Messages in this thread | | | Date | Thu, 22 Sep 2005 15:05:50 +0200 | From | Eric Dumazet <> | Subject | Re: [PATCH 2/3] netfilter : 3 patches to boost ip_tables performance |
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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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