From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Geoffrey Irving <irving@naml.us>
Cc: Jeff King <peff@peff.net>, "git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: [PATCH] Adding a cache of commit to patch-id pairs to speed up git-cherry
Date: Mon, 2 Jun 2008 19:15:09 +0100 (BST) [thread overview]
Message-ID: <alpine.DEB.1.00.0806021913340.13507@racer.site.net> (raw)
In-Reply-To: <7f9d599f0806020926j7ac9fb12jefa5a14fe5708226@mail.gmail.com>
Hi,
On Mon, 2 Jun 2008, Geoffrey Irving wrote:
> On Mon, Jun 2, 2008 at 9:18 AM, Johannes Schindelin
> <Johannes.Schindelin@gmx.de> wrote:
>
> > On Mon, 2 Jun 2008, Geoffrey Irving wrote:
> >
> >> On Mon, Jun 2, 2008 at 8:37 AM, Johannes Schindelin
> >> <Johannes.Schindelin@gmx.de> wrote:
> >>
> >> > Another issue that just hit me: this cache is append-only, so if it
> >> > grows too large, you have no other option than to scratch and
> >> > recreate it. Maybe this needs porcelain support, too? (git gc?)
> >>
> >> If so, the correct operation is to go through the hash and remove
> >> entries that refer to commits that no longer exist. I can add this
> >> if you want. Hopefully somewhere along the way git-gc constructs an
> >> easy to traverse list of extant commits, and this will be
> >> straightforward.
> >
> > I don't know... if you have created a cached patch-id for every commit
> > (by mistake, for example) and do not need it anymore, it might make
> > git-cherry substantially faster to just scrap the cache.
>
> Well, ideally hash maps are O(1), but it could be a difference between a
> "compare 40 bytes" constant and a "read a 4k block into memory"
> constant, so in practice yes. Scrapping it entirely will also make the
> implementation much simpler.
>
> It seems a little sad to wipe all that effort each time, but
> regenerating the cache is likely to be less expensive than a git-gc, so
> it shouldn't change any amortized complexities.
Well, how about only scrapping the cache if it is older than, say, 2
weeks, and is larger than, say, 200kB? That should help.
Ciao,
Dscho
next prev parent reply other threads:[~2008-06-02 18:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-02 3:54 [PATCH] Adding a cache of commit to patch-id pairs to speed up git-cherry Geoffrey Irving
2008-06-02 6:13 ` Johannes Schindelin
2008-06-02 6:42 ` Jeff King
2008-06-02 14:35 ` Geoffrey Irving
2008-06-02 15:37 ` Johannes Schindelin
2008-06-02 15:49 ` Geoffrey Irving
2008-06-02 15:56 ` Shawn O. Pearce
2008-06-02 16:18 ` Johannes Schindelin
2008-06-02 16:26 ` Geoffrey Irving
2008-06-02 18:15 ` Johannes Schindelin [this message]
2008-06-07 23:50 ` Geoffrey Irving
2008-06-08 16:10 ` Johannes Schindelin
2008-06-02 14:50 ` Geoffrey Irving
2008-06-02 15:52 ` Johannes Schindelin
2008-06-02 17:23 ` Geoffrey Irving
2008-06-02 18:22 ` Johannes Schindelin
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