From: Tay Ray Chuan <rctay89@gmail.com>
To: Shawn Pearce <spearce@spearce.org>
Cc: Git Mailing List <git@vger.kernel.org>
Subject: Re: [RFC/PATCH 0/3] teach --histogram to diff
Date: Thu, 14 Jul 2011 00:34:14 +0800 [thread overview]
Message-ID: <CALUzUxqS8y4HH44t2CuSvfQiLP-Y7hFtbi5x2rtAwPBKSJ+3Bw@mail.gmail.com> (raw)
In-Reply-To: <CAJo=hJu5ubkzUyyPM0nqP+J9CU3hBtAHfuzaLSuN214Hux4qTA@mail.gmail.com>
On Tue, Jul 12, 2011 at 10:19 PM, Shawn Pearce <spearce@spearce.org> wrote:
> On Mon, Jul 11, 2011 at 23:10, Tay Ray Chuan <rctay89@gmail.com> wrote:
>> [RFC/PATCH 3/3] xdiff/xprepare: use a smaller sample size for histogram
>
> Do we need sampling at all for histogram? Can you skip it?
Sampling is done to get a guess of lines in the file. This guess is
then used to preallocated memory for the list of records. (This is
just a guess; if we find more records we allocate more memory.) By
doing this preallocation, we can save on malloc()'s, giving a
performance boost.
But then sampling has its costs - previously, we ran up to 256
memchr('\n')s within a mmfile "block". For histogram diff, we cut the
cap down to 20. (But not for the other diff algorithms - see the
relevant patch text for more.) I think this gives us a good balance -
time spent in guessing lines, and time gained from preallocating
memory.
--
Cheers,
Ray Chuan
next prev parent reply other threads:[~2011-07-13 16:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-12 6:10 [RFC/PATCH 0/3] teach --histogram to diff Tay Ray Chuan
2011-07-12 6:10 ` [RFC/PATCH 1/3] " Tay Ray Chuan
2011-07-12 6:10 ` [RFC/PATCH 2/3] xdiff/xprepare: skip classification Tay Ray Chuan
2011-07-12 6:10 ` [RFC/PATCH 3/3] xdiff/xprepare: use a smaller sample size for histogram diff Tay Ray Chuan
2011-07-12 19:56 ` [RFC/PATCH 1/3] teach --histogram to diff Junio C Hamano
2011-07-13 16:36 ` Tay Ray Chuan
2011-07-12 14:19 ` [RFC/PATCH 0/3] " Shawn Pearce
2011-07-12 17:43 ` Junio C Hamano
2011-07-13 16:35 ` Tay Ray Chuan
2011-07-13 16:34 ` Tay Ray Chuan [this message]
2011-08-01 3:16 ` [PATCH v2 0/8] " Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 1/8] xdiff/xprepare: use memset() Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 2/8] do away with xdl_mmfile_next() Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 3/8] xdiff/xprepare: refactor abort cleanups Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 4/8] xdiff/xpatience: factor out fall-back-diff function Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 5/8] t4033-diff-patience: factor out tests Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 6/8] teach --histogram to diff Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 7/8] xdiff/xprepare: skip classification Tay Ray Chuan
2011-08-01 3:16 ` [PATCH v2 8/8] xdiff/xprepare: use a smaller sample size for histogram diff Tay Ray Chuan
2011-08-01 4:20 ` [PATCH 0/4] changes for rc/histogram-diff in 'next' Tay Ray Chuan
2011-08-01 4:20 ` [PATCH 1/4] xdiff: do away with xdl_mmfile_next() Tay Ray Chuan
2011-08-01 4:20 ` [PATCH 2/4] xdiff/xhistogram: rework handling of recursed results Tay Ray Chuan
2011-08-01 4:20 ` [PATCH 3/4] xdiff/xhistogram: rely on xdl_trim_ends() Tay Ray Chuan
2011-08-01 4:20 ` [PATCH 4/4] xdiff/xhistogram: drop need for additional variable Tay Ray Chuan
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