On 11/04/14 23:22, Junio C Hamano wrote:
[...]
> [New Topics]
>
> * nd/index-pack-one-fd-per-thread (2014-04-09) 1 commit
> - index-pack: work around thread-unsafe pread()
>
> Enable threaded index-pack on platforms without thread-unsafe
> pread() emulation.
>
> Will merge to 'next' and keep it there for the remainder of the cycle.
The commit message for commit 512ebe5d ("index-pack: work around
thread-unsafe pread()", 25-03-2014) is a little misleading.
The pread() implementation is only thread-unsafe on older versions of
cygwin (anything prior to v1.7 - aka v1.5). Indeed, index-pack has been
threaded on cygwin (v1.7) since commit 103d530f ("Cygwin 1.7 has thread-
safe pread", 19-07-2013). (So, it was released in v1.8.4, I guess).
Since I upgraded my cygwin installation long ago (well about 9 months
ago), I can no longer test patches on cygwin v1.5. Also, since commit
a50dec22 ("Makefile: update defaults for modern Cygwin", 01-04-2010)
tells us that cygwin v1.5 is no longer being actively supported, it
may be difficult to find anyone who can do that testing. (v1.5 was
the last version supported on windows 95, 98 and ME, so maybe ... :)
Yesterday, I briefly compared the performance of the master and pu
branches (respectively with and without this patch) on cygwin.
(There seems to be little difference in the performance, as expected).
$ uname -a
CYGWIN_NT-5.1 toshiba 1.7.29(0.272/5/3) 2014-04-07 13:44 i686 Cygwin
First, on the master branch:
$ ./git version
git version 1.9.2.459.g68773ac
$ git log -1 --decorate --oneline
68773ac (HEAD, origin/master, origin/HEAD, master) Sync with 1.9.2
$ cd t
$ time ./t5302-pack-index.sh
ok 1 - setup
...
ok 31 - running index-pack in the object store
# passed all 31 test(s)
1..31
real 1m11.984s
user 1m24.986s
sys 0m41.521s
$
$ cd perf
$ ./p5302-pack-index.sh
warning: $GIT_PERF_LARGE_REPO is $GIT_BUILD_DIR.
warning: This will work, but may not be a sufficiently large repo
warning: for representative measurements.
ok 1 - repack
perf 2 - index-pack 0 threads: 1 2 3 ok
perf 3 - index-pack 1 thread : 1 2 3 ok
perf 4 - index-pack 2 threads: 1 2 3 ok
perf 5 - index-pack 4 threads: 1 2 3 ok
perf 6 - index-pack 8 threads: 1 2 3 ok
perf 7 - index-pack default number of threads: 1 2 3 ok
# passed all 7 test(s)
1..7
Can't locate Git.pm in @INC (@INC contains: /usr/lib/perl5/site_perl/5.14/i686-cygwin-threads-64int /usr/lib/perl5/site_perl/5.14 /usr/lib/perl5/vendor_perl/5.14/i686-cygwin-threads-64int /usr/lib/perl5/vendor_perl/5.14 /usr/lib/perl5/5.14/i686-cygwin-threads-64int /usr/lib/perl5/5.14 /usr/lib/perl5/site_perl/5.10 /usr/lib/perl5/vendor_perl/5.10 /usr/lib/perl5/site_perl/5.8 .) at ./aggregate.perl line 5.
BEGIN failed--compilation aborted at ./aggregate.perl line 5.
$ PERL5LIB=/home/ramsay/lib/perl5/site_perl/5.14 ./aggregate.perl ./p5302-pack-index.sh
Test this tree
----------------------------------------------------------------
5302.2: index-pack 0 threads 38.60(34.38+0.93)
5302.3: index-pack 1 thread 36.48(34.74+0.90)
5302.4: index-pack 2 threads 26.60(36.57+1.87)
5302.5: index-pack 4 threads 27.32(37.46+2.38)
5302.6: index-pack 8 threads 27.18(38.38+3.01)
5302.7: index-pack default number of threads 25.40(36.07+2.09)
$
NOTE: that t/perf/aggregate.perl can't locate Git.pm; I haven't investigated
that.
Now, on the pu branch:
$ ./git version
git version 1.9.2.667.ge5b74e1
$ git log -1 --decorate --oneline
e5b74e1 (HEAD, origin/pu, pu) Merge branch 'jc/graph-post-root-gap' into pu
$ cd t
$ time ./t5302-pack-index.sh
ok 1 - setup
...
ok 31 - running index-pack in the object store
# passed all 31 test(s)
1..31
real 1m8.063s
user 1m26.151s
sys 0m40.477s
$
$ cd perf
$ PERL5LIB=/home/ramsay/lib/perl5/site_perl/5.14 ./p5302-pack-index.sh
warning: $GIT_PERF_LARGE_REPO is $GIT_BUILD_DIR.
warning: This will work, but may not be a sufficiently large repo
warning: for representative measurements.
ok 1 - repack
perf 2 - index-pack 0 threads: 1 2 3 ok
perf 3 - index-pack 1 thread : 1 2 3 ok
perf 4 - index-pack 2 threads: 1 2 3 ok
perf 5 - index-pack 4 threads: 1 2 3 ok
perf 6 - index-pack 8 threads: 1 2 3 ok
perf 7 - index-pack default number of threads: 1 2 3 ok
# passed all 7 test(s)
1..7
Test this tree
----------------------------------------------------------------
5302.2: index-pack 0 threads 37.90(34.40+0.82)
5302.3: index-pack 1 thread 37.93(34.79+0.96)
5302.4: index-pack 2 threads 27.75(36.46+1.98)
5302.5: index-pack 4 threads 27.93(37.24+2.82)
5302.6: index-pack 8 threads 29.34(38.23+3.04)
5302.7: index-pack default number of threads 26.25(36.55+1.84)
$
HTH
ATB,
Ramsay Jones
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