diff options
| -rw-r--r-- | builtin/index-pack.c | 19 | ||||
| -rw-r--r-- | t/perf/README | 9 | ||||
| -rwxr-xr-x | t/perf/p5302-pack-index.sh | 47 | ||||
| -rw-r--r-- | t/perf/perf-lib.sh | 2 |
4 files changed, 51 insertions, 26 deletions
diff --git a/builtin/index-pack.c b/builtin/index-pack.c index f865666db9..9721bf1ffe 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -1798,9 +1798,22 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix) if (HAVE_THREADS && !nr_threads) { nr_threads = online_cpus(); - /* An experiment showed that more threads does not mean faster */ - if (nr_threads > 3) - nr_threads = 3; + /* + * Experiments show that going above 20 threads doesn't help, + * no matter how many cores you have. Below that, we tend to + * max at half the number of online_cpus(), presumably because + * half of those are hyperthreads rather than full cores. We'll + * never reduce the level below "3", though, to match a + * historical value that nobody complained about. + */ + if (nr_threads < 4) + ; /* too few cores to consider capping */ + else if (nr_threads < 6) + nr_threads = 3; /* historic cap */ + else if (nr_threads < 40) + nr_threads /= 2; + else + nr_threads = 20; /* hard cap */ } curr_pack = open_pack_file(pack_name); diff --git a/t/perf/README b/t/perf/README index c7b70e2d28..bd649afa97 100644 --- a/t/perf/README +++ b/t/perf/README @@ -84,6 +84,15 @@ You can set the following variables (also in your config.mak): probably be about linux.git size for optimal results. Both default to the git.git you are running from. + GIT_PERF_EXTRA + Boolean to enable additional tests. Most test scripts are + written to detect regressions between two versions of Git, and + the output will compare timings for individual tests between + those versions. Some scripts have additional tests which are not + run by default, that show patterns within a single version of + Git (e.g., performance of index-pack as the number of threads + changes). These can be enabled with GIT_PERF_EXTRA. + You can also pass the options taken by ordinary git tests; the most useful one is: diff --git a/t/perf/p5302-pack-index.sh b/t/perf/p5302-pack-index.sh index a9b3e112d9..228593d9ad 100755 --- a/t/perf/p5302-pack-index.sh +++ b/t/perf/p5302-pack-index.sh @@ -13,35 +13,36 @@ test_expect_success 'repack' ' export PACK ' -test_perf 'index-pack 0 threads' ' - rm -rf repo.git && - git init --bare repo.git && - GIT_DIR=repo.git git index-pack --threads=1 --stdin < $PACK -' - -test_perf 'index-pack 1 thread ' ' - rm -rf repo.git && - git init --bare repo.git && - GIT_DIR=repo.git GIT_FORCE_THREADS=1 git index-pack --threads=1 --stdin < $PACK +# Rather than counting up and doubling each time, count down from the endpoint, +# halving each time. That ensures that our final test uses as many threads as +# CPUs, even if it isn't a power of 2. +test_expect_success 'set up thread-counting tests' ' + t=$(test-tool online-cpus) && + threads= && + while test $t -gt 0 + do + threads="$t $threads" + t=$((t / 2)) + done ' -test_perf 'index-pack 2 threads' ' +test_perf PERF_EXTRA 'index-pack 0 threads' ' rm -rf repo.git && git init --bare repo.git && - GIT_DIR=repo.git git index-pack --threads=2 --stdin < $PACK -' - -test_perf 'index-pack 4 threads' ' - rm -rf repo.git && - git init --bare repo.git && - GIT_DIR=repo.git git index-pack --threads=4 --stdin < $PACK + GIT_DIR=repo.git git index-pack --threads=1 --stdin < $PACK ' -test_perf 'index-pack 8 threads' ' - rm -rf repo.git && - git init --bare repo.git && - GIT_DIR=repo.git git index-pack --threads=8 --stdin < $PACK -' +for t in $threads +do + THREADS=$t + export THREADS + test_perf PERF_EXTRA "index-pack $t threads" ' + rm -rf repo.git && + git init --bare repo.git && + GIT_DIR=repo.git GIT_FORCE_THREADS=1 \ + git index-pack --threads=$THREADS --stdin <$PACK + ' +done test_perf 'index-pack default number of threads' ' rm -rf repo.git && diff --git a/t/perf/perf-lib.sh b/t/perf/perf-lib.sh index 13e389367a..821581a885 100644 --- a/t/perf/perf-lib.sh +++ b/t/perf/perf-lib.sh @@ -245,3 +245,5 @@ test_at_end_hook_ () { test_export () { export "$@" } + +test_lazy_prereq PERF_EXTRA 'test_bool_env GIT_PERF_EXTRA false' |