From owner-freebsd-hackers Mon Feb 12 16:23:24 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from winston.osd.bsdi.com (winston.osd.bsdi.com [204.216.27.229]) by hub.freebsd.org (Postfix) with ESMTP id A89BE37B491 for ; Mon, 12 Feb 2001 16:23:22 -0800 (PST) Received: from winston.osd.bsdi.com (jkh@localhost [127.0.0.1]) by winston.osd.bsdi.com (8.11.2/8.11.1) with ESMTP id f1D0MbH79727; Mon, 12 Feb 2001 16:22:38 -0800 (PST) (envelope-from jkh@winston.osd.bsdi.com) To: Greg Lehey Cc: Dag-Erling Smorgrav , Danny Braniss , Matt Dillon , freebsd-hackers@FreeBSD.ORG Subject: Re: soft updates performance In-Reply-To: Message from Greg Lehey of "Tue, 13 Feb 2001 09:53:00 +1030." <20010213095300.D2178@wantadilla.lemis.com> Date: Mon, 12 Feb 2001 16:22:37 -0800 Message-ID: <79723.982023757@winston.osd.bsdi.com> From: Jordan Hubbard Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > In fact, it's exactly the opposite. 'make world' is CPU-bound, so the > speed of the I/O system is irrelevant. If it were I/O bound, soft > updates *would* make a difference, because a number of unnecessary > writes would be eliminated. Actually, I have measured that after a certain point make world *is* I/O bound and you can't really get any faster unless you do something to the I/O subsystem. We have several quad Xeons here, and back when I was more interested in measuring this sort of thing I found that I could get a "worldstone" time of around 37 minutes with -j8 and all 4 processors churning away. This was also during the exclusively BGL days of -current and things may scale slightly better or worse now, I dunno, but what I did find was that I could drop this all to something more like 23 minutes simply by putting /usr/src and /usr/obj into MFS (the machine I used also has a gigabyte of memory so this isn't difficult to do). That implies to me, at least, that after a certain point the CPU is going to be the bottleneck. - Jordan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message