On Tue, Apr 4, 2017 at 5:07 PM, Jeff Hostetler <git@xxxxxxxxxxxxxxxxx> wrote: > > 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 <avarab@xxxxxxxxx> >> --- >> >> 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. It's been enabled by default since 2.1.0 (299e29870b), or do you mean talk about disabling it, or "this is a perf option we have on by default"? I don't know the pros of disabling that, haven't used it myself & it's not clear from the docs. > For people with very large trees, talk about sparse-checkout. *nod* > And (on Windows) core.fscache. Or leave a place for > an addendum for Windows that we can fill in later. I have no core.fscache in my git.git, did you mean something else? > > >> >> >> 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[1]) 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[1]). >> + >> +- config: "status.showUntrackedFiles=no" (see >> + linkgit:git-config[1]). 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[1]) 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[1] & >> + linkgit:git-grep[1]). 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[1]). 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[1] suite >> >