Messages in this thread | | | From | "Ray Bryant" <> | Subject | Re: [PATCH/RFC] Shared page tables | Date | Mon, 23 Jan 2006 18:46:07 -0600 |
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On Monday 23 January 2006 18:19, Dave McCracken wrote: <snip> > > 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)
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