Date: Sat, 22 Apr 2000 15:19:55 -0400 (EDT) From: Brian Fundakowski Feldman <green@FreeBSD.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Alfred Perlstein <bright@wintelcom.net>, Kevin Day <toasty@dragondata.com>, hackers@FreeBSD.ORG Subject: Re: Double buffered cp(1) Message-ID: <Pine.BSF.4.21.0004221518200.13126-100000@green.dyndns.org> In-Reply-To: <200004221706.KAA55294@apollo.backplane.com>
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On Sat, 22 Apr 2000, Matthew Dillon wrote: > > :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] > > Probably not so good considering the number of faults that will > be taken. Also, if the destination filesystem runs out of room > cp will take a random seg-fault trying to access the map. Plus > the dirtying of that many VM pages will seriously effect performance. Err... I think what Alfred (should have) meant was that you should mmap the source file and madvise it MADV_SEQUENTIAL, then write() to the new file directly from that. How bad do you foresee performance being then? -- Brian Fundakowski Feldman \ FreeBSD: The Power to Serve! / green@FreeBSD.org `------------------------------' To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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