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Message-ID: <6e94b7e2a6192e4cacba1db3676b5b5cf9b98eac.camel@intel.com>
Subject: Re: [PATCH v5 9/9] mm/demotion: Update node_is_toptier to work with
 memory tiers
From:   Ying Huang <ying.huang@intel.com>
To:     "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        linux-mm@kvack.org, akpm@linux-foundation.org
Cc:     Wei Xu <weixugc@google.com>, Greg Thelen <gthelen@google.com>,
        Yang Shi <shy828301@gmail.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Tim C Chen <tim.c.chen@intel.com>,
        Brice Goglin <brice.goglin@gmail.com>,
        Michal Hocko <mhocko@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Hesham Almatary <hesham.almatary@huawei.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Alistair Popple <apopple@nvidia.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Feng Tang <feng.tang@intel.com>,
        Jagdish Gediya <jvgediya@linux.ibm.com>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        David Rientjes <rientjes@google.com>
Date:   Mon, 06 Jun 2022 11:11:23 +0800
In-Reply-To: <20220603134237.131362-10-aneesh.kumar@linux.ibm.com>
References: <20220603134237.131362-1-aneesh.kumar@linux.ibm.com>
         <20220603134237.131362-10-aneesh.kumar@linux.ibm.com>
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On Fri, 2022-06-03 at 19:12 +0530, Aneesh Kumar K.V wrote:
> With memory tiers support we can have memory on NUMA nodes
> in the top tier from which we want to avoid promotion tracking NUMA
> faults. Update node_is_toptier to work with memory tiers. To
> avoid taking locks, a nodemask is maintained for all demotion
> targets. All NUMA nodes are by default top tier nodes and as
> we add new lower memory tiers NUMA nodes get added to the
> demotion targets thereby moving them out of the top tier.

Check the usage of node_is_toptier(),

- migrate_misplaced_page()
  node_is_toptier() is used to check whether migration is a promotion. 
We can avoid to use it.  Just compare the rank of the nodes.

- change_pte_range() and change_huge_pmd()
  node_is_toptier() is used to avoid scanning fast memory (DRAM) pages
for promotion.  So I think we should change the name to node_is_fast()
as follows,

static inline bool node_is_fast(int node)
{
	return NODE_DATA(node)->mt_rank >= MEMORY_RANK_DRAM;
}

And, as above, I suggest to add memory tier ID and rank to struct
pglist_data directly.

Best Regards,
Huang, Ying