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From: Jeff King <peff@peff.net>
To: git@vger.kernel.org
Subject: [PATCH 2/3] p5302: count up to online-cpus for thread tests
Date: Fri, 21 Aug 2020 13:54:51 -0400	[thread overview]
Message-ID: <20200821175451.GB3263141@coredump.intra.peff.net> (raw)
In-Reply-To: <20200821175153.GA3263018@coredump.intra.peff.net>

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>
---
 t/perf/p5302-pack-index.sh | 47 +++++++++++++++++++-------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/t/perf/p5302-pack-index.sh b/t/perf/p5302-pack-index.sh
index 23011ab739..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 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 &&
-- 
2.28.0.694.g07780f7063


  parent reply	other threads:[~2020-08-21 17:54 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 17:51 [PATCH 0/3] index-pack threading defaults Jeff King
2020-08-21 17:53 ` [PATCH 1/3] p5302: disable thread-count parameter tests by default Jeff King
2020-08-21 17:54 ` Jeff King [this message]
2020-08-21 17:58   ` [PATCH 2/3] p5302: count up to online-cpus for thread tests Jeff King
2020-08-21 17:58 ` [PATCH 3/3] index-pack: adjust default threading cap Jeff King
2020-08-21 18:08   ` Eric Sunshine
2020-08-21 18:41     ` Jeff King
2020-08-22  1:16   ` brian m. carlson
2020-08-24 17:37     ` Jeff King
2020-08-24 17:55       ` Eric Sunshine
2020-08-21 18:44 ` [PATCH 0/3] index-pack threading defaults Jeff King
2020-08-21 18:59   ` Junio C Hamano
2020-08-21 19:14     ` Jeff King

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