@matheusbsbs / matheus-bagliano / commits / 018b9deba5

pretty: lazy-load commit data when expanding user-format

When we expand a user-format, we try to avoid work that isn't necessary for the output. For instance, we don't bother parsing the commit header until we know we need the author, subject, etc. But we do always load the commit object's contents from disk, even if the format doesn't require it (e.g., just "%H"). Traditionally this didn't matter much, because we'd have loaded it as part of the traversal anyway, and we'd typically have those bytes attached to the commit struct (or these days, cached in a commit-slab). But when we have a commit-graph, we might easily get to the point of pretty-printing a commit without ever having looked at the actual object contents. We should push off that load (and reencoding) until we're certain that it's needed. I think the results of p4205 show the advantage pretty clearly (we serve parent and tree oids out of the commit struct itself, so they benefit as well): # using git.git as the test repo Test HEAD^ HEAD ---------------------------------------------------------------------- 4205.1: log with %H 0.40(0.39+0.01) 0.03(0.02+0.01) -92.5% 4205.2: log with %h 0.45(0.44+0.01) 0.09(0.09+0.00) -80.0% 4205.3: log with %T 0.40(0.39+0.00) 0.04(0.04+0.00) -90.0% 4205.4: log with %t 0.46(0.46+0.00) 0.09(0.08+0.01) -80.4% 4205.5: log with %P 0.39(0.39+0.00) 0.03(0.03+0.00) -92.3% 4205.6: log with %p 0.46(0.46+0.00) 0.10(0.09+0.00) -78.3% 4205.7: log with %h-%h-%h 0.52(0.51+0.01) 0.15(0.14+0.00) -71.2% 4205.8: log with %an-%ae-%s 0.42(0.41+0.00) 0.42(0.41+0.01) +0.0% # using linux.git as the test repo Test HEAD^ HEAD ---------------------------------------------------------------------- 4205.1: log with %H 7.12(6.97+0.14) 0.76(0.65+0.11) -89.3% 4205.2: log with %h 7.35(7.19+0.16) 1.30(1.19+0.11) -82.3% 4205.3: log with %T 7.58(7.42+0.15) 1.02(0.94+0.08) -86.5% 4205.4: log with %t 8.05(7.89+0.15) 1.55(1.41+0.13) -80.7% 4205.5: log with %P 7.12(7.01+0.10) 0.76(0.69+0.07) -89.3% 4205.6: log with %p 7.38(7.27+0.10) 1.32(1.20+0.12) -82.1% 4205.7: log with %h-%h-%h 7.81(7.67+0.13) 1.79(1.67+0.12) -77.1% 4205.8: log with %an-%ae-%s 7.90(7.74+0.15) 7.81(7.66+0.15) -1.1% I added the final test to show where we don't improve (the 1% there is just lucky noise), but also as a regression test to make sure we're not doing anything stupid like loading the commit multiple times when there are several placeholders that need it. Reported-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Jan 28, 2021 at 14:57 UTC 018b9deba5c4971f321f2158e3a6308f479bfee3

2 files changed +13 -12

pretty.c

+12 -11

@@ -783,6 +783,7 @@ enum trunc_type {

783 };

784

785 struct format_commit_context {

786 + struct repository *repository;

787 const struct commit *commit;

788 const struct pretty_print_context *pretty_ctx;

789 unsigned commit_header_parsed:1;

@@ -1373,10 +1374,13 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */

1374 return 2;

1375 }

1376

1376 -

1377 /* For the rest we have to parse the commit header. */

1378 - if (!c->commit_header_parsed)

1378 + if (!c->commit_header_parsed) {

1379 + msg = c->message =

1380 + repo_logmsg_reencode(c->repository, commit,

1381 + &c->commit_encoding, "UTF-8");

1382 parse_commit_header(c);

1383 + }

1384

1385 switch (placeholder[0]) {

1386 case 'a': /* author ... */

@@ -1667,6 +1671,7 @@ void repo_format_commit_message(struct repository *r,

1671 const struct pretty_print_context *pretty_ctx)

1672 {

1673 struct format_commit_context context = {

1674 + .repository = r,

1675 .commit = commit,

1676 .pretty_ctx = pretty_ctx,

1677 .wrap_start = sb->len

@@ -1674,18 +1679,14 @@ void repo_format_commit_message(struct repository *r,

1679 const char *output_enc = pretty_ctx->output_encoding;

1680 const char *utf8 = "UTF-8";

1681

1677 - /*

1678 - * convert a commit message to UTF-8 first

1679 - * as far as 'format_commit_item' assumes it in UTF-8

1680 - */

1681 - context.message = repo_logmsg_reencode(r, commit,

1682 - &context.commit_encoding,

1683 - utf8);

1684 -

1682 strbuf_expand(sb, format, format_commit_item, &context);

1683 rewrap_message_tail(sb, &context, 0, 0, 0);

1684

1688 - /* then convert a commit message to an actual output encoding */

1685 + /*

1686 + * Convert output to an actual output encoding; note that

1687 + * format_commit_item() will always use UTF-8, so we don't

1688 + * have to bother if that's what the output wants.

1689 + */

1690 if (output_enc) {

1691 if (same_encoding(utf8, output_enc))

1692 output_enc = NULL;

t/perf/p4205-log-pretty-formats.sh

+1 -1

@@ -6,7 +6,7 @@ test_description='Tests the performance of various pretty format placeholders'

7 test_perf_default_repo

9 -for format in %H %h %T %t %P %p %h-%h-%h

9 +for format in %H %h %T %t %P %p %h-%h-%h %an-%ae-%s

10 do

11 test_perf "log with $format" "

12 git log --format=\"$format\" >/dev/null