From owner-freebsd-hackers Sun Dec 15 12:21:17 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0C47137B401 for ; Sun, 15 Dec 2002 12:21:16 -0800 (PST) Received: from rootlabs.com (root.org [67.118.192.226]) by mx1.FreeBSD.org (Postfix) with SMTP id 4CE9043EC2 for ; Sun, 15 Dec 2002 12:21:15 -0800 (PST) (envelope-from nate@rootlabs.com) Received: (qmail 44827 invoked by uid 1000); 15 Dec 2002 20:21:16 -0000 Date: Sun, 15 Dec 2002 12:21:16 -0800 (PST) From: Nate Lawson To: phk@FreeBSD.ORG Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: setattr() syscall as proposed by phk In-Reply-To: <49290.1039943534@critter.freebsd.dk> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sun, 15 Dec 2002 phk@FreeBSD.ORG wrote: > Nate Lawson writes: > >I don't mean to be rude but I doubt the utility of this whole > >plan. dump/restore are done on disk devices which are at least an order > >of magnitude slower than a syscall boundary crossing. Going from 4 > >syscalls to 1 can't make a bit of difference in restore(8) performance. > > You are wrong about restore: restore is done on a mounted filesystem. Heh, you took that too literally. I meant the IO is coming from a tape, disk, or other physical media device where latencies for a 32-64k xfer are usually on the order of 1-10 ms or more. > >So why is this faster? Something is likely slowing namei() down. > > Because 1 syscall and 2 namei calls are faster than 4 syscalls and > four namei calls. Which leaves us back at my previous point which is that something is wrong with caching if 4 namei calls (for the SAME name) are so much slower. A great task would be to examine/test namei(), identify why it's not cached correctly, and fix the underlying problem. The syscall boundary crossing is NOT significant here. -Nate "One hand for your own code, and one hand for the infrastructure". -- phk To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message