Date: Sun, 24 Jun 2001 18:34:54 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Peter Wemm <peter@wemm.org> Cc: Bruce Evans <bde@zeta.org.au>, Mikhail Teterin <mi@aldan.algebra.com>, jlemon@FreeBSD.org, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: kernel size w/ optimized bzero() & patch set (was Re: Inline optimized bzero (was Re: cvs commit: src/sys/netinettcp_subr.c)) Message-ID: <200106250134.f5P1YsN01440@earth.backplane.com> References: <20010625060743.292F7380B@overcee.netplex.com.au>
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:Just think.. This new ``improved'' bzero code can now fill up all 4K of L1
:instruction cache on most of my systems, and most of my 8K L1 instruction
:cache on >= coppermine cpus. I'm impressed. Those microbenchmarks had
Huh? Peter, you obviously haven't been listening. I strongly recommend
that you review the last few postings I've made. The suggested bzero
code certainly does NOT in any way blow up the L1 cache, and I think
I'm pretty clear on that. I wouldn't be doing it if it did.
:better be damn good, because it may end up the only thing that the system
:will do well now since all this excessive inlining looks like it is blowing
:the L1 cache out the door.
:
:(I also apply the same complaint to the vm/* inlines).
:
:Cheers,
:-Peter
And you are just as wrong. The few functions inlined in vm/* are inlined
mainly because (A) they are called with constant arguments, which means
that the resulting code will typically take up no more space then the
call that would have been there in the first place, or (B) they do
something that only takes a small number of instructions anyway, or
(C) they are called so few times that inlining will produce higher
performance without eating the L1 cache any more then it would have
otherwise.
I constructed those inlines very carefully and ran assembly output to
make sure they worked the way they were supposed to. Period dot. If
you have a problem with it, produce some hard evidence and I will review
it.
-Matt
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