Re: [PATCH v2 RESEND] x86: optimize memcpy_flushcache

From: Ingo Molnar
Date: Thu Jun 21 2018 - 10:31:48 EST



* Mike Snitzer <snitzer@xxxxxxxxxx> wrote:

> From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Subject: [PATCH v2] x86: optimize memcpy_flushcache
>
> In the context of constant short length stores to persistent memory,
> memcpy_flushcache suffers from a 2% performance degradation compared to
> explicitly using the "movnti" instruction.
>
> Optimize 4, 8, and 16 byte memcpy_flushcache calls to explicitly use the
> movnti instruction with inline assembler.

Linus requested asm optimizations to include actual benchmarks, so it would be
nice to describe how this was tested, on what hardware, and what the before/after
numbers are.

Thanks,

Ingo