When PERF_EXTRA is enabled, p5302 checks the performance of index-pack
with various numbers of threads. This can be useful for deciding what
the default should be (which is currently capped at 3 threads based on
the results of this script).
However, we only go up to 8 threads, and modern machines may have more.
Let's get the number of CPUs from test-tool, and test various numbers of
threads between one and that maximum.
Note that the current tests aren't all identical, as we have to set
GIT_FORCE_THREADS for the --threads=1 test (which measures the overhead
of starting a single worker thread versus the "0" case of using the main
thread). To keep the loop simple, we'll keep the "0" case out of it, and
set GIT_FORCE_THREADS=1 for all of the other cases (it's a noop for all
but the "1" case, since numbers higher than 1 would always need
threads).
Note also that we could skip running "test-tool" if PERF_EXTRA isn't
set. However, there's some small value in knowing the number of threads,
so that we can mark each test as skipped in the output.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The primary function of the perf suite is to detect regressions (or
improvements) between versions of Git. The only numbers we show a direct
comparison for are timings between the same test run on two different
versions.
However, it can sometimes be used to collect other information. For
instance, p5302 runs the same index-pack operation with different thread
counts. The output doesn't directly compare these, but anybody
interested in working on index-pack can manually compare the results.
For a normal regression run of the full perf-suite, though, this incurs
a significant cost to generate numbers nobody will actually look at;
about 25% of the total time of the test suite is spent in p5302. And the
low-thread-count runs are the most expensive part of it, since they're
(unsurprisingly) not using as many threads.
Let's skip these tests by default, but make it possible for people
working on index-pack to still run them by setting an environment
variable. Rather than make this specific to p5302, let's introduce a
generic mechanism. This makes it possible to run the full suite with
every possible test if somebody really wants to burn some CPU.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The p5302 script runs "index-pack --stdin" in each timing test. It does
two things to try to get good timings:
1. we do the repo creation in a separate (non-timed) setup test, so
that our timing is purely the index-pack run
2. we use a separate repo for each test; this is important because the
presence of existing objects in the repo influences the result
(because we'll end up doing collision checks against them)
But this forgets one thing: we generally run each timed test multiple
times to reduce the impact of noise. Which means that repeats of each
test after the first will be subject to the collision slowdown from
point 2, and we'll generally just end up taking the first time anyway.
Instead, let's create the repo in the test (effectively undoing point
1). That does add a constant amount of extra work to each iteration, but
it's quite small compared to the actual effects we're interested in
measuring.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Before 7176a314 (index-pack: complain when --stdin is used outside of a
repo) index-pack silently created a non-existing target directory; now
the command refuses to work unless it's used against a valid repository.
That causes p5302 to fail, which relies on the former behavior. Fix it
by setting up the destinations for its performance tests using git init.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.
The backquoted form is the traditional method for command
substitution, and is supported by POSIX. However, all but the
simplest uses become complicated quickly. In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.
The patch was generated by:
for _f in $(find . -name "*.sh")
do
sed -i 's@`\(.*\)`@$(\1)@g' ${_f}
done
and then carefully proof-read.
Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This puts delta resolving on each base on a separate thread, one base
cache per thread. Per-thread data is grouped in struct thread_local.
When running with nr_threads == 1, no pthreads calls are made. The
system essentially runs in non-thread mode.
An experiment on a Xeon 24 core machine with git.git shows that
performance does not increase proportional to the number of cores. So
by default, we use maximum 3 cores. Some numbers with --threads from 1
to 16:
1..4
real 0m8.003s 0m5.307s 0m4.321s 0m3.830s
user 0m7.720s 0m8.009s 0m8.133s 0m8.305s
sys 0m0.224s 0m0.372s 0m0.360s 0m0.360s
5..8
real 0m3.727s 0m3.604s 0m3.332s 0m3.369s
user 0m9.361s 0m9.817s 0m9.525s 0m9.769s
sys 0m0.584s 0m0.624s 0m0.540s 0m0.560s
9..12
real 0m3.036s 0m3.139s 0m3.177s 0m2.961s
user 0m8.977s 0m10.205s 0m9.737s 0m10.073s
sys 0m0.596s 0m0.680s 0m0.684s 0m0.680s
13..16
real 0m2.985s 0m2.894s 0m2.975s 0m2.971s
user 0m9.825s 0m10.573s 0m10.833s 0m11.361s
sys 0m0.788s 0m0.732s 0m0.904s 0m1.016s
On an Intel dual core and linux-2.6.git
1..4
real 2m37.789s 2m7.963s 2m0.920s 1m58.213s
user 2m28.415s 2m52.325s 2m50.176s 2m41.187s
sys 0m7.808s 0m11.181s 0m11.224s 0m10.731s
Thanks Ramsay Jones for troubleshooting and support on MinGW platform.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
