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

[Chintan Pandya]

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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