From: Jeff Hostetler <firstname.lastname@example.org> To: "Ævar Arnfjörð Bjarmason" <email@example.com>, firstname.lastname@example.org Cc: Junio C Hamano <email@example.com>, Jeff King <firstname.lastname@example.org> Subject: Re: [PATCH/RFC] gitperformance: add new documentation about git performance tuning Date: Tue, 4 Apr 2017 11:07:38 -0400 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 4/3/2017 5:16 PM, Ævar Arnfjörð Bjarmason wrote: > Add a new manpage that gives an overview of how to tweak git's > performance. > > There's currently no good single resource for things a git site > administrator might want to look into to improve performance for his > site & his users. This unfinished documentation aims to be the first > thing someone might want to look at when investigating ways to improve > git performance. > > Signed-off-by: Ævar Arnfjörð Bjarmason <email@example.com> > --- > > I've been wanting to get something like this started for a while. It's > obviously woefully incomplete. Pointers about what to include would be > great & whether including something like this makes sense. > > Things I have on my TODO list: > > - Add a section discussing how refs impact performance, suggest > e.g. archiving old tags if possible, or at least run "git remote > prune origin" regularly on clients. > > - Discuss split index a bit, although I'm not very confident in > describing what its pros & cons are. > > - Should we be covering good practices for your repo going forward to > maintain good performance? E.g. don't have some huge tree all in > one directory (use subdirs), don't add binary (rather > un-delta-able) content if you can help it etc. > > - The new core.checksumIndex option being discussed on-list. Which > actually drove my to finally write this up (hrm, this sounds useful, > but unless I was watching the list I'd probably never see it...). You might also consider core.preloadIndex. For people with very large trees, talk about sparse-checkout. And (on Windows) core.fscache. Or leave a place for an addendum for Windows that we can fill in later. > > > Documentation/Makefile | 1 + > Documentation/gitperformance.txt | 107 +++++++++++++++++++++++++++++++++++++++ > 2 files changed, 108 insertions(+) > create mode 100644 Documentation/gitperformance.txt > > diff --git a/Documentation/Makefile b/Documentation/Makefile > index b5be2e2d3f..528aa22354 100644 > --- a/Documentation/Makefile > +++ b/Documentation/Makefile > @@ -23,6 +23,7 @@ MAN5_TXT += gitrepository-layout.txt > MAN5_TXT += gitweb.conf.txt > > MAN7_TXT += gitcli.txt > +MAN7_TXT += gitperformance.txt > MAN7_TXT += gitcore-tutorial.txt > MAN7_TXT += gitcredentials.txt > MAN7_TXT += gitcvs-migration.txt > diff --git a/Documentation/gitperformance.txt b/Documentation/gitperformance.txt > new file mode 100644 > index 0000000000..0548d1e721 > --- /dev/null > +++ b/Documentation/gitperformance.txt > @@ -0,0 +1,107 @@ > +giteveryday(7) > +============== > + > +NAME > +---- > +gitperformance - How to improve Git's performance > + > +SYNOPSIS > +-------- > + > +A guide to improving Git's performance beyond the defaults. > + > +DESCRIPTION > +----------- > + > +Git is mostly performant by default, but ships with various > +configuration options, command-line options, etc. that might improve > +performance, but for various reasons aren't on by default. > + > +This document provides a brief overview of these features. > + > +The reader should not assume that turning on all of these features > +will increase performance, depending on the repository, workload & > +use-case turning some of them on might severely harm performance. > + > +This document serves as a starting point for things to look into when > +it comes to improving performance, not as a checklist for things to > +enable or disable. > + > +Performance by topic > +-------------------- > + > +It can be hard to divide the performance features into topics, but > +most of them fall into various well-defined buckets. E.g. there are > +features that help with the performance of "git status", and couldn't > +possibly impact repositories without working copies, and then some > +that only impact the performance of cloning from a server, or help the > +server itself etc. > + > +git status > +~~~~~~~~~~ > + > +Running "git status" requires traversing the working tree & comparing > +it with the index. Several configuration options can help with its > +performance, with some trade-offs. > + > +- config: "core.untrackedCache=true" (see linkgit:git-config) can > + save on `stat(2)` calls by caching the mtime of filesystem > + directories, and if they didn't change avoid recursing into that > + directory to `stat(2)` every file in them. > ++ > +pros: Can drastically speed up "git status". > ++ > +cons: There's a speed hit for initially populating & maintaining the > +cache. Doesn't work on all filesystems (see `--test-untracked-cache` > +in linkgit:git-update-index). > + > +- config: "status.showUntrackedFiles=no" (see > + linkgit:git-config). Skips looking for files in the working tree > + git doesn't already know about. > ++ > +pros: Speeds up "git status" by making it do a lot less work. > ++ > +cons: If there's any new & untracked files anywhere in the working > +tree they won't be noticed by git. Makes it easy to accidentally miss > +files to "git add" before committing, or files which might impact the > +code in the working tree, but which git won't know exist. > + > +git grep > +~~~~~~~~ > + > +- config: "grep.patternType=perl" (see linkgit:git-config) will use > + the PCRE library when "git grep" is invoked by default. This can be > + faster than POSIX regular expressions in many cases. > ++ > +pros: Can, depending on the use-case, be faster than default "git grep". > ++ > +cons: Can also be slower, and in some edge cases produce different > +results. > + > +- config: "grep.threads=*" (see linkgit:git-config & > + linkgit:git-grep). Tunes the number of "git grep" worker threads. > ++ > +pros: Giving this a more optimal value might result in a faster grep. > ++ > +cons: It might not. > + > +Server options to help clients > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +These features can be enabled on git servers, they won't help the > +performance of the servers themselves, but will help clients that need > +to talk to those servers. > + > +- config: "repack.writeBitmaps=true" (see > + linkgit:git-config). Spend more time during repack to produce > + bitmap index, helps clients with "fetch" & "clone" performance. > ++ > +pros: Once enabled & run regularly as part of "git repack" speeds up > +"clone" and "fetch". > ++ > +cons: Takes extra time during repack, requires doing full > +non-incremental repacks with `-A` or `-a`. > + > +GIT > +--- > +Part of the linkgit:git suite >
next prev parent reply other threads:[~2017-04-04 15:07 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-04-03 21:16 Ævar Arnfjörð Bjarmason 2017-04-03 21:34 ` Eric Wong 2017-04-03 21:57 ` Ævar Arnfjörð Bjarmason 2017-04-03 22:39 ` Eric Wong 2017-04-04 21:12 ` Ævar Arnfjörð Bjarmason 2017-04-04 2:19 ` Jeff King 2017-04-04 15:07 ` Jeff Hostetler [this message] 2017-04-04 15:18 ` Ævar Arnfjörð Bjarmason 2017-04-04 18:25 ` Jeff Hostetler 2017-04-05 12:56 ` Duy Nguyen
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