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Re: [PATCH] mm: vmalloc: Remove double execution of vunmap_page_range






On 4/13/2018 3:29 PM, Anshuman Khandual wrote:
On 04/13/2018 02:46 PM, Chintan Pandya wrote:
Unmap legs do call vunmap_page_range() irrespective of
debug_pagealloc_enabled() is enabled or not. So, remove
redundant check and optional vunmap_page_range() routines.

vunmap_page_range() tears down the page table entries and does
not really flush related TLB entries normally unless page alloc
debug is enabled where it wants to make sure no stale mapping is
still around for debug purpose. Deferring TLB flush improves
performance. This patch will force TLB flush during each page
table tear down and hence not desirable.

Deferred TLB invalidation will surely improve performance. But force
flush can help in detecting invalid access right then and there. I
chose later. May be I should have clean up the vmap tear down code
as well where it actually does the TLB invalidation.

Or make TLB invalidation in free_unmap_vmap_area() be dependent upon
debug_pagealloc_enabled().

Chintan
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