Date: Wed, 22 Jun 2011 09:48:02 -0400 From: John Baldwin <jhb@freebsd.org> To: Bruce Evans <brde@optusnet.com.au> Cc: Alan Cox <alc@freebsd.org>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, "Bjoern A. Zeeb" <bz@freebsd.org>, src-committers@freebsd.org Subject: Re: svn commit: r223307 - head/sys/vm Message-ID: <201106220948.02421.jhb@freebsd.org> In-Reply-To: <20110622063258.D2275@besplex.bde.org> References: <201106191913.p5JJDOqJ006272@svn.freebsd.org> <BBC34F79-FFA7-4A05-83B3-DE17E0AB14D0@FreeBSD.org> <20110622063258.D2275@besplex.bde.org>
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On Tuesday, June 21, 2011 4:58:10 pm Bruce Evans wrote: > On Tue, 21 Jun 2011, Bjoern A. Zeeb wrote: > > > On Jun 19, 2011, at 7:13 PM, Alan Cox wrote: > > > > Hi Alan, > > > >> Author: alc > >> Date: Sun Jun 19 19:13:24 2011 > >> New Revision: 223307 > >> URL: http://svn.freebsd.org/changeset/base/223307 > >> > >> Log: > >> Precisely document the synchronization rules for the page's dirty field. > >> (Saying that the lock on the object that the page belongs to must be held > >> only represents one aspect of the rules.) > >> > >> Eliminate the use of the page queues lock for atomically performing read- > >> modify-write operations on the dirty field when the underlying architecture > >> supports atomic operations on char and short types. > >> > >> Document the fact that 32KB pages aren't really supported. > > > > contrary to the tinderbox I'd like to point out that all mips kernels built by universe are broken with a SVN HEAD from earlier today. Could you please check and see if you can fix it? The errors I get are: > > > > vm_page.o: In function `vm_page_clear_dirty': > > /sys/vm/vm_page.c:(.text+0x18d0): undefined reference to `atomic_clear_8' > > /sys/vm/vm_page.c:(.text+0x18d0): relocation truncated to fit: R_MIPS_26 against `atomic_clear_8' > > vm_page.o: In function `vm_page_set_validclean': > > /sys/vm/vm_page.c:(.text+0x38f0): undefined reference to `atomic_clear_8' > > /sys/vm/vm_page.c:(.text+0x38f0): relocation truncated to fit: R_MIPS_26 against `atomic_clear_8' > > Atomic types shorter than int cannot be used in MI code, since they might > not exist. Apparently they don't exist on mips. jake@ fixed all their > old uses for sparc4 in ~Y2K. I agree. Is there any harm in having the 'dirty' and 'valid' fields in vm_page always be at least of size 'int'? In the case of amd64, vm_page would change from a size of 120 bytes to 128. On i386 I think you'd end up changing the size from 68 to 76. (Using an int results in alignment padding after 'busy'.) Hmm, that's around 120k of extra vm_page_t space for a machine with 64M of RAM, so around 0.18% of RAM would be used on both platforms (presumably the usage would be similar on other platforms as well). At 24 GB of RAM, the extra space is just under 0.20% of RAM (48M). -- John Baldwin
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