Date: Sat, 22 Apr 2000 01:20:05 -0700 From: Alfred Perlstein <bright@wintelcom.net> To: Kevin Day <toasty@dragondata.com> Cc: hackers@FreeBSD.ORG Subject: Re: Double buffered cp(1) Message-ID: <20000422012005.A204@fw.wintelcom.net> In-Reply-To: <200004220255.VAA29433@celery.dragondata.com>; from toasty@dragondata.com on Fri, Apr 21, 2000 at 09:55:19PM -0500 References: <200004220255.VAA29433@celery.dragondata.com>
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* Kevin Day <toasty@dragondata.com> [000421 20:24] wrote: > > Has anyone attempted to create a double buffered version of cp(1)? When > copying from one disk to another, disk activity seems to ping-pong between > the two, rather than keeping both active at the same time. > > If I were to fork and do something similar to afio, or maybe even doing > something weird like using sendfile(it's faster than it sounds, and > zero-copy), does anyone think I'd see any kind of speed boost? > > I'm effectively getting a little less than half the performance of just > writing files filled with zero's, so I'm guessing this is where the > bottleneck is, correct? extend (using truncate) and then mmap() the destination file, then read() directly into the mmap()'d portion. I'd like to see what numbers you get. :) -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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