Re: Git and GCC

From: David Miller <davem@davemloft.net>
Date: Fri, 07 Dec 2007 04:53:29 -0800 (PST)

While doing the initial object counting, most of the time is spent in lookup_object(), memcmp() (via hashcmp()), and inflate(). I tried to see if I could do some tricks on sparc with the hashcmp() but the sha1 pointers are very often not even 4 byte aligned.

I suspect lookup_object() could be improved if it didn't use a hash table without chaining, but I can see why 'struct object' size is a concern and thus why things are done the way they are.

samples  %        app name                 symbol name
504      13.7517  libc-2.6.1.so            memcmp
386      10.5321  libz.so.1.2.3.3          inflate
288       7.8581  git                      lookup_object
248       6.7667  libz.so.1.2.3.3          inflate_fast
201       5.4843  libz.so.1.2.3.3          inflate_table
175       4.7749  git                      decode_tree_entry
 ...

Deltifying is %94 consumed by create_delta(), the rest is completely in the noise.

samples  %        app name                 symbol name
10581    94.8373  git                      create_delta
181       1.6223  git                      create_delta_index
72        0.6453  git                      prepare_pack
55        0.4930  libc-2.6.1.so            loop
34        0.3047  libz.so.1.2.3.3          inflate_fast
33        0.2958  libc-2.6.1.so            _int_malloc
22        0.1972  libshadow.so             shadowUpdatePacked
21        0.1882  libc-2.6.1.so            _int_free
19        0.1703  libc-2.6.1.so            malloc
 ...