Date: Tue, 3 Apr 2001 17:20:42 -0700 (PDT) From: Matt Dillon <dillon@earth.backplane.com> To: Bosko Milekic <bmilekic@technokratis.com> Cc: Garrett Rooney <rooneg@electricjellyfish.net>, Alfred Perlstein <alfred@FreeBSD.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/sys mbuf.h src/sys/kern uipc_mbuf.c Message-ID: <200104040020.f340Kgi74269@earth.backplane.com> References: <200104030315.f333FCX69312@freefall.freebsd.org> <20010403140457.B2952@electricjellyfish.net> <200104031813.f33ID4b58965@earth.backplane.com> <20010403194004.A15434@technokratis.com>
next in thread | previous in thread | raw e-mail | index | archive | help
: The reason for the removal isn't related to pollution of system
:structures per se (i.e. bloat). There were really only three locks, one
:for each free list.
: The removal is, the way I see it, a slight pessimization in some
:cases at this moment, due to the increase of contention again, in some cases.
:...
Ok... hmm. Since compare-exchange support is mandatory now, why not
simply use it to implement per-cpu free lists for mbufs that does not
require any (mutex) locking at all? This solves the contention problem
and the interrupt problem.
e.g. (pseudo code)
allocMBufHeader()
{
struct mbuf *mb;
while ((mb = PerCpuMBufHeaderBase) != NULL) {
if (cmpexchangeptr(&PerCpuMBufHeaderBase, mb, mb->mb_Next) == mb)
break;
}
if (mb == NULL) {
slow version
}
return(mb);
}
freeMBufHeader(mb)
{
for (;;) {
mb->mb_Next = PerCpuMBufHeaderBase;
if (cmpexchangeptr(&PerCpuMBufHeaderBase, mb->mb_Next, mb) == mb->mb_Next)
break;
}
}
-Matt
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe cvs-all" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200104040020.f340Kgi74269>