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Subject: Re: Plumbers 2018 - Performance and Scalability Microconference
To:     Thomas Gleixner <tglx@linutronix.de>
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From:   Laurent Dufour <ldufour@linux.vnet.ibm.com>
Date:   Thu, 6 Sep 2018 09:45:05 +0200
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On 06/09/2018 01:01, Thomas Gleixner wrote:
> On Wed, 5 Sep 2018, Laurent Dufour wrote:
>> On 05/09/2018 17:10, Christopher Lameter wrote:
>>> Large page sizes also reduce contention there.
>>
>> That's true for the page fault path, but for process's actions manipulating the
>> memory process's layout (mmap,munmap,madvise,mprotect) the impact is minimal
>> unless the code has to manipulate the page tables.
> 
> And how exactly are you going to do any of those operations _without_
> manipulating the page tables?

I agree, at one time the page tables would have to be manipulated, and this is
mostly done under the protection of the page table locks - should the mmap_sem
still being held then ?

I was thinking about all the processing done on the VMAs, accounting, etc.
That part, usually not manipulating the page tables, is less dependent of the
underlying page size.

But I agree at one time of the processing, the page table are manipulated and
dealing with larger pages is better then.

Thanks,
Laurent.