From owner-freebsd-hackers Mon Feb 12 15:23: 8 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from wantadilla.lemis.com (wantadilla.lemis.com [192.109.197.80]) by hub.freebsd.org (Postfix) with ESMTP id 602C837B503 for ; Mon, 12 Feb 2001 15:23:03 -0800 (PST) Received: by wantadilla.lemis.com (Postfix, from userid 1004) id EC2A26ACC8; Tue, 13 Feb 2001 09:53:00 +1030 (CST) Date: Tue, 13 Feb 2001 09:53:00 +1030 From: Greg Lehey To: Dag-Erling Smorgrav Cc: Danny Braniss , Matt Dillon , freebsd-hackers@FreeBSD.ORG Subject: Re: soft updates performance Message-ID: <20010213095300.D2178@wantadilla.lemis.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from des@ofug.org on Mon, Feb 12, 2001 at 03:29:17PM +0100 Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.lemis.com/~grog X-PGP-Fingerprint: 6B 7B C3 8C 61 CD 54 AF 13 24 52 F8 6D A4 95 EF Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Monday, 12 February 2001 at 15:29:17 +0100, Dag-Erling Smorgrav wrote: > Danny Braniss writes: >> i've been doing some experiments with vinum, and doing a make buildworld >> (with obj on the same vinum) >> without soft-updates ~ 1 hour >> with soft-updates ~ 40 minutes >> which is a bit better than 3% :-) >> >> what i can't figure out is why -j 4 didn't make any difference. > > Because your I/O system is already saturated. The point with -jNN is > that one job can run while another is waiting for I/O to complete and > vice versa, but as your CPU gets faster the time spent actually > compiling etc. becomes insignificant next to the time spent doing I/O, > and if you're already doing I/O as fast as you can there's no room for > improvement. On a machine with a slower CPU or a faster I/O system, > you'd see improvement. 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. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message