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Date:   Wed, 18 May 2022 12:51:10 -0700
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Subject: Re: [PATCH] Revert "mm/vmscan: never demote for memcg reclaim"
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To:     Johannes Weiner <hannes@cmpxchg.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "Huang, Ying" <ying.huang@intel.com>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com,
        Zi Yan <ziy@nvidia.com>, Michal Hocko <mhocko@suse.com>,
        Shakeel Butt <shakeelb@google.com>,
        Roman Gushchin <guro@fb.com>
References: <20220518190911.82400-1-hannes@cmpxchg.org>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20220518190911.82400-1-hannes@cmpxchg.org>
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On 5/18/22 12:09, Johannes Weiner wrote:
> However, with NUMA balancing now doing tier promotions, demotion is
> part of the page aging process. Global reclaim demotes the coldest
> toptier pages to secondary memory, where their life continues and from
> which they have a chance to get promoted back. Essentially, tiered
> memory systems have an LRU order that spans multiple nodes.

Thanks for the detailed explanation.  Ultimately, this was just intended
as an optimization to make cgroup reclaim more efficient.  But, I agree
that ordering correctness should trump efficiency.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>