p5302: count up to online-cpus for thread tests

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>

diff --git a/t/perf/p5302-pack-index.sh b/t/perf/p5302-pack-index.sh
index 23011ab739c7cfae3b9f29549b6d2a3fa17f3b49..228593d9ad6b3a5c9a0b45eb5814a3a8746d42bc 100755 (executable)
--- 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 PERF_EXTRA 'index-pack 0 threads' '
-       rm -rf repo.git &&
-       git init --bare repo.git &&
-       GIT_DIR=repo.git 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 PERF_EXTRA '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
-'
-
-test_perf PERF_EXTRA 'index-pack 2 threads' '
-       rm -rf repo.git &&
-       git init --bare repo.git &&
-       GIT_DIR=repo.git git index-pack --threads=2 --stdin < $PACK
-'
-
-test_perf PERF_EXTRA 'index-pack 4 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=4 --stdin < $PACK
+       GIT_DIR=repo.git git index-pack --threads=1 --stdin < $PACK
 '
 
-test_perf PERF_EXTRA '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 &&