linux-kernel - Re: [PATCH -mm] autonuma: Fix scan period updating

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Date:   Mon, 24 Jun 2019 15:09:50 +0100
From:   Mel Gorman <mgorman@...e.de>
To:     Huang Ying <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, jhladky@...hat.com,
        lvenanci@...hat.com, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH -mm] autonuma: Fix scan period updating

On Mon, Jun 24, 2019 at 10:56:04AM +0800, Huang Ying wrote:
> The autonuma scan period should be increased (scanning is slowed down)
> if the majority of the page accesses are shared with other processes.
> But in current code, the scan period will be decreased (scanning is
> speeded up) in that situation.
> 
> This patch fixes the code.  And this has been tested via tracing the
> scan period changing and /proc/vmstat numa_pte_updates counter when
> running a multi-threaded memory accessing program (most memory
> areas are accessed by multiple threads).
> 

The patch somewhat flips the logic on whether shared or private is
considered and it's not immediately obvious why that was required. That
aside, other than the impact on numa_pte_updates, what actual
performance difference was measured and on on what workloads?

-- 
Mel Gorman
SUSE Labs