From owner-svn-src-head@FreeBSD.ORG Wed Jun 10 07:00:02 2009 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0EAAD10656CA; Wed, 10 Jun 2009 07:00:02 +0000 (UTC) (envelope-from marck@rinet.ru) Received: from woozle.rinet.ru (woozle.rinet.ru [195.54.192.68]) by mx1.freebsd.org (Postfix) with ESMTP id 602A28FC12; Wed, 10 Jun 2009 07:00:01 +0000 (UTC) (envelope-from marck@rinet.ru) Received: from localhost (localhost [127.0.0.1]) by woozle.rinet.ru (8.14.3/8.14.3) with ESMTP id n5A7000G050789; Wed, 10 Jun 2009 11:00:00 +0400 (MSD) (envelope-from marck@rinet.ru) Date: Wed, 10 Jun 2009 11:00:00 +0400 (MSD) From: Dmitry Morozovsky To: Kip Macy In-Reply-To: <3c1674c90906092324n58e16154s6800e61752282e42@mail.gmail.com> Message-ID: References: <200906100121.n5A1LWVO089719@svn.freebsd.org> <3c1674c90906092324n58e16154s6800e61752282e42@mail.gmail.com> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) X-NCC-RegID: ru.rinet X-OpenPGP-Key-ID: 6B691B03 MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (woozle.rinet.ru [0.0.0.0]); Wed, 10 Jun 2009 11:00:00 +0400 (MSD) Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r193878 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Jun 2009 07:00:03 -0000 On Tue, 9 Jun 2009, Kip Macy wrote: KM> > KM>   As far as I can tell systems that have less than 4GB are more often hurt KM> > KM>   by prefetched than helped.  On i386 systems and systems with less than 4GB, KM> > KM>   prefetch is now disabled by default. I've added a prefetch enable tunable, to KM> > KM>   enable prefetching for those systems. The prefetch disable tunable will continue KM> > KM>   to unconditionally disable prefetching. KM> > KM> KM> > KM> > [snip] KM> > KM> > KM> +extern int zfs_prefetch_disable; KM> > KM> +extern int zfs_prefetch_enable; KM> > KM> > [snip] KM> > KM> > Before the interface is not settled in stone, don't you think simple bool KM> > zfs_prefetch tunable (defauled to what looks more reasonable to partucilar KM> > arch/memsize) is more clean and straightforward? KM> > KM> KM> Yes. But the semantics I want don't lend themselves well to a boolean. KM> I want it to default to off for i386 and amd64 w/ < 4GB and on for KM> amd64 > 4GB. However, I want it to be possible for users with larger KM> memory systems to disable it and users with smaller memory systems to KM> enable it. The only way a simple boolean would work would be if it KM> were zfs_prefetch_non_default_behavior, which I think is even more KM> confusing than what I have now. Hmm, I failed to see how boolean prevent the usage: if arch==i386 || memsize < 4G zfs_prefetch=0 else zfs_prefetch=1 and admin can flip the switch to non-default position. Or, do you think it's not clean for the user? -- Sincerely, D.Marck [DM5020, MCK-RIPE, DM3-RIPN] [ FreeBSD committer: marck@FreeBSD.org ] ------------------------------------------------------------------------ *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru *** ------------------------------------------------------------------------