From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ray Bryant" Subject: Re: [PATCH/RFC] Shared page tables Date: Mon, 23 Jan 2006 18:46:07 -0600 References: <200601231758.08397.raybry@mpdtxmail.amd.com> <6BC41571790505903C7D3CD6@[10.1.1.4]> In-Reply-To: <6BC41571790505903C7D3CD6@[10.1.1.4]> MIME-Version: 1.0 Message-ID: <200601231846.08594.raybry@mpdtxmail.amd.com> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Dave McCracken Cc: Robin Holt , Hugh Dickins , Linux Kernel , Linux Memory Management List-ID: On Monday 23 January 2006 18:19, Dave McCracken wrote: > > The basic rule for pte sharing is that some portion of a memory region must > span an entire pte page. For i386 and x96_64 that would be 2 meg. The > region must either be read-only or marked to be shared if it is writeable. > Yeah, I figured that out just after hitting "send" on that first note. :-( > The code does opportunistically look for any pte page that is fully within > a shareable vma, and will share if it finds one. > > Oh, and one more caveat. The region must be mapped to the same address in > each process. > > > I turned on the PT_DEBUG stuff, but thus far have found no evidence of > > pte sharing actually occurring in a normal system boot. I'm surprised > > by that as I (naively?) would have expected shared libraries to use > > shared ptes. > OK, with those guidelines I can put together a test program pretty quickly. If you have one handy that would be fine, but don't put a lot of effort into it. Thanks, > Most system software, including the shared libraries, don't have any > regions that are big enough for sharing (the text section for libc, for > example, is about 1.5 meg). > Ah, that explains that then. > Dave McCracken -- Ray Bryant AMD Performance Labs Austin, Tx 512-602-0038 (o) 512-507-7807 (c) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org