Re: [PATCH 3/2] Avoid unnecessary strlen() calls

On Sun, 18 Mar 2007, Junio C Hamano wrote:

That's an interesting test-case (and I get 53 seconds, nyaah, nyaah ;)

However, it's almost totally *not* about object access any more with my patches. All the top profiling hits are about generating the patches and assigning blame:

	samples  %        image name               app name                 symbol name
	470352   15.5813  git                      git                      xdl_hash_record
	298683    9.8944  git                      git                      cmp_suspect
	225156    7.4587  git                      git                      assign_blame
	221308    7.3312  libc-2.5.so              libc-2.5.so              memcpy
	177621    5.8840  libc-2.5.so              libc-2.5.so              memchr
	163571    5.4186  vmlinux                  vmlinux                  __copy_user_nocache
	129301    4.2833  git                      git                      xdl_prepare_ctx
	99009     3.2799  libc-2.5.so              libc-2.5.so              _int_malloc
	83899     2.7793  git                      git                      xdiff_outf
	80588     2.6696  libz.so.1.2.3            libz.so.1.2.3            (no symbols)
	..

so as you can see, libz is down in the 2.5% range, and strlen and the tree accessor functions are totally un the noise.

So it looks like it *used* to be somewhat of a problem (the object access itself must have been about 10 seconds, since that got shaved off the time), but realistically, if you want to speed up "git blame", we can totally ignore the git object data structures, an dconcentrate on xdiff and on blame itself (cmp_suspect and assign_blame probably have some nasty O(n^2) behaviour or something like that, that could hopefully be fixed fairly easily. The xdl hashing is a different thing, and I don't think it's necessarily easy to fix that one..)

			Linus