Date: Wed, 26 Jun 2002 02:46:25 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Peter Wemm <peter@wemm.org>, Alfred Perlstein <bright@mu.org>, Patrick Thomas <root@utility.clubscholarship.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: tunings for many httpds... Message-ID: <3D198D71.86779927@mindspring.com> References: <20020625222632.B7C7D3811@overcee.wemm.org> <3D1970E7.697D4A49@mindspring.com> <200206260758.g5Q7wPgZ019100@apollo.backplane.com>
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Matthew Dillon wrote: > Hmm. I'm fairly sure that Linux does not quite do it that way. I > believe the 2-level page tables are copy-on-write, but that only > gives you shareability across a fork() and then only for a little > while. I'm fairly certain that Linux cannot share page tables > for post-fork modifications (like when you mmap() or get a SysV > shared segment). The rmap patches are roughly equivalent to our > i386 pmap code and allow Rik to implement page queues and proper page > aging. I wasn't saying that they were shared on the mmap(); Peter had suggested it for FreeBSD. Also "a little while" is relative; as long as you don't write the page, it should stay shared. That basically means that all instances of apache share mappings on the code pages. Here's the article I was reading in one window while typing in the other. It's linked off the article reference I posted to -arch earlier: http://old.lwn.net/2002/0124/kernel.php3 "What Rik van Riel is up to." FWIW: In the original Article: http://lwn.net/Articles/3327/ they say they've gon to a 3 level page table scheme for the Hammer port. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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