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* 2.6.29 pat issue
@ 2009-02-05 12:47 Thomas Hellström
  2009-02-05 18:03 ` Pallipadi, Venkatesh
  0 siblings, 1 reply; 33+ messages in thread
From: Thomas Hellström @ 2009-02-05 12:47 UTC (permalink / raw)
  To: Linux kernel mailing list

Hi!

The function in include/linux/mm.h:
is_linear_pfn_mapping()

doesn't seem valid to me.

In particular, we have VMAs to graphics devices in which vma->vm_pgoff 
is non-zero (Points to an offset in the drm device node), and the VMA is 
sparsely populated with pfns pointing to uncached discontigous RAM pages.

This causes the X86 PAT code to hit the optimized path when it 
shouldn't, and issue a warning.

Also a question about the philosofy behind this strict checking that all 
PTEs have the same caching attributes: I guess this is only to catch 
bugs in kernel drivers that don't get this right. At the same time, now 
that also user-space VMAs are checked this will probably have a 
significant performance impact. Shouldn't this checking really live 
behind a debug define?

Thanks,
Thomas




^ permalink raw reply	[flat|nested] 33+ messages in thread

end of thread, other threads:[~2009-03-14  8:56 UTC | newest]

Thread overview: 33+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-02-05 12:47 2.6.29 pat issue Thomas Hellström
2009-02-05 18:03 ` Pallipadi, Venkatesh
2009-02-05 21:32   ` Thomas Hellstrom
2009-02-05 23:08     ` Pallipadi, Venkatesh
2009-02-06  9:51       ` Thomas Hellström
2009-02-06  1:11     ` Eric W. Biederman
2009-02-06  9:43       ` Thomas Hellström
2009-03-04  6:08         ` Pallipadi, Venkatesh
2009-03-04  9:56           ` Thomas Hellstrom
2009-03-06 22:38             ` Pallipadi, Venkatesh
2009-03-06 23:44               ` Thomas Hellstrom
2009-03-10  1:39                 ` Pallipadi, Venkatesh
2009-03-10  8:22                   ` Thomas Hellstrom
2009-03-10 17:42                     ` Pallipadi, Venkatesh
2009-03-11  9:17                       ` Thomas Hellstrom
2009-03-11  9:33                         ` Ingo Molnar
2009-03-11 17:54                           ` [PATCH] VM, x86, PAT: Change implementation of is_linear_pfn_mapping Pallipadi, Venkatesh
2009-03-11 22:09                             ` Frans Pop
2009-03-12  0:31                               ` Pallipadi, Venkatesh
2009-03-12  3:22                                 ` Pallipadi, Venkatesh
2009-03-12  5:45                                 ` Frans Pop
2009-03-12 18:59                                   ` Pallipadi, Venkatesh
2009-03-12 20:30                                     ` Frans Pop
2009-03-12 22:48                                       ` Pallipadi, Venkatesh
2009-03-13  0:36                                         ` Ingo Molnar
2009-03-13  0:45                                           ` [PATCH] VM, x86, PAT: Change is_linear_pfn_mapping to not use vm_pgoff Pallipadi, Venkatesh
2009-03-13  4:03                                             ` [tip:x86/urgent] " Pallipadi, Venkatesh
2009-03-13 16:25                                               ` Nick Piggin
2009-03-13 17:00                                                 ` Pallipadi, Venkatesh
2009-03-14  2:52                                                   ` Nick Piggin
2009-03-13 23:35                                                 ` [PATCH] Add a new vm flag to track full pfnmap at mmap Pallipadi, Venkatesh
2009-03-14  2:53                                                   ` Nick Piggin
2009-03-14  8:54                                                   ` [tip:x86/urgent] VM, x86, PAT: add " Pallipadi, Venkatesh

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