linux-kernel - Re: [PATCH -V11 3/3] memory tiering: skip to scan fast memory

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Message-ID: <YgFbmxRR4QC7CJKb@cmpxchg.org>
Date:   Mon, 7 Feb 2022 12:49:15 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Huang Ying <ying.huang@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Feng Tang <feng.tang@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
        Wei Xu <weixugc@...gle.com>, osalvador <osalvador@...e.de>,
        Shakeel Butt <shakeelb@...gle.com>,
        zhongjiang-ali <zhongjiang-ali@...ux.alibaba.com>
Subject: Re: [PATCH -V11 3/3] memory tiering: skip to scan fast memory

On Fri, Jan 28, 2022 at 04:27:51PM +0800, Huang Ying wrote:
> If the NUMA balancing isn't used to optimize the page placement among
> sockets but only among memory types, the hot pages in the fast memory
> node couldn't be migrated (promoted) to anywhere.  So it's unnecessary
> to scan the pages in the fast memory node via changing their PTE/PMD
> mapping to be PROT_NONE.  So that the page faults could be avoided
> too.
> 
> In the test, if only the memory tiering NUMA balancing mode is enabled, the
> number of the NUMA balancing hint faults for the DRAM node is reduced to
> almost 0 with the patch.  While the benchmark score doesn't change
> visibly.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Suggested-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Tested-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Rik van Riel <riel@...riel.com>
> Cc: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Yang Shi <shy828301@...il.com>
> Cc: Zi Yan <ziy@...dia.com>
> Cc: Wei Xu <weixugc@...gle.com>
> Cc: osalvador <osalvador@...e.de>
> Cc: Shakeel Butt <shakeelb@...gle.com>
> Cc: zhongjiang-ali <zhongjiang-ali@...ux.alibaba.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-mm@...ck.org

Looks good to me.

Acked-by: Johannes Weiner <hannes@...xchg.org>