Date: Sun, 25 Jul 2010 21:28:49 +0100 From: RW <rwmaillists@googlemail.com> To: freebsd-hackers@freebsd.org Subject: Re: pageout question Message-ID: <20100725212849.1e07f40c@gumby.homeunix.com> In-Reply-To: <4C4C47FD.6080802@freebsd.org> References: <4C4B4BAB.3000005@freebsd.org> <20100725003144.3cfead39@gumby.homeunix.com> <4C4C0CD9.6000002@freebsd.org> <20100725144141.6f1f33cc@gumby.homeunix.com> <4C4C47FD.6080802@freebsd.org>
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On Sun, 25 Jul 2010 17:19:41 +0300 Andriy Gapon <avg@freebsd.org> wrote: > on 25/07/2010 16:41 RW said the following: > > In FreeBSD the inactive queue contains disk cache pages which > > normally provide most of the clean pages needed. In addition pages > > are dribbled out to swap, and the resulting clean pages are placed > > at the back of the inactive queue to make another pass. > > Well, "normally" and "most" are not quite quantitative. > Personally, I do not see any guarantees that inactive queue would > contain enough clean pages to reach paging target on a single pass. I didn't say it say it was guaranteed. I just think the scenario where a first pass ends up between the watermarks is rare. And when it happens I don't see a compelling reason to do extra paging to reach an arbitrary target. I think the comment about not clearing vm_pages_needed is referring to clearing it below the low-watermark because the daemon would then get woken-up almost immediately. > I meant bare minimum to stop paging, that is, going above lower > watermark of the paging hysteresis.
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