On Wed, Oct 3, 2012 at 11:20 PM, Jeff King <peff@xxxxxxxx> wrote:
Thanks for all that info, it's really useful.
>> * A co-worker who was working on this today tried it on 1.7.12 and
>> claimed that it had the same performance characteristics.
>
> That's surprising to me. Can you try to verify those numbers?
I think he was wrong, I tested this on git.git by first creating a lot
of tags:
parallel --eta "git tag -a -m"{}" test-again-{}" ::: $(git rev-list HEAD)
Then doing:
git pack-refs --all
git repack -A -d
And compiled with -g -O3 I get around 1.55 runs/s of git-upload-pack
on 1.7.8 and 2.59/s on the master branch.
>> * I tried to profile it under gcc -pg && echo -n | ./git-upload-pack
>> <repo> but it doesn't produce a profile like that, presumably
>> because the process exits unsuccessfully.
>
> If it's a recent version of Linux, you'll get much nicer results with
> perf. Here's what my 400K-ref case looks like:
>
> $ time echo 0000 | perf record git-upload-pack . >/dev/null
> real 0m0.808s
> user 0m0.660s
> sys 0m0.136s
>
> $ perf report | grep -v ^# | head
> 11.40% git-upload-pack libc-2.13.so [.] vfprintf
> 9.70% git-upload-pack git-upload-pack [.] find_pack_entry_one
> 7.64% git-upload-pack git-upload-pack [.] check_refname_format
> 6.81% git-upload-pack libc-2.13.so [.] __memcmp_sse4_1
> 5.79% git-upload-pack libc-2.13.so [.] getenv
> 4.20% git-upload-pack libc-2.13.so [.] __strlen_sse42
> 3.72% git-upload-pack git-upload-pack [.] ref_entry_cmp_sslice
> 3.15% git-upload-pack git-upload-pack [.] read_packed_refs
> 2.65% git-upload-pack git-upload-pack [.] sha1_to_hex
> 2.44% git-upload-pack libc-2.13.so [.] _IO_default_xsputn
FWIW here are my results on the above pathological git.git
$ uname -r; perf --version; echo 0000 | perf record
./git-upload-pack .>/dev/null; perf report | grep -v ^# | head
3.2.0-2-amd64
perf version 3.2.17
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.026 MB perf.data (~1131 samples) ]
29.08% git-upload-pack libz.so.1.2.7 [.] inflate
17.99% git-upload-pack libz.so.1.2.7 [.] 0xaec1
6.21% git-upload-pack libc-2.13.so [.] 0x117503
5.69% git-upload-pack libcrypto.so.1.0.0 [.] 0x82c3d
4.87% git-upload-pack git-upload-pack [.] find_pack_entry_one
3.18% git-upload-pack ld-2.13.so [.] 0x886e
2.96% git-upload-pack libc-2.13.so [.] vfprintf
2.83% git-upload-pack git-upload-pack [.] search_for_subdir
1.56% git-upload-pack [kernel.kallsyms] [k] do_raw_spin_lock
1.36% git-upload-pack libc-2.13.so [.] vsnprintf
I wonder why your report doesn't note any time in libz. This is on
Debian testing, maybe your OS uses different strip settings so it
doesn't show up?
$ ldd -r ./git-upload-pack
linux-vdso.so.1 => (0x00007fff621ff000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f768feee000)
libcrypto.so.1.0.0 =>
/usr/lib/x86_64-linux-gnu/libcrypto.so.1.0.0 (0x00007f768fb0a000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
(0x00007f768f8ed000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f768f566000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f768f362000)
/lib64/ld-linux-x86-64.so.2 (0x00007f7690117000
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