Date: Tue, 09 Nov 2004 10:36:18 -0800 From: Julian Elischer <julian@elischer.org> To: Stephan Uphoff <ups@tree.com> Cc: Robert Watson <rwatson@FreeBSD.org> Subject: Re: cvs commit: src/sys/i386/i386 pmap.c Message-ID: <41910E22.4070409@elischer.org> In-Reply-To: <1100024464.29384.30.camel@palm.tree.com> References: <Pine.NEB.3.96L.1041109103037.73102S-100000@fledge.watson.org> <4191062A.6090009@elischer.org> <1100024464.29384.30.camel@palm.tree.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Stephan Uphoff wrote: >On Tue, 2004-11-09 at 13:02, Julian Elischer wrote: > > >>Can you explain why a spin mutex is more expensive than a sleep mutex (I >>assume this is uncontested)? >> >> > >cli() and sti() used for the critical section are expensive. >( The spin mutex includes the critical section) > >I recall a USENIX paper about avoiding the cost of cli(),sti() by just >setting an in memory flag. The interrupt handler was modified to honor >the flag and delay interrupt processing until the flag was cleared. >This may have the potential to drastically decrease the cost of a spin >mutex if interrupts during critical regions are infrequent. > yes we USED to do that.. why do we no longer do this? > > Stephan > >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?41910E22.4070409>