Re: [PATCH] x86,mm: delay TLB flush after clearing accessed bit

[Rik van Riel <riel@redhat.com>]

On 04/01/2014 12:21 PM, Linus Torvalds wrote:
> On Tue, Apr 1, 2014 at 9:11 AM, Rik van Riel <riel@redhat.com> wrote:
>>
>> Memory pressure is not necessarily caused by the same process
>> whose accessed bit we just cleared. Memory pressure may not
>> even be caused by any process's virtual memory at all, but it
>> could be caused by the page cache.
> 
> If we have that much memory pressure on the page cache without having
> any memory pressure on the actual VM space, then the swap-out activity
> will never be an issue anyway.
> 
> IOW, I think all these scenarios are made-up. I'd much rather go for
> simpler implementation, and make things more complex only in the
> presence of numbers. Of which we have none.

We've been bitten by the lack of a properly tracked accessed
bit before, but admittedly that was with the KVM code and EPT.

I'll add my Acked-by: to Shaohua's original patch then, and
will keep my eyes open for any problems that may or may not
materialize...

Shaohua?

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