[Lustre-discuss] very slow directory access (lstat taking >20s to return)

Daniel Kobras kobras at linux.de
Fri Oct 29 06:20:37 PDT 2010


Hi Frederik!

On Fri, Oct 29, 2010 at 09:40:33AM +0100, Frederik Ferner wrote:
> Doing a 'strace -T -e file ls -n' on one directory with about 750 files, 
> while users were seeing the hanging ls, showed lstat calls taking 
> seconds, up to 23s.

The (l)stat() calls determine the exact size of all files in the displayed
directory. This means that each OSTs needs to revoke client write locks for all
these files, ie. client-side write caches for all files in the directory are
flushed before the (l)stat() returns. This can easily take several seconds if
there is heavy write activity on the file.

Regards,

Daniel.



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