From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 06/12] clone: disable save_commit_buffer
Date: Wed, 25 Jan 2017 14:27:40 -0500 [thread overview]
Message-ID: <20170125192740.5lqoc2srqfjiyfwr@sigill.intra.peff.net> (raw)
In-Reply-To: <xmqqmvefaray.fsf@gitster.mtv.corp.google.com>
On Wed, Jan 25, 2017 at 11:11:01AM -0800, Junio C Hamano wrote:
> Jeff King <peff@peff.net> writes:
>
> > Normally git caches the raw commit object contents in
> > "struct commit". This makes it fast to run parse_commit()
> > followed by a pretty-print operation.
> >
> > For commands which don't actually pretty-print the commits,
> > the caching is wasteful (and may use quite a lot of memory
> > if git accesses a large number of commits).
> >
> > For fetching operations like clone, we already disable
>
> s/clone/fetch/ you meant?
Well, no, because this patch deals with clone.
It's likely that builtin/fetch.c would want the same treatment. It
didn't come up for me because I've disabled the alternates check for
that case (but you can't do that with stock git), and I didn't dig
further.
Possibly this should just go into fetch-pack.c, right before we walk
over all of the refs and call parse_object() and deref_tag() on all of
them. It feels a little funny to tweak the global save_commit_buffer
flag there, but it already do so in everything_local(), so I don't think
we're really losing much.
> > In one real-world case with a large number of tags, this
> > cut about 10MB off of clone's heap usage. Not spectacular,
> > but there's really no downside.
>
> "There is no downside" is especially true in the modern world post
> v2.1, where get_commit_buffer() is what everybody has to go through
> to access this information. I would have been very hesitant to
> accept a patch like this one if we didn't do that clean-up, as a
> stray codepath could have just done "commit->buffer" and segfaulted
> or said "ah, there is no message", neither of which is satisfactory.
Yep, I had a similar thought while writing it. I would have been very
hesitant to propose it back then, too. :)
-Peff
next prev parent reply other threads:[~2017-01-25 19:27 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-24 0:37 [PATCH 0/12] reducing resource usage of for_each_alternate_ref Jeff King
2017-01-24 0:38 ` [PATCH 01/12] for_each_alternate_ref: handle failure from real_pathdup() Jeff King
2017-01-25 18:26 ` Junio C Hamano
2017-01-24 0:39 ` [PATCH 02/12] for_each_alternate_ref: stop trimming trailing slashes Jeff King
2017-01-24 0:40 ` [PATCH 03/12] for_each_alternate_ref: use strbuf for path allocation Jeff King
2017-01-25 18:29 ` Junio C Hamano
2017-01-25 18:40 ` Jeff King
2017-01-24 0:40 ` [PATCH 04/12] for_each_alternate_ref: pass name/oid instead of ref struct Jeff King
2017-01-24 0:44 ` [PATCH 05/12] for_each_alternate_ref: replace transport code with for-each-ref Jeff King
2017-01-25 19:00 ` Junio C Hamano
2017-01-24 0:45 ` [PATCH 06/12] clone: disable save_commit_buffer Jeff King
2017-01-25 19:11 ` Junio C Hamano
2017-01-25 19:27 ` Jeff King [this message]
2017-01-25 19:35 ` Jeff King
2017-01-25 21:07 ` Jeff King
2017-01-24 0:45 ` [PATCH 07/12] fetch-pack: cache results of for_each_alternate_ref Jeff King
2017-01-25 19:21 ` Junio C Hamano
2017-01-25 19:47 ` Jeff King
2017-01-24 0:46 ` [PATCH 08/12] add oidset API Jeff King
2017-01-24 20:26 ` Ramsay Jones
2017-01-24 20:35 ` Jeff King
2017-01-24 0:47 ` [PATCH 09/12] receive-pack: use oidset to de-duplicate .have lines Jeff King
2017-01-25 19:32 ` Junio C Hamano
2017-01-25 19:54 ` Jeff King
2017-01-24 0:47 ` [PATCH 10/12] receive-pack: fix misleading namespace/.have comment Jeff King
2017-01-24 0:48 ` [PATCH 11/12] receive-pack: treat namespace .have lines like alternates Jeff King
2017-01-25 19:51 ` Junio C Hamano
2017-01-25 19:58 ` Jeff King
2017-01-27 17:45 ` Lukas Fleischer
2017-01-27 17:58 ` Jeff King
2017-01-27 20:42 ` Junio C Hamano
2017-01-24 0:48 ` [PATCH 12/12] receive-pack: avoid duplicates between our refs and alternates Jeff King
2017-01-25 20:02 ` Junio C Hamano
2017-01-25 20:05 ` Jeff King
2017-01-24 1:33 ` [PATCH 0/12] reducing resource usage of for_each_alternate_ref Brandon Williams
2017-01-24 2:12 ` Jeff King
2017-02-08 20:52 ` [PATCH v2 0/11] " Jeff King
2017-02-08 20:52 ` [PATCH v2 01/11] for_each_alternate_ref: handle failure from real_pathdup() Jeff King
2017-02-08 20:52 ` [PATCH v2 02/11] for_each_alternate_ref: stop trimming trailing slashes Jeff King
2017-02-08 20:52 ` [PATCH v2 03/11] for_each_alternate_ref: use strbuf for path allocation Jeff King
2017-02-08 20:52 ` [PATCH v2 04/11] for_each_alternate_ref: pass name/oid instead of ref struct Jeff King
2017-02-08 20:53 ` [PATCH v2 05/11] for_each_alternate_ref: replace transport code with for-each-ref Jeff King
2017-02-08 20:53 ` [PATCH v2 06/11] fetch-pack: cache results of for_each_alternate_ref Jeff King
2017-02-08 20:53 ` [PATCH v2 07/11] add oidset API Jeff King
2017-02-08 20:53 ` [PATCH v2 08/11] receive-pack: use oidset to de-duplicate .have lines Jeff King
2017-02-08 20:53 ` [PATCH v2 09/11] receive-pack: fix misleading namespace/.have comment Jeff King
2017-02-08 20:53 ` [PATCH v2 10/11] receive-pack: treat namespace .have lines like alternates Jeff King
2017-02-08 20:53 ` [PATCH v2 11/11] receive-pack: avoid duplicates between our refs and alternates Jeff King
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