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Date:   Mon, 7 Feb 2022 12:49:15 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Huang Ying <ying.huang@intel.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Mel Gorman <mgorman@suse.de>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Feng Tang <feng.tang@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Rik van Riel <riel@surriel.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Yang Shi <shy828301@gmail.com>, Zi Yan <ziy@nvidia.com>,
        Wei Xu <weixugc@google.com>, osalvador <osalvador@suse.de>,
        Shakeel Butt <shakeelb@google.com>,
        zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
Subject: Re: [PATCH -V11 3/3] memory tiering: skip to scan fast memory
Message-ID: <YgFbmxRR4QC7CJKb@cmpxchg.org>
References: <20220128082751.593478-1-ying.huang@intel.com>
 <20220128082751.593478-4-ying.huang@intel.com>
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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@intel.com>
> Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Yang Shi <shy828301@gmail.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Wei Xu <weixugc@google.com>
> Cc: osalvador <osalvador@suse.de>
> Cc: Shakeel Butt <shakeelb@google.com>
> Cc: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-mm@kvack.org

Looks good to me.

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