Subject: Re: [PATCH v4 5/5] x86: mremap speedup - Enable HAVE_MOVE_PUD

From: Ingo Molnar <[email-masked]>
Date: Wed, 14 Oct 2020 17:53:18 +0200

* Kalesh Singh <[email-masked]> wrote:

> HAVE_MOVE_PUD enables remapping pages at the PUD level if both the
> source and destination addresses are PUD-aligned.
> 
> With HAVE_MOVE_PUD enabled it can be inferred that there is approximately
> a 13x improvement in performance on x86. (See data below).
> 
> ------- Test Results ---------
> 
> The following results were obtained using a 5.4 kernel, by remapping
> a PUD-aligned, 1GB sized region to a PUD-aligned destination.
> The results from 10 iterations of the test are given below:
> 
> Total mremap times for 1GB data on x86. All times are in nanoseconds.
> 
> Control        HAVE_MOVE_PUD
> 
> 180394         15089
> 235728         14056
> 238931         25741
> 187330         13838
> 241742         14187
> 177925         14778
> 182758         14728
> 160872         14418
> 205813         15107
> 245722         13998
> 
> 205721.5       15594    <-- Mean time in nanoseconds
> 
> A 1GB mremap completion time drops from ~205 microseconds
> to ~15 microseconds on x86. (~13x speed up).
> 
> Signed-off-by: Kalesh Singh <[email-masked]>
> Acked-by: Kirill A. Shutemov <[email-masked]>
> Cc: Andrew Morton <[email-masked]>
> Cc: Thomas Gleixner <[email-masked]>
> Cc: Ingo Molnar <[email-masked]>
> Cc: Borislav Petkov <[email-masked]>
> Cc: H. Peter Anvin <[email-masked]>

Nice!

Assuming it's all correct code:

Acked-by: Ingo Molnar <[email-masked]>

Thanks,

	Ingo

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