On Tue, 2012-04-03 at 10:03 +0400, Konstantin Khlebnikov wrote: > Suresh Siddha wrote: > > Konstantin, > > > > On Sat, 2012-03-31 at 21:09 +0400, Konstantin Khlebnikov wrote: > >> v2: Do not use batched pfn reserving for single-page VMA. This is not optimal > >> and breaks something, because I see glitches on the screen with i915/drm driver. > >> With this version glitches are gone, and I see the same regions in > >> /sys/kernel/debug/x86/pat_memtype_list as before patch. So, please review this > >> carefully, probably I'm wrong somewhere, or I have triggered some hidden bug. > > > > Actually it is not a hidden bug. In the original code, we were setting > > VM_PFN_AT_MMAP only for remap_pfn_range() but not for the vm_insert_pfn(). > > Also the value of 'vm_pgoff' depends on the driver/mmap_region() in the case of > > vm_insert_pfn(). But with your proposed code, you were setting > > the VM_PAT for the single-page VMA also and end-up using wrong vm_pgoff in > > untrack_pfn_vma(). > > But I set correct vma->vm_pgoff together with VM_PAT. But, it shouldn't work if vma is expandable... > Also, I am not sure if we can override vm_pgoff in the fault handling path. For example, looking at unmap_mapping_range_tree() it does depend on the vm_pgoff value and it might break if we change the vm_pgoff in track_pfn_vma_new() (which gets called from vm_insert_pfn() as part of the i915_gem_fault()). thanks, suresh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>