[PATCH 2/2] sha1_file: only freshen packs once per run
- From
Jeff King <peff@peff.net>
- Date
- Apr 20, 2015, 19:55 UTC
- Message-ID
- <20150420195500.GB15760@peff.net>
- In-Reply-To
- <20150420195337.GA15447@peff.net>
Since 33d4221 (write_sha1_file: freshen existing objects, 2014-10-15), we update the mtime of existing objects that we would have written out (had they not existed). For the common case in which many objects are packed, we may update the mtime on a single packfile repeatedly. This can result in a noticeable performance problem if calling utime() is expensive (e.g., because your storage is on NFS).
We can fix this by keeping a per-pack flag that lets us freshen only once per program invocation.
An alternative would be to keep the packed_git.mtime flag up to date as we freshen, and freshen only once every N seconds. In practice, it's not worth the complexity. We are racing against prune expiration times here, which inherently must be set to accomodate reasonable program running times (because they really care about the time between an object being written and it becoming referenced, and the latter is typically the last step a program takes).
Signed-off-by: Jeff King <peff@peff.net> --- Hopefully I didn't botch the flag logic again. :) I tested with "strace -c" myself this time, so I think it is good.
cache.h | 1 + sha1_file.c | 9 ++++++++- 2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/cache.h b/cache.h index 3d3244b..72c6888 100644 --- a/cache.h +++ b/cache.h @@ -1174,6 +1174,7 @@ extern struct packed_git { int pack_fd; unsigned pack_local:1, pack_keep:1, + freshened:1, do_not_close:1; unsigned char sha1[20]; /* something like ".git/objects/pack/xxxxx.pack" */ diff --git a/sha1_file.c b/sha1_file.c index 822aaef..26b9b2b 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -2999,7 +2999,14 @@ static int freshen_loose_object(const unsigned char *sha1) static int freshen_packed_object(const unsigned char *sha1) { struct pack_entry e; - return find_pack_entry(sha1, &e) && freshen_file(e.p->pack_name); + if (!find_pack_entry(sha1, &e)) + return 0; + if (e.p->freshened) + return 1; + if (!freshen_file(e.p->pack_name)) + return 0; + e.p->freshened = 1; + return 1; } int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
-- 2.4.0.rc2.384.g7297a4a