Date: Tue, 25 Jun 2002 15:26:32 -0700 From: Peter Wemm <peter@wemm.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Alfred Perlstein <bright@mu.org>, Terry Lambert <tlambert2@mindspring.com>, Patrick Thomas <root@utility.clubscholarship.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: tunings for many httpds... Message-ID: <20020625222632.B7C7D3811@overcee.wemm.org> In-Reply-To: <200206252209.g5PM9J79010543@apollo.backplane.com>
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Matthew Dillon wrote: > > : > :This is also the _default_ for how solaris manages sysv segments, > :although it would be nice if we could get the OBJT_PHYS stuff to > :use 4meg pages (unless someone already did that?)... > : > :Anyhow, I'm glad we corrected your misconception and we now have > :a more accurate understanding of how this system works. > : > :-Alfred > > Even more importantly it would be nice if we could share compatible > pmap pages, then we would have no need for 4MB pages... 50 mappings > of the same shared memory segment would wind up using the same pmap > pages as if only one mapping had been made. Such a feature would work > for SysV shared memory and for mmap()s. I've looked at doing this > off and on for two years but do not have a sufficient chunk of time > available yet. SVR4/Solaris/Digital Unix^H^H^H^H^H^HTru64 do this by having an additional layer between VM and pmap. The equivalent of our pmap is just another one of the address space handlers. The SHM stuff etc is often implemented such that it grabbed blocks of 4MB address space to manage in a way that it likes. This means it constructs its own page tables etc in such a way that they are suitable for common use. *If* I recall correctly, in SunOS/SVR4/ Solaris parlance this is the segment layer. Naturally there is quite a bit of variation. It has been a long long time since I looked at this. Cheers, -Peter -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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