[sheepdog] [PATCH] sheep: cache sha1 digest for read-only objects

[MORITA Kazutaka]

At Tue, 14 May 2013 15:14:05 +0800,
Liu Yuan wrote:
> 
> > The contents of read-only objects are immutable.  We can cache their
> > sha1 digests as extended attributes for the next sha1 calculation.
> > With this patch, I can complete 'collie vdi check' of a 4 GB snapshot
> > volume in 0.2 seconds.
> 
> Any number for recovery boost?

Not tested yet.  I'll send the result later, but note that we can gain
the performance boost only against read-only (snapshot) objects.  We
cannot cache sha1 digests of stale objects blindly because they may be
hard-linked to the writable objects in the working directory.

Thanks,

Kazutaka