Date: Thu, 29 Jul 2004 15:41:03 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Scott Long <scottl@freebsd.org> Cc: cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/alpha/alpha pmap.c src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c src/sys/vm vm_page.c Message-ID: <Pine.NEB.3.96L.1040729154004.46374J-100000@fledge.watson.org> In-Reply-To: <20040729131040.F32601@pooker.samsco.org>
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On Thu, 29 Jul 2004, Scott Long wrote: > > - Enable recursion on the page queues lock. This allows calls to > > vm_page_alloc(VM_ALLOC_NORMAL) and UMA's obj_alloc() with the page > > queues lock held. Such calls are made to allocate page table pages > > and pv entries. > > My understanding is that recursive mutexes are quite expensive. Is > recursion a common occurrance now, and is there a good way to > profile/measure these paths? No opinion on the change itself, but just to clarify this wording a little for those reading who don't follow the locking work blow-by-blow: flagging a mutex as recursive itself is not expensive, but the act of recursing the mutex is expensive. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Principal Research Scientist, McAfee Research
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