Harald Welte a écrit :
On Wed, Sep 21, 2005 at 11:32:24PM +0200, Eric Dumazet wrote:
Patch 2/3 (please apply after Patch 1/3)
2) Loop unrolling
First of all, thanks for your performance analysis and patches. I'm
very inclined of merging them.
It seems that with current compilers and CFLAGS, the code from
ip_packet_match() is very bad, using lot of mispredicted conditional branches I made some patches
and generated code on i386 and x86_64
is much better.
This only describes your "compare_if_lstrings()" changes, and I'm happy
to merge them.
However, you also removed the use of the FWINV macro and replaced it by
explicit code (including the bool1/bool2 variables, which are not really
named intuitively). Why was this neccessary?
It was necessary to get the best code with gcc-3.4.4 on i386 and gcc-4.0.1 on
x86_64
For example :
bool1 = FWINV(ret != 0, IPT_INV_VIA_OUT);
if (bool1) {
gives a better code than :
if (FWINV(ret != 0, IPT_INV_VIA_OUT)) {
(one less conditional branch)
Dont ask me why, it is shocking but true :(
Eric
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