Re: [PATCH v2 7/7] mm: munlock: manual pte walk in fast path instead of follow_page_mask()

[Vlastimil Babka <vbabka@suse.cz>]

On 08/20/2013 12:47 AM, Andrew Morton wrote:
> On Mon, 19 Aug 2013 14:23:42 +0200 Vlastimil Babka <vbabka@suse.cz> wrote:
> 
>> Currently munlock_vma_pages_range() calls follow_page_mask() to obtain each
>> struct page. This entails repeated full page table translations and page table
>> lock taken for each page separately.
>>
>> This patch attempts to avoid the costly follow_page_mask() where possible, by
>> iterating over ptes within single pmd under single page table lock. The first
>> pte is obtained by get_locked_pte() for non-THP page acquired by the initial
>> follow_page_mask(). The latter function is also used as a fallback in case
>> simple pte_present() and vm_normal_page() are not sufficient to obtain the
>> struct page.
> 
> Patch #7 appears to provide significant performance gains, but the
> improvement wasn't individually described here, unlike the other
> patches.

Oops I forgot to mention this here. Can you please add the following to
the comment then? Thanks.

After this patch, a 13% speedup was measured for munlocking a 56GB large
memory area with THP disabled.

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