From owner-freebsd-hackers@FreeBSD.ORG Mon Jul 26 17:53:56 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 4B91A1065674 for ; Mon, 26 Jul 2010 17:53:56 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-wy0-f182.google.com (mail-wy0-f182.google.com [74.125.82.182]) by mx1.freebsd.org (Postfix) with ESMTP id D09BF8FC17 for ; Mon, 26 Jul 2010 17:53:55 +0000 (UTC) Received: by wyj26 with SMTP id 26so2847735wyj.13 for ; Mon, 26 Jul 2010 10:53:54 -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=GiYkcUGb5QlxxMiNTgWsntXXs7CQ8p5NUnU9HoLq+2o=; b=RHVgfEkrQsr3A4fGGFwt49QAgfYcX47e4LAPnlJcrPqJlC/zKpzoUfJfaaRZiaZamu Z6jJoPMzx5iVd7kErH/J9D9BOhkU27CMBdVKSObcUBOTLglvvv0WH2NDp6djEkkCn4hd 9MpLs+eXKJTz37o3kaVWIQm3K0EKW5Z5QdVTU= 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=e/bBCOjwvFxXJd1ehmvNCCm1Uwzu30OjldZhi8wILA2QgpZTW7RpzfvegyPKqZlIgf wWNVvUc0UbuA+M6Z2ckk4wnR6im14MGGRTxWNSpMoALfTv+pLeVI7o6JC88f4Dmpg0aJ 68Yp2tINY30cVh62vFnSF2uvvYQDmbwITyy3k= Received: by 10.227.144.129 with SMTP id z1mr7691304wbu.85.1280166834752; Mon, 26 Jul 2010 10:53:54 -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 l6sm2105804wed.25.2010.07.26.10.53.49 (version=SSLv3 cipher=RC4-MD5); Mon, 26 Jul 2010 10:53:51 -0700 (PDT) Date: Mon, 26 Jul 2010 18:53:48 +0100 From: RW To: freebsd-hackers@freebsd.org Message-ID: <20100726185348.63ebf916@gumby.homeunix.com> In-Reply-To: <4C4CA1DC.2050902@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> <20100725212849.1e07f40c@gumby.homeunix.com> <4C4CA1DC.2050902@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: Mon, 26 Jul 2010 17:53:56 -0000 On Sun, 25 Jul 2010 23:43:08 +0300 Andriy Gapon wrote: > on 25/07/2010 23:28 RW said the following: > > 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. > > Well, it seems neither I nor you have data to show whether it's rare > or not (and it would greatly depend on workload too). > As to "arbitrary target" - well, that's the whole point of > hysteresis-like behavior. We start paging also at an "arbitrary" > point. If after the first pass with light-paging the high watermark isn't reached then the choices are 1) loop and immediately do a heavy-paging pass. 2) wait and let the daemon get woken-up for another light-paging pass - only go to heavy-paging when this strategy isn't keeping up with demand. To me (2) is doing the right thing. It's trying to satisfy demand from existing clean pages, and only paging heavily as a last resort.