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Re: [RFC PATCH] index-pack: improve performance on NFS




On Thu, Nov 08, 2018 at 08:58:19PM +0000, Geert Jansen wrote:

> On Thu, Nov 08, 2018 at 07:02:57AM -0500, Jeff King wrote:
> 
> > Yes, testing and review. :)
> > 
> > I won't send the series out just yet, as I suspect it could use another
> > read-through on my part. But if you want to peek at it or try some
> > timings, it's available at:
> > 
> >   https://github.com/peff/git jk/loose-cache
> 
> I gave this branch a go. There's a performance regression as I'm getting a
> clone speed of about 100 KiB/s while with the previous patch I got around 20
> MiB/s. The culprint appears to be a very large number of stat() calls on
> ".git/objects/info/alternates". The call stack is:
> 
>  -> quick_has_loose()
>  -> prepare_alt_odb()
>  -> read_info_alternates()

Heh, indeed. Try this on top:

diff --git a/sha1-file.c b/sha1-file.c
index bc35b28e17..9ff27f92ed 100644
--- a/sha1-file.c
+++ b/sha1-file.c
@@ -692,6 +692,7 @@ void prepare_alt_odb(struct repository *r)
 	link_alt_odb_entries(r, r->objects->alternate_db, PATH_SEP, NULL, 0);
 
 	read_info_alternates(r, r->objects->odb->path, 0);
+	r->objects->loaded_alternates = 1;
 }
 
 /* Returns 1 if we have successfully freshened the file, 0 otherwise. */

-Peff