Re: [PATCH] unpack-trees: fix accidentally quadratic behavior

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, 2016-01-20 at 20:58 -0800, Junio C Hamano wrote:
> David Turner <dturner@xxxxxxxxxxxxxxxx> writes:
> 
> > While unpacking trees (e.g. during git checkout), when we hit a
> > cache
> > entry that's past and outside our path, we cut off iteration.
> > 
> > This provides about a 45% speedup on git checkout between master
> > and
> > master^20000 on Twitter's monorepo.  Speedup in general will depend
> > on
> > repostitory structure, number of changes, and packfile packing
> > decisions.
> > 
> > Signed-off-by: David Turner <dturner@xxxxxxxxxxxxxxxx>
> > ---
> 
> I haven't thought things through, but does this get fooled by the
> somewhat strange ordering rules of tree entries (i.e. a subtree
> sorts as if its name is suffixed with a '/' in a tree object)?
> 
> Other than that, I like this.  "We know the list is sorted, and
> after seeing this entry we know there is nothing that will match" is
> an obvious optimization that we already use elsewhere.
> 
> Thanks.

I think this is correct, because we first do the more complicated check
(ce_in_traverse_path), and only check the ordering once that has
failed.  The tests all pass, so this should be good.
--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Kernel Development]     [Gcc Help]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [V4L]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]     [Fedora Users]