From owner-freebsd-hackers@FreeBSD.ORG Sun Jul 25 20:28:54 2010 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 839071065677 for ; Sun, 25 Jul 2010 20:28:54 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-ww0-f42.google.com (mail-ww0-f42.google.com [74.125.82.42]) by mx1.freebsd.org (Postfix) with ESMTP id 450648FC13 for ; Sun, 25 Jul 2010 20:28:53 +0000 (UTC) Received: by wwf26 with SMTP id 26so2268976wwf.1 for ; Sun, 25 Jul 2010 13:28:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:received:received:date:from:to:subject :message-id:in-reply-to:references:x-mailer:mime-version :content-type:content-transfer-encoding; bh=xiKsSYWPKBjVqgiw15IxND+oktrVcFIGgbQe6f3FOgE=; b=ngAELpadb3V2LUS/r/D64X4MXF02oWR2EGOEhT5bGDQtC9tP6eVnZf9OVfTb6qC7CL +aUCZC9OjnT77vJGONK/g+hdkkF3Dchu+MZmjD3zVqnCSTuz9PNK++SsSO2b6NMlDeq7 d9oWX4klKdQPOPcOhL4NdMLLKvsKz5daf14JE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=date:from:to:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; b=cMlivFKKM3Xl9B98y2bkG+t0sRMTrJWhbPAKEFqV7ncgFiTAGW6vZWuXHzafxgb+3W nfaLFCWkhS1QKy48i1wkW7aCjy1EsOtMWlj3EnrGN2SQ/jDNXcMn6iNfS+Bvhr+IRDHQ W1N1my0v7jwzoWV8nOJ5fw2m4ZHBFQ5Nb6q3M= Received: by 10.227.146.147 with SMTP id h19mr6344713wbv.222.1280089732914; Sun, 25 Jul 2010 13:28:52 -0700 (PDT) Received: from gumby.homeunix.com (bb-87-81-140-128.ukonline.co.uk [87.81.140.128]) by mx.google.com with ESMTPS id e31sm2397228wbe.23.2010.07.25.13.28.51 (version=SSLv3 cipher=RC4-MD5); Sun, 25 Jul 2010 13:28:52 -0700 (PDT) Date: Sun, 25 Jul 2010 21:28:49 +0100 From: RW To: freebsd-hackers@freebsd.org 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> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i386-portbld-freebsd8.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: pageout question X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 25 Jul 2010 20:28:54 -0000 On Sun, 25 Jul 2010 17:19:41 +0300 Andriy Gapon 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.