounding the maximum size of the kernel pagecache at
>> a point below where lowmem exhaustion occurs.
>>
>> Another option is to go to a 2.6 kernel as, IIRC, XFS no longer
>> has the buffer-head-per-cached-page behaviour in 2.6. Hence you
>> won't consume anywhere near as much lowmem on a 2.6 kernel when
>> the kernel lets the page cache grow so large....
>>
>> Yet another option is to move to a 64bit platform that doesn't have
>> this lowmem/highmem memory architecture...
>>
>> HTH.
>>
>> Cheers,
>>
>> Dave.
>> --
>> Dave Chinner
>> R&D Software Enginner
>> SGI Australian Software Group
>>
>
>
>
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