From: Junio C Hamano <gitster@pobox•com>
To: Duy Nguyen <pclouds@gmail•com>
Cc: git@vger•kernel.org
Subject: Re: [PATCH v2 3/6] match_basename: use strncmp instead of strcmp
Date: Tue, 12 Mar 2013 13:59:40 -0700 [thread overview]
Message-ID: <7v7glc72rn.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <CACsJy8A_4SqLu5L6P0PJ78Lwy12fjL7T2p-KbVEVLJmKNqhyRw@mail.gmail.com> (Duy Nguyen's message of "Sun, 10 Mar 2013 17:38:37 +0700")
Duy Nguyen <pclouds@gmail•com> writes:
> glibc's C strncmp version does 4-byte comparison at a time when n >=4,
> then fall back to 1-byte for the rest. I don't know if it's faster
> than a plain always 1-byte comparison though. There's also the hand
> written assembly version that compares n from 1..16, not exactly sure
> how this version works yet.
It sounds to me more like "a very popular implementation of
strcmp/strncmp pair found to have more optimized strncmp than
strcmp". While that may be a good reason to justify this patch,
I do not think it justifies this:
>> strncmp is provided length information which could be taken advantage
>> by the underlying implementation.
After all, strcmp() could also be optimized to fetch word-at-a-time
while being careful about not overstepping the page boundary.
next prev parent reply other threads:[~2013-03-12 21:00 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-09 4:09 [PATCH 0/3] Trivial (and small) exclude optimizations Nguyễn Thái Ngọc Duy
2013-03-09 4:09 ` [PATCH 1/3] match_pathname: avoid calling strncmp if baselen is 0 Nguyễn Thái Ngọc Duy
2013-03-09 9:06 ` Antoine Pelisse
2013-03-09 4:09 ` [PATCH 2/3] dir.c: inline convenient *_icase helpers Nguyễn Thái Ngọc Duy
2013-03-09 4:09 ` [PATCH 3/3] match_basename: use strncmp instead of strcmp Nguyễn Thái Ngọc Duy
2013-03-09 7:50 ` Junio C Hamano
2013-03-09 8:47 ` Fredrik Gustafsson
2013-03-09 9:58 ` Duy Nguyen
2013-03-10 6:14 ` [PATCH v2 0/6] Exclude optimizations Nguyễn Thái Ngọc Duy
2013-03-10 6:14 ` [PATCH v2 1/6] match_pathname: avoid calling strncmp if baselen is 0 Nguyễn Thái Ngọc Duy
2013-03-10 6:14 ` [PATCH v2 2/6] dir.c: inline convenient *_icase helpers Nguyễn Thái Ngọc Duy
2013-03-10 6:14 ` [PATCH v2 3/6] match_basename: use strncmp instead of strcmp Nguyễn Thái Ngọc Duy
2013-03-10 7:34 ` Junio C Hamano
2013-03-10 10:38 ` Duy Nguyen
2013-03-10 11:43 ` Antoine Pelisse
2013-03-10 11:54 ` Antoine Pelisse
2013-03-10 12:06 ` Duy Nguyen
2013-03-10 12:11 ` Antoine Pelisse
2013-03-10 12:14 ` Duy Nguyen
2013-03-12 20:59 ` Junio C Hamano [this message]
2013-03-13 1:11 ` Duy Nguyen
2013-03-10 6:14 ` [PATCH v2 4/6] match_{base,path}name: replace strncmp_icase with strnequal_icase Nguyễn Thái Ngọc Duy
2013-03-10 6:14 ` [PATCH v2 5/6] dir.c: pass pathname length to last_exclude_matching Nguyễn Thái Ngọc Duy
2013-03-10 6:14 ` [PATCH v2 6/6] exclude: filter patterns by directory level Nguyễn Thái Ngọc Duy
2013-03-10 8:20 ` Junio C Hamano
2013-03-10 10:18 ` Duy Nguyen
2013-03-10 10:58 ` Junio C Hamano
2013-03-10 11:14 ` Duy Nguyen
2013-03-11 15:11 ` [PATCH v2 0/6] Exclude optimizations Duy Nguyen
2013-03-12 13:04 ` [PATCH v3 00/13] " Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 01/13] dir.c: add MEASURE_EXCLUDE code for tracking exclude performance Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 02/13] match_pathname: avoid calling strncmp if baselen is 0 Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 03/13] dir.c: inline convenient *_icase helpers Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 04/13] match_basename: use strncmp instead of strcmp Nguyễn Thái Ngọc Duy
2013-03-12 17:40 ` Antoine Pelisse
2013-03-13 1:05 ` Duy Nguyen
2013-03-12 13:04 ` [PATCH v3 05/13] match_{base,path}name: replace strncmp_icase with memequal_icase Nguyễn Thái Ngọc Duy
2013-03-13 1:14 ` Duy Nguyen
2013-03-12 13:04 ` [PATCH v3 06/13] dir: pass pathname length to last_exclude_matching Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 07/13] exclude: avoid calling prep_exclude on entries of the same directory Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 08/13] exclude: record baselen in the pattern Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 09/13] exclude: filter out patterns not applicable to the current directory Nguyễn Thái Ngọc Duy
2013-03-12 23:13 ` Eric Sunshine
2013-03-12 13:04 ` [PATCH v3 10/13] read_directory: avoid invoking exclude machinery on tracked files Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 11/13] Preallocate hash tables when the number of inserts are known in advance Nguyễn Thái Ngọc Duy
2013-03-12 13:04 ` [PATCH v3 12/13] name-hash: allow to lookup a name with precalculated base hash Nguyễn Thái Ngọc Duy
2013-03-12 13:05 ` [PATCH v3 13/13] read_directory: calculate name hashes incrementally Nguyễn Thái Ngọc Duy
2013-03-14 13:05 ` [PATCH v3 00/13] Exclude optimizations Duy Nguyen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=7v7glc72rn.fsf@alter.siamese.dyndns.org \
--to=gitster@pobox$(echo .)com \
--cc=git@vger$(echo .)kernel.org \
--cc=pclouds@gmail$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox