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Re: Slab memory usage

To: xfs@xxxxxxxxxxx
Subject: Re: Slab memory usage
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Sun, 26 Apr 2009 23:51:22 +0200
In-reply-to: <49F260F1.4030503@xxxxxxxxxxx>
Organization: it-management http://it-management.at
References: <73EE3FB2-381F-43F1-82C1-FA4C020E7C02@xxxxxxxxxxx> <49F260F1.4030503@xxxxxxxxxxx>
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On Samstag 25 April 2009 Eric Sandeen wrote:
> *from Documentation/sysctl/vm.txt:
> vfs_cache_pressure
> ------------------
> Controls the tendency of the kernel to reclaim the memory which is
> used for caching of directory and inode objects.
> At the default value of vfs_cache_pressure=100 the kernel will
> attempt to reclaim dentries and inodes at a "fair" rate with respect
> to pagecache and swapcache reclaim.  Decreasing vfs_cache_pressure
> causes the kernel to prefer to retain dentry and inode caches.
>  Increasing vfs_cache_pressure beyond 100 causes the kernel to prefer
> to reclaim dentries and inodes.

So if I decrease it, lets say to 60, Linux prefers to remember 
files/dirs over their content. An increase to 150 would mean Linux 
prefers to keep file contents over dirs/files?

If so, I think for a fileserver for many users accessing many 
dirs/files, I'd prefer a lower value, in order to prevent searching. 
Disk contents can be read fast, with all the read-ahead caching of 
disks/controllers and Linux itself, but the scattered dirs take loooong 
to scan sometimes. (Example: a foto collection with 50.000 files in many 
dirs). Am I right?

mfg zmi
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