From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: git@vger.kernel.org
Cc: "Junio C Hamano" <gitster@pobox.com>,
"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: [PATCH v2 2/2] perf: add test showing exponential growth in path globbing
Date: Wed, 10 May 2017 22:53:16 +0000 [thread overview]
Message-ID: <20170510225316.31680-3-avarab@gmail.com> (raw)
In-Reply-To: <20170510225316.31680-1-avarab@gmail.com>
Add a test showing that ls-files times grow exponentially in the face
of some pathological globs, whereas refglobs via for-each-ref don't in
practice suffer from the same issue.
As noted in the test description this is a test to see whether Git
suffers from the issue noted in an article Russ Cox posted today about
common bugs in various glob implementations:
https://research.swtch.com/glob
The pathological git-ls-files globbing is done by wildmatch() in
wildmatch.c. The for-each-ref codepath also uses wildmatch(), but will
always match against e.g. "refs/tags/aaa...", not "aaa.." as
git-ls-files will.
I'm unsure why the pathological case isn't triggered by for-each-ref,
but in any case, now we have a performance test for it.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
t/perf/p0100-globbing.sh | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 48 insertions(+)
create mode 100755 t/perf/p0100-globbing.sh
diff --git a/t/perf/p0100-globbing.sh b/t/perf/p0100-globbing.sh
new file mode 100755
index 0000000000..e98fd7ce4b
--- /dev/null
+++ b/t/perf/p0100-globbing.sh
@@ -0,0 +1,48 @@
+#!/bin/sh
+
+test_description="Tests pathalogical globbing performance
+
+Shows how Git's globbing performance performs when given the sort of
+pathalogical patterns described in at https://research.swtch.com/glob
+"
+
+. ./perf-lib.sh
+
+test_globs_big='10 25 50 75 100'
+test_globs_small='1 2 3 4 5 6'
+
+test_perf_fresh_repo
+
+test_expect_success 'setup' '
+ for i in $(test_seq 1 100)
+ do
+ printf "a" >>refname &&
+ for j in $(test_seq 1 $i)
+ do
+ printf "a*" >>refglob.$i
+ done &&
+ echo b >>refglob.$i
+ done &&
+ test_commit $(cat refname) &&
+ for i in $(test_seq 1 100)
+ do
+ echo git tag $(cat refname)-$i
+ done &&
+ test_commit hello
+'
+
+for i in $test_globs_big
+do
+ test_perf "refglob((a*)^nb) against tag a^100; n = $i" '
+ git for-each-ref "refs/tags/$(cat refglob.'$i')b"
+ '
+done
+
+for i in $test_globs_small
+do
+ test_perf "fileglob((a*)^nb) against file (a^100).t; n = $i" '
+ git ls-files "$(cat refglob.'$i')b"
+ '
+done
+
+test_done
--
2.11.0
next prev parent reply other threads:[~2017-05-10 22:53 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-10 22:53 [PATCH v2 0/2] perf: show that wildmatch() regressed for pathological cases in v2.0 Ævar Arnfjörð Bjarmason
2017-05-10 22:53 ` [PATCH v2 1/2] perf: add function to setup a fresh test repo Ævar Arnfjörð Bjarmason
2017-05-10 23:30 ` Jonathan Nieder
2017-05-11 0:00 ` Ævar Arnfjörð Bjarmason
2017-05-11 0:33 ` Junio C Hamano
2017-05-11 9:55 ` Junio C Hamano
2017-05-11 9:59 ` Ævar Arnfjörð Bjarmason
2017-05-10 22:53 ` Ævar Arnfjörð Bjarmason [this message]
2017-05-10 23:33 ` [PATCH v2 2/2] perf: add test showing exponential growth in path globbing Jonathan Nieder
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