Set the equivalent of -U0 when generating diffs for "git log -G". As
seen in diffgrep_consume() we ignore any lines that aren't the "+" and
"-" lines, so the rest of the output wasn't being used.
It turns out that we spent quite a bit of CPU just on this[1]:
Test HEAD~ HEAD
-----------------------------------------------------------------------------------------
4209.2: git log -G'a' <limit-rev>.. 0.60(0.54+0.06) 0.52(0.46+0.05) -13.3%
4209.8: git log -G'uncommon' <limit-rev>.. 0.61(0.54+0.07) 0.53(0.47+0.06) -13.1%
4209.14: git log -G'[þæö]' <limit-rev>.. 0.60(0.55+0.04) 0.56(0.48+0.04) -6.7%
4209.21: git log -i -G'a' <limit-rev>.. 0.63(0.56+0.03) 0.54(0.48+0.05) -14.3%
4209.27: git log -i -G'uncommon' <limit-rev>.. 0.61(0.55+0.05) 0.53(0.47+0.06) -13.1%
4209.33: git log -i -G'[þæö]' <limit-rev>.. 0.61(0.53+0.07) 0.53(0.47+0.05) -13.1%
I also experimented with setting diff.interHunkContext to 10, 100
etc. As noted above it's useless for -G to have non-"+" and non-"-"
lines for the matching itself, but there's going to be some sweet spot
where if we can be handed bigger hunks at a time our matching might be
faster.
But alas, the results of that were:
Test HEAD~2 HEAD~ HEAD
------------------------------------------------------------------------------------------------------------------
4209.2: git log -G'a' <limit-rev>.. 0.61(0.53+0.07) 0.51(0.46+0.05) -16.4% 0.51(0.46+0.05) -16.4%
4209.8: git log -G'uncommon' <limit-rev>.. 0.66(0.55+0.05) 0.53(0.48+0.04) -19.7% 0.52(0.49+0.03) -21.2%
4209.14: git log -G'[þæö]' <limit-rev>.. 0.63(0.54+0.06) 0.51(0.44+0.07) -19.0% 0.52(0.46+0.06) -17.5%
4209.21: git log -i -G'a' <limit-rev>.. 0.62(0.54+0.07) 0.51(0.46+0.04) -17.7% 0.53(0.45+0.07) -14.5%
4209.27: git log -i -G'uncommon' <limit-rev>.. 0.62(0.56+0.06) 0.53(0.48+0.05) -14.5% 0.53(0.46+0.07) -14.5%
4209.33: git log -i -G'[þæö]' <limit-rev>.. 0.63(0.57+0.03) 0.58(0.46+0.06) -7.9% 0.53(0.46+0.06) -15.9%
I.e. maybe it's faster in some cases, but probably slower in general.
Those results are going to be crappy because we're matching a line at
a time, as opposed to some version of /m matching across the whole
diff (if possible). So that approach might be worth revisiting in the
future.
1. GIT_SKIP_TESTS="p4209.[1379] p4209.15 p4209.2[028] p4209.34" GIT_PERF_EXTRA= GIT_PERF_REPO=~/g/git/ GIT_PERF_REPEAT_COUNT=5 GIT_PERF_MAKE_OPTS='-j8 USE_LIBPCRE=Y CFLAGS=-O3 LIBPCREDIR=/home/avar/g/pcre2/inst' ./run HEAD~ HEAD -- p4209-pickaxe.sh
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
diffcore-pickaxe.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index cb865c8b29..5161c81057 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -60,7 +60,7 @@ static int diff_grep(mmfile_t *one, mmfile_t *two,
memset(&xecfg, 0, sizeof(xecfg));
ecbdata.regexp = regexp;
ecbdata.hit = 0;
- xecfg.ctxlen = o->context;
+ xecfg.ctxlen = 0;
xecfg.interhunkctxlen = o->interhunkcontext;
if (xdi_diff_outf(one, two, discard_hunk_line, diffgrep_consume,
&ecbdata, &xpp, &xecfg))
--
2.30.0.284.gd98b1dd5eaa7
