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Re: OOM on quotacheck (again?)

Subject: Re: OOM on quotacheck (again?)
From: Volker <mail@xxxxxxxxxx>
Date: Mon, 24 Sep 2012 16:47:25 +0200
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120924132113.GL20960@dastard>
References: <5059D2B4.8010300@xxxxxxxxxx> <20120919205924.GC31501@dastard> <505AE2A1.5060703@xxxxxxxxxx> <20120924132113.GL20960@dastard>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:15.0) Gecko/20120907 Thunderbird/15.0.1
Hi,

>> Could you slightly elaborate on that or give me a link or two which
>> explain the matter?
> 
> The kernel segment is limited to 960MB of RAM on ia32 bit machines
> unless you build with special config options that allow for up to
> 3GB of kernel memory. The trade off is that you've only got 4GB of
> RAM in teh process address space, so by default you have 3GB of RAM
> for each process (i.e. 960MB/3GB kernel/user split). If you change
> that to a 3GB/1GB split, you'll have problems with applications
> that are memory hogs running out of memory.

Interesting!

> As to the memory used by the inode cache, inodes tend to use between
> 1-1.5k of RAM each. Hence for a 960MB kernel segment, you *might* be
> able to cache 500,000 inodes if you don't cache anything else.
> Typically it will be 25-30% of that number (200-300MB of RAM in
> caching inodes during filesystem traversal). Seeing as you have
> millions of inodes, that's way more than you can cache in available
> kernel memory... 

Great! That answered all my questions! Thanks a lot!

3.6.0-rc6-x64 ist currently running fine on 6 machines.

-volker

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