Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> 于2021年7月3日周六 下午10:18写道： > Most of the problem, although this may not entirely fix the performance > regression, is that you're either looking up everything twice now, or > taking a much more expensive path. > Yeah, In get_object(), oid_object_info_extended() is called twice when we want print object's contents. The original intention is to reduce the call of oid_object_info_extended() once when using --textconv. Should we make --textconv and --filters have the same logic? In this way, without using --textconv and --filters, we can call oid_object_info_extended() only once. > I think using gprof is probably much more handy here. See [1. I did a > `git rev-list --all >rla` and ran that piped into 'git cat-file --batch' > with/without your pathces. Results: > > $ gprof ./git-master ./gmon-master.out | head -n 10 > Flat profile: > > Each sample counts as 0.01 seconds. > % cumulative self self total > time seconds seconds calls ms/call ms/call name > 14.29 0.02 0.02 475186 0.00 0.00 nth_packed_object_offset > 14.29 0.04 0.02 237835 0.00 0.00 hash_to_hex_algop_r > 7.14 0.05 0.01 5220425 0.00 0.00 hashcmp_algop > 7.14 0.06 0.01 4757120 0.00 0.00 hex2chr > 7.14 0.07 0.01 1732023 0.00 0.00 find_entry_ptr > > And: > > $ gprof ./git-new ./gmon-new.out |head -n 10 > Flat profile: > > Each sample counts as 0.01 seconds. > % cumulative self self total > time seconds seconds calls ms/call ms/call name > 7.32 0.06 0.06 764570 0.00 0.00 lookup_object > 7.32 0.12 0.06 237835 0.00 0.00 parse_commit_date > 4.88 0.16 0.04 712779 0.00 0.00 nth_packed_object_offset > 3.66 0.19 0.03 964574 0.00 0.00 bsearch_hash > 3.66 0.22 0.03 237835 0.00 0.00 grab_sub_body_contents > It seems that lookup_object() took a lot of time with the patch of my version . > If you e.g. make lookup_object() simply die when it's called you'll see > that before we don't call it at all, after your patch it's our #1 > function. > > Before when we have the simplest case of writing out an object this is > our callstack: > > (gdb) bt > #0 batch_write (opt=0x7fffffffde50, data=0x555555ab9470, len=52) at builtin/cat-file.c:298 > #1 0x000055555558b160 in batch_object_write (obj_name=0x55555597cef0 "504fe6b39f7747be6427f28d9ca97decf5e6cecf", scratch=0x7fffffffd8c0, > opt=0x7fffffffde50, data=0x7fffffffd7f0) at builtin/cat-file.c:375 > #2 0x000055555558b36e in batch_one_object (obj_name=0x55555597cef0 "504fe6b39f7747be6427f28d9ca97decf5e6cecf", scratch=0x7fffffffd8c0, opt=0x7fffffffde50, > data=0x7fffffffd7f0) at builtin/cat-file.c:431 > #3 0x000055555558b8ed in batch_objects (opt=0x7fffffffde50) at builtin/cat-file.c:588 > #4 0x000055555558c0d3 in cmd_cat_file (argc=0, argv=0x7fffffffe1e0, prefix=0x0) at builtin/cat-file.c:716 > #5 0x0000555555573adb in run_builtin (p=0x555555941870 <commands+240>, argc=2, argv=0x7fffffffe1e0) at git.c:461 > #6 0x0000555555573f00 in handle_builtin (argc=2, argv=0x7fffffffe1e0) at git.c:714 > #7 0x0000555555574182 in run_argv (argcp=0x7fffffffe08c, argv=0x7fffffffe080) at git.c:781 > #8 0x000055555557460f in cmd_main (argc=2, argv=0x7fffffffe1e0) at git.c:912 > #9 0x000055555565b508 in main (argc=3, argv=0x7fffffffe1d8) at common-main.c:52 > > After (well, here we're not even to writing it, just looking it up), the > BUG() is my addition: > > (gdb) bt > #0 BUG_fl (file=0x5555558ade71 "object.c", line=91, fmt=0x5555558ade6e "yo") at usage.c:290 > #1 0x00005555557441ca in lookup_object (r=0x5555559755c0 <the_repo>, oid=0x555555975160 <oi>) at object.c:91 > #2 0x000055555569dfc8 in lookup_commit (r=0x5555559755c0 <the_repo>, oid=0x555555975160 <oi>) at commit.c:62 > #3 0x00005555557445f5 in parse_object_buffer (r=0x5555559755c0 <the_repo>, oid=0x555555975160 <oi>, type=OBJ_COMMIT, size=342, buffer=0x555555ab48e0, > eaten_p=0x7fffffffd36c) at object.c:215 > #4 0x0000555555785094 in get_object (ref=0x7fffffffd6b0, deref=0, obj=0x7fffffffd520, oi=0x555555975160 <oi>, err=0x7fffffffd860) at ref-filter.c:1803 > #5 0x0000555555785c99 in populate_value (ref=0x7fffffffd6b0, err=0x7fffffffd860) at ref-filter.c:2030 > #6 0x0000555555785d7b in get_ref_atom_value (ref=0x7fffffffd6b0, atom=0, v=0x7fffffffd628, err=0x7fffffffd860) at ref-filter.c:2064 > #7 0x000055555578742f in format_ref_array_item (info=0x7fffffffd6b0, format=0x7fffffffde30, final_buf=0x7fffffffd880, error_buf=0x7fffffffd860) > at ref-filter.c:2659 > #8 0x000055555558ab1c in batch_object_write (obj_name=0x55555597e3f0 "504fe6b39f7747be6427f28d9ca97decf5e6cecf", scratch=0x7fffffffd880, > err=0x7fffffffd860, opt=0x7fffffffde10, data=0x7fffffffd800) at builtin/cat-file.c:225 > #9 0x000055555558ade5 in batch_one_object (obj_name=0x55555597e3f0 "504fe6b39f7747be6427f28d9ca97decf5e6cecf", scratch=0x7fffffffd880, err=0x7fffffffd860, > opt=0x7fffffffde10, data=0x7fffffffd800) at builtin/cat-file.c:298 > #10 0x000055555558b394 in batch_objects (batch=0x7fffffffde10, options=0x7fffffffd900) at builtin/cat-file.c:458 > #11 0x000055555558bbd5 in cmd_cat_file (argc=0, argv=0x7fffffffe1d0, prefix=0x0) at builtin/cat-file.c:585 > #12 0x0000555555573adb in run_builtin (p=0x555555942850 <commands+240>, argc=2, argv=0x7fffffffe1d0) at git.c:461 > #13 0x0000555555573f00 in handle_builtin (argc=2, argv=0x7fffffffe1d0) at git.c:714 > #14 0x0000555555574182 in run_argv (argcp=0x7fffffffe07c, argv=0x7fffffffe070) at git.c:781 > #15 0x000055555557460f in cmd_main (argc=2, argv=0x7fffffffe1d0) at git.c:912 > #16 0x000055555565afc1 in main (argc=3, argv=0x7fffffffe1c8) at common-main.c:52 > It seems that the call stack is very deep after using my version. > I.e. before in batch_object_write() we could use a cheap path of doing > oid_object_info_extended() and directly emitting the content. With your > version we're all the way down to parse_object_buffer(). Meaning that > we're going to be creating a "struct commit" or whatever if we're > looking at a commit, just to print out the raw contents. > I agree that the logic in ref-filter is too complicated in order to be able to print the structured object data. > I think the best next step here is to add a t/perf/t1006-cat-file.sh > test to stress these various cases, i.e. a plain --batch without a > format, with format, with --batch-all-objects etc. Try to then run that > on each of your commits against the preceding one and see if/when you > have regressions. > Make sence. > Aside from any double-lookups etc, the problem is also that you're > trying to handle a really general case (e.g. with textconv) in a Well, "--textconv" is a common situation? Here I may not be sure which scenarios where the upper application calls "git cat-file --batch" are the most common. > codepath that needs to be really fast. If anything we should be > inserting some more more optimization shortcuts for common cases into > it. E.g. I was able to trivially speed up 'cat-file --batch-check' on > "master" by hardcoding a path for our default format (patch at the end > of this mail): > > # passed all 2 test(s) > 1..2 > Test origin/master HEAD > ------------------------------------------------------------------------- > 1006.2: cat-file --batch-check 0.60(0.37+0.23) 0.35(0.33+0.02) -41.7% > > Anything that needs to handle general format patching is going to be > slower. I think /some/ performance regression if we're using something > that's not just the current light strbuf_expand() probably can't be > avoided, but we could/should try to make up the difference at least for > the common case of --batch or --batch-check without --textconv and > perhaps hardcode (and document that it's faster) a path for the default > formats). > Yeah, Like the hardcode in your patch may be a solution to the performance degradation. This will indeed help those upper-level applications that use the common case. > 1. https://sourceware.org/binutils/docs/gprof/Output.html > > diff --git a/builtin/cat-file.c b/builtin/cat-file.c > index 5ebf13359e8..775b7dd1b01 100644 > --- a/builtin/cat-file.c > +++ b/builtin/cat-file.c > @@ -360,6 +360,11 @@ static void batch_object_write(const char *obj_name, > struct batch_options *opt, > struct expand_data *data) > { > + int default_format = !strcmp(opt->format, "%(objectname) %(objecttype) %(objectsize)"); > + struct strbuf type_name = STRBUF_INIT; > + if (default_format) > + data->info.type_name = &type_name; > + > if (!data->skip_object_info && > oid_object_info_extended(the_repository, &data->oid, &data->info, > OBJECT_INFO_LOOKUP_REPLACE) < 0) { > @@ -369,14 +374,20 @@ static void batch_object_write(const char *obj_name, > return; > } > > - strbuf_reset(scratch); > - strbuf_expand(scratch, opt->format, expand_format, data); > - strbuf_addch(scratch, '\n'); > - batch_write(opt, scratch->buf, scratch->len); > - > - if (opt->print_contents) { > - print_object_or_die(opt, data); > - batch_write(opt, "\n", 1); > + if (default_format && !opt->print_contents) { > + fprintf(stdout, "%s %s %"PRIuMAX"\n", oid_to_hex(&data->oid), > + data->info.type_name->buf, > + (uintmax_t)*data->info.sizep); > + } else { > + strbuf_reset(scratch); > + strbuf_expand(scratch, opt->format, expand_format, data); > + strbuf_addch(scratch, '\n'); > + batch_write(opt, scratch->buf, scratch->len); > + > + if (opt->print_contents) { > + print_object_or_die(opt, data); > + batch_write(opt, "\n", 1); > + } > } > } > > diff --git a/t/perf/p1006-cat-file.sh b/t/perf/p1006-cat-file.sh > new file mode 100755 > index 00000000000..a295d334715 > --- /dev/null > +++ b/t/perf/p1006-cat-file.sh > @@ -0,0 +1,16 @@ > +#!/bin/sh > + > +test_description='Basic sort performance tests' > +. ./perf-lib.sh > + > +test_perf_default_repo > + > +test_expect_success 'setup' ' > + git rev-list --all >rla > +' > + > +test_perf 'cat-file --batch-check' ' > + git cat-file --batch-check <rla > +' > + > +test_done Thanks. -- ZheNing Hu
