On Fri, 21 Apr 2006, Zoltan Menyhart wrote: > Christoph Lameter wrote: > > On Fri, 21 Apr 2006, Zoltan Menyhart wrote: > > > > > - it scales well > > > > mmap_sem is the major performance bottleneck for page faults at this time > > because it creates a bouncing cacheline. Figure out a way to avoid that to > > increase performance. > > Have you got some numbers? > Can I have a copy of your test program, please? Test program is available from ftp.kernel.org/pub/linux/kernel/people/christoph/ptl/pft.c. See the discussion of my page fault scalability patches on lkml in 2004/2005. > > The walking of pgd/pud/pmd can happen anytime through the mmu on many > > architectures. It is therefore not protectable by any lock. > > I do not know much about the other architectures. They are relevant since they determine core linux functionality. > If PGD...PTE walking does not need protection / cannot be protected on > other architectures, then it is not a strong argument about the ia64's > behavior. Of course. This means that the core kernel was designed in such a way to cope with this issue. > We were talking about this issue in the thread "accessed/dirty bit > handler tuning". I thought we had agreed that this PGD...PTE walking > is unsafe. I did? > Locking _is_ a logically correct solution. > Any other suggestion? Drop the non issue. > > free_pgtables() is run when all processes in a mm_struct have terminated or > > when all vmas from an area have been removed. > > > > There can be no one using the page tables. > > Please refer to "unmap_region()". Only run after the vmas have been removed. Any fault will lead to an access error. - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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