Re: [PATCH v2] Make git_dir a path relative to work_tree in setup_work_tree()
- From
Linus Torvalds <torvalds@linux-foundation.org>
- Date
- Jun 19, 2008, 19:34 UTC
- Message-ID
- <alpine.LFD.1.10.0806191206350.2907@woody.linux-foundation.org>
- In-Reply-To
- <7vod5xuvtj.fsf@gitster.siamese.dyndns.org>
On Thu, 19 Jun 2008, Junio C Hamano wrote:
> > Other than that, I think the change is Ok, but as a "performance tweak", > it should be backed by some numbers, please?
Daniel's patch didn't apply for me as-is, so I recreated it with some differences (appended), and here are the numbers from ten runs each.
There is some IO for me - probably due to more-or-less random flushing of the journal - so the variation is bigger than I'd like, but whatever:
Before: real 0m8.135s real 0m7.933s real 0m8.080s real 0m7.954s real 0m7.949s real 0m8.112s real 0m7.934s real 0m8.059s real 0m7.979s real 0m8.038s
After: real 0m7.685s real 0m7.968s real 0m7.703s real 0m7.850s real 0m7.995s real 0m7.817s real 0m7.963s real 0m7.955s real 0m7.848s real 0m7.969s
Now, going by "best of ten" (on the assumption that the longer numbers are all due to IO), I'm saying a 7.933s -> 7.685s reduction, and it does seem to be outside of the noise (ie the "after" case never broke 8s, while the "before" case did so half the time).
So looks like about 3% to me.
Doing it for a slightly smaller test-case (just the "arch" subdirectory) gets more stable numbers probably due to not filling the journal with metadata updates, so we have:
Before: real 0m1.633s real 0m1.633s real 0m1.633s real 0m1.632s real 0m1.632s real 0m1.630s real 0m1.634s real 0m1.631s real 0m1.632s real 0m1.632s
After: real 0m1.610s real 0m1.609s real 0m1.610s real 0m1.608s real 0m1.607s real 0m1.610s real 0m1.609s real 0m1.611s real 0m1.608s real 0m1.611s
where I'ld just take the averages and say 1.632 vs 1.610, which is just over 1% peformance improvement.
So it's not in the noise, but it's not as big as I initially thought and measured.
(That said, it obviously depends on how deep the working directory path is too, and whether it is behind NFS or something else that might need to cause more work to look up).
Modified/updated patch appended.
Linus
---- cache.h | 1 + path.c | 17 +++++++++++++++++ setup.c | 3 ++- 3 files changed, 20 insertions(+), 1 deletions(-)
diff --git a/cache.h b/cache.h index 01c8502..29aae0c 100644 --- a/cache.h +++ b/cache.h @@ -526,6 +526,7 @@ static inline int is_absolute_path(const char *path) } const char *make_absolute_path(const char *path); const char *make_nonrelative_path(const char *path); +const char *make_relative_path(const char *abs, const char *base); /* Read and unpack a sha1 file into memory, write memory to a sha1 file */ extern int sha1_object_info(const unsigned char *, unsigned long *); diff --git a/path.c b/path.c index 7a35a26..6e3df18 100644 --- a/path.c +++ b/path.c @@ -330,6 +330,23 @@ const char *make_nonrelative_path(const char *path) /* We allow "recursive" symbolic links. Only within reason, though. */ #define MAXDEPTH 5 +const char *make_relative_path(const char *abs, const char *base) +{ + static char buf[PATH_MAX + 1]; + int baselen; + if (!base) + return abs; + baselen = strlen(base); + if (prefixcmp(abs, base)) + return abs; + if (abs[baselen] == '/') + baselen++; + else if (base[baselen - 1] != '/') + return abs; + strcpy(buf, abs + baselen); + return buf; +} + const char *make_absolute_path(const char *path) { static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1]; diff --git a/setup.c b/setup.c index d630e37..3b111ea 100644 --- a/setup.c +++ b/setup.c @@ -292,9 +292,10 @@ void setup_work_tree(void) work_tree = get_git_work_tree(); git_dir = get_git_dir(); if (!is_absolute_path(git_dir)) - set_git_dir(make_absolute_path(git_dir)); + git_dir = make_absolute_path(git_dir); if (!work_tree || chdir(work_tree)) die("This operation must be run in a work tree"); + set_git_dir(make_relative_path(git_dir, work_tree)); initialized = 1; }