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Date: Thu, 30 Mar 2000 08:51:34 -0800 (PST)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <200003301651.IAA73393@apollo.backplane.com>
To: Peter Wemm <peter@netplex.com.au>
Cc: "Daniel O'Connor" <doconnor@gsoft.com.au>, cvs-all@FreeBSD.ORG,
	cvs-committers@FreeBSD.ORG
Subject: Re: cvs commit: src/sys/alpha/include vmparam.h src/sys/conf opt 
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:
:Matthew Dillon wrote:
:> :
:> :"Daniel O'Connor" wrote:
:> :> 
:> :> On 30-Mar-00 Peter Wemm wrote:
:> :> >    that comment is bogus..  The only practical limit is how much physica
:    l
:> :> >    ram you want to lock up as this stuff isn't paged out or swap backed.
:> :> 
:> :> Is it [easily] possible to make its pageable? 
:> :
:> :I don't know.  Probably, if one wanted to cut/paste code from the likes
:> :of the swap-backed code in the vn device.
:> 
:>     I couldn't find the beginning of this thread, but if you are talking
:>     about making the PV entries pageable, it isn't possible.
:
:No, the shared memory segments themselves, not the PV entries.  Presently
:the pages are wired directly into the processes that attach to them and
:they are not pageable.  (which is a distinct advantage over using mmap for
:temporary storage if you don't want pagedaemon messing with it - even for
:MAP_ANON)
:
:Cheers,
:-Peter

    I'm still confused.  SysV shared memory segments are swap-backed.

    Even if they weren't, the useage pattern may be random enough that it
    won't save on the PV entries or page table pages.

					-Matt
					Matthew Dillon 
					<dillon@backplane.com>


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