linux-kernel - Re: [PATCH v4 10/10] x86/mm: Try to preserve old TLB entries using PCID

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Date:   Mon, 3 Jul 2017 12:56:45 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 10/10] x86/mm: Try to preserve old TLB entries using
 PCID

On Thu, 29 Jun 2017, Andy Lutomirski wrote:
> ping-pong between two mms on the same CPU using eventfd:
>   patched:         1.22µs
>   patched, nopcid: 1.33µs
>   unpatched:       1.34µs
> 
> Same ping-pong, but now touch 512 pages (all zero-page to minimize
> cache misses) each iteration.  dTLB misses are measured by
> dtlb_load_misses.miss_causes_a_walk:
>   patched:         1.8µs  11M  dTLB misses
>   patched, nopcid: 6.2µs, 207M dTLB misses
>   unpatched:       6.1µs, 190M dTLB misses
> 
> Reviewed-by: Nadav Amit <nadav.amit@...il.com>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>