From: Jeff King <peff@peff.net>
To: Eric Sunshine <sunshine@sunshineco.com>
Cc: Git List <git@vger.kernel.org>
Subject: Re: [PATCH 4/6] strbuf: add an optimized 1-character strbuf_grow
Date: Mon, 6 Apr 2015 01:05:44 -0400 [thread overview]
Message-ID: <20150406050544.GB1932@peff.net> (raw)
In-Reply-To: <CAPig+cTK5MJLfwETFfM1Zdw35M2geKKmA6Q9M0kHdMP9t8qLNg@mail.gmail.com>
On Sun, Apr 05, 2015 at 10:13:21PM -0400, Eric Sunshine wrote:
> > - strbuf_grow(sb, 1);
> > + strbuf_grow_ch(sb);
>
> strbuf_grow_ch() seems overly special-case. What about instead taking
> advantage of inline strbuf_avail() to do something like this?
>
> if (!strbuf_avail())
> strbuf_grow(sb, 1);
Thanks, I somehow missed that function (despite it being a few line
above the one I added!).
I agree that strbuf_avail is a much better generic interface, and it
turns out to be just as fast (actually, a tiny bit faster in my tests).
I'll use that in the re-roll.
> (Minor tangent: The 1 is still slightly magical and potentially
> confusing for someone who doesn't know that the buffer is grown
> aggressively, so changing it to a larger number might make it more
> obvious to the casual reader that the buffer is in fact not being
> grown on every iteration.)
I agree this is slightly confusing (and I had to double-check how
strbuf_grow worked while writing this series). OTOH, this is not so much
about the "1" here as about how strbufs work. We care about the
amortized asymptotic cost. strbuf_add() has the same issue; we add more
bytes in each chunk, but we would still want to make sure that there is
a sub-linear relationship between the number of adds and the number of
allocations).
-Peff
next prev parent reply other threads:[~2015-04-06 5:06 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-05 1:06 [PATCH 0/6] address packed-refs speed regressions Jeff King
2015-04-05 1:07 ` [PATCH 1/6] strbuf_getwholeline: use getc macro Jeff King
2015-04-05 1:08 ` [PATCH 2/6] git-compat-util: add fallbacks for unlocked stdio Jeff King
2015-04-05 1:11 ` [PATCH 3/6] strbuf_getwholeline: use getc_unlocked Jeff King
2015-04-05 4:56 ` Jeff King
2015-04-05 5:27 ` Jeff King
2015-04-05 5:35 ` Jeff King
2015-04-05 20:49 ` Junio C Hamano
2015-04-05 14:36 ` Duy Nguyen
2015-04-05 18:24 ` Jeff King
2015-04-05 20:09 ` Junio C Hamano
2015-04-07 13:48 ` Rasmus Villemoes
2015-04-07 19:04 ` Jeff King
2015-04-07 22:43 ` Rasmus Villemoes
2015-04-08 0:17 ` Jeff King
2015-04-05 1:11 ` [PATCH 4/6] strbuf: add an optimized 1-character strbuf_grow Jeff King
2015-04-06 2:13 ` Eric Sunshine
2015-04-06 5:05 ` Jeff King [this message]
2015-04-05 1:11 ` [PATCH 5/6] t1430: add another refs-escape test Jeff King
2015-04-05 1:15 ` [PATCH 6/6] refname_is_safe: avoid expensive normalize_path_copy call Jeff King
2015-04-05 13:41 ` [PATCH 0/6] address packed-refs speed regressions René Scharfe
2015-04-05 18:52 ` Jeff King
2015-04-05 18:59 ` Jeff King
2015-04-05 23:04 ` René Scharfe
2015-04-05 22:39 ` René Scharfe
2015-04-06 4:49 ` Jeff King
2015-04-16 8:47 ` [PATCH v2 0/9] " Jeff King
2015-04-16 8:48 ` [PATCH 1/9] strbuf_getwholeline: use getc macro Jeff King
2015-04-16 8:48 ` [PATCH 2/9] git-compat-util: add fallbacks for unlocked stdio Jeff King
2015-04-16 8:49 ` [PATCH 3/9] strbuf_getwholeline: use getc_unlocked Jeff King
2015-04-16 8:51 ` [PATCH 4/9] config: use getc_unlocked when reading from file Jeff King
2015-04-16 8:53 ` [PATCH 5/9] strbuf_addch: avoid calling strbuf_grow Jeff King
2015-04-16 8:58 ` [PATCH 6/9] strbuf_getwholeline: " Jeff King
2015-04-16 9:01 ` [PATCH 7/9] strbuf_getwholeline: use getdelim if it is available Jeff King
2015-04-17 10:16 ` Eric Sunshine
2015-04-21 23:09 ` Jeff King
2015-05-08 23:56 ` Eric Sunshine
2015-05-09 1:09 ` Jeff King
2015-06-02 18:22 ` Eric Sunshine
2015-04-22 18:00 ` Johannes Schindelin
2015-04-22 18:06 ` Jeff King
2015-04-16 9:03 ` [PATCH 8/9] read_packed_refs: avoid double-checking sane refs Jeff King
2015-04-16 9:04 ` [PATCH 9/9] t1430: add another refs-escape test Jeff King
2015-04-16 9:25 ` [PATCH v2 0/9] address packed-refs speed regressions Jeff King
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