Messages in this thread | | | Date | Sun, 12 Dec 2004 09:33:11 +0000 (GMT) | From | Hugh Dickins <> | Subject | Re: page fault scalability patch V12 [0/7]: Overview and performance tests |
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On Sun, 12 Dec 2004, Nick Piggin wrote: > Christoph Lameter wrote: > > On Thu, 9 Dec 2004, Hugh Dickins wrote: > > >>probably others (harder to think through). Your 4/7 patch for i386 has > >>an unused atomic get_64bit function from Nick, I think you'll have to > >>define a get_pte_atomic macro and use get_64bit in its 64-on-32 cases. > > > > That would be a performance issue. > > Problems were pretty trivial to reproduce here with non atomic 64-bit > loads being cut in half by atomic 64 bit stores. I don't see a way > around them, unfortunately.
Of course, it'll only be a performance issue in the 64-on-32 cases: the 64-on-64 and 32-on-32 macro should reduce to exactly the present "entry = *pte".
I've had the impression that Christoph and SGI have to care a great deal more about ia64 than the others; and as x86_64 advances, so i386 PAE grows less important. Just so long as a get_64bit there isn't a serious degradation from present behaviour, it's okay.
Oh, hold on, isn't handle_mm_fault's pmd without page_table_lock similarly racy, in both the 64-on-32 cases, and on architectures which have a more complex pmd_t (sparc, m68k, h8300)? Sigh.
Hugh
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