[Lustre-discuss] Lustre buffer cache causes large system overhead.

Scott Nolin scott.nolin at ssec.wisc.edu
Fri Aug 23 07:56:29 PDT 2013

I forgot to add 'slabtop' is a nice tool for watching this stuff.


On 8/23/2013 9:36 AM, Scott Nolin wrote:
> You might also try increasing the vfs_cache_pressure.
> This will reclaim inode and dentry caches faster. Maybe that's the
> problem, not page caches.
> To be clear - I have no deep insight into Lustre's use of the client
> cache, but you said you has lots of small files, which if lustre uses
> the cache system like other filesystems means it may be inodes/dentries.
> Filling up the page cache with files like you did in your other tests
> wouldn't have the same effect. Just my guess here.
> We had some experience years ago with the opposite sort of problem. We
> have a big ftp server, and we want to *keep* inode/dentry data in the
> linux cache, as there are often stupid numbers of files in directories.
> Files were always flowing through the server, so the page cache would
> force out the inode cache. Was surprised to find with linux there's no
> ability to set a fixed inode cache size - the best you can do is
> "suggest" with the cache pressure tunable.
> Scott
> On 8/23/2013 6:29 AM, Dragseth Roy Einar wrote:
>> I tried to change swapiness from 0 to 95 but it did not have any
>> impact on the
>> system overhead.
>> r.

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