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From: Michal Hocko <mhocko@kernel.org>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Rik van Riel <riel@surriel.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Keith Busch <keith.busch@intel.com>,
	Fengguang Wu <fengguang.wu@intel.com>,
	"Du, Fan" <fan.du@intel.com>,
	"Huang, Ying" <ying.huang@intel.com>,
	Linux MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node
Date: Thu, 28 Mar 2019 21:40:20 +0100	[thread overview]
Message-ID: <20190328204020.GD7155@dhcp22.suse.cz> (raw)
In-Reply-To: <5934ed42-c512-a4c7-cbed-9062065bf276@linux.alibaba.com>

On Thu 28-03-19 12:40:14, Yang Shi wrote:
> 
> 
> On 3/28/19 12:12 PM, Michal Hocko wrote:
> > On Thu 28-03-19 11:58:57, Yang Shi wrote:
> > > 
> > > On 3/27/19 11:58 PM, Michal Hocko wrote:
> > > > On Wed 27-03-19 19:09:10, Yang Shi wrote:
> > > > > One question, when doing demote and promote we need define a path, for
> > > > > example, DRAM <-> PMEM (assume two tier memory). When determining what nodes
> > > > > are "DRAM" nodes, does it make sense to assume the nodes with both cpu and
> > > > > memory are DRAM nodes since PMEM nodes are typically cpuless nodes?
> > > > Do we really have to special case this for PMEM? Why cannot we simply go
> > > > in the zonelist order? In other words why cannot we use the same logic
> > > > for a larger NUMA machine and instead of swapping simply fallback to a
> > > > less contended NUMA node? It can be a regular DRAM, PMEM or whatever
> > > > other type of memory node.
> > > Thanks for the suggestion. It makes sense. However, if we don't specialize a
> > > pmem node, its fallback node may be a DRAM node, then the memory reclaim may
> > > move the inactive page to the DRAM node, it sounds not make too much sense
> > > since memory reclaim would prefer to move downwards (DRAM -> PMEM -> Disk).
> > There are certainly many details to sort out. One thing is how to handle
> > cpuless nodes (e.g. PMEM). Those shouldn't get any direct allocations
> > without an explicit binding, right? My first naive idea would be to only
> 
> Wait a minute. I thought we were arguing about the default allocation node
> mask yesterday. And, the conclusion is PMEM node should not be excluded from
> the node mask. PMEM nodes are cpuless nodes. I think I should replace all
> "PMEM node" to "cpuless node" in the cover letter and commit logs to make it
> explicitly.

No, this is not about the default allocation mask at all. Your
allocations start from a local/mempolicy node. CPUless nodes thus cannot be a
primary node so it will always be only in a fallback zonelist without an
explicit binding.

-- 
Michal Hocko
SUSE Labs


  reply	other threads:[~2019-03-28 20:40 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-23  4:44 [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node Yang Shi
2019-03-23  4:44 ` [PATCH 01/10] mm: control memory placement by nodemask for two tier main memory Yang Shi
2019-03-23 17:21   ` Dan Williams
2019-03-25 19:28     ` Yang Shi
2019-03-25 23:18       ` Dan Williams
2019-03-25 23:36         ` Yang Shi
2019-03-25 23:42           ` Dan Williams
2019-03-23  4:44 ` [PATCH 02/10] mm: mempolicy: introduce MPOL_HYBRID policy Yang Shi
2019-03-23  4:44 ` [PATCH 03/10] mm: mempolicy: promote page to DRAM for MPOL_HYBRID Yang Shi
2019-03-23  4:44 ` [PATCH 04/10] mm: numa: promote pages to DRAM when it is accessed twice Yang Shi
2019-03-29  0:31   ` kbuild test robot
2019-03-23  4:44 ` [PATCH 05/10] mm: page_alloc: make find_next_best_node could skip DRAM node Yang Shi
2019-03-23  4:44 ` [PATCH 06/10] mm: vmscan: demote anon DRAM pages to PMEM node Yang Shi
2019-03-23  6:03   ` Zi Yan
2019-03-25 21:49     ` Yang Shi
2019-03-24 22:20   ` Keith Busch
2019-03-25 19:49     ` Yang Shi
2019-03-27  0:35       ` Keith Busch
2019-03-27  3:41         ` Yang Shi
2019-03-27 13:08           ` Keith Busch
2019-03-27 17:00             ` Zi Yan
2019-03-27 17:05               ` Dave Hansen
2019-03-27 17:48                 ` Zi Yan
2019-03-27 18:00                   ` Dave Hansen
2019-03-27 20:37                     ` Zi Yan
2019-03-27 20:42                       ` Dave Hansen
2019-03-28 21:59             ` Yang Shi
2019-03-28 22:45               ` Keith Busch
2019-03-23  4:44 ` [PATCH 07/10] mm: vmscan: add page demotion counter Yang Shi
2019-03-23  4:44 ` [PATCH 08/10] mm: numa: add page promotion counter Yang Shi
2019-03-23  4:44 ` [PATCH 09/10] doc: add description for MPOL_HYBRID mode Yang Shi
2019-03-23  4:44 ` [PATCH 10/10] doc: elaborate the PMEM allocation rule Yang Shi
2019-03-25 16:15 ` [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node Brice Goglin
2019-03-25 16:56   ` Dan Williams
2019-03-25 17:45     ` Brice Goglin
2019-03-25 19:29       ` Dan Williams
2019-03-25 23:09         ` Brice Goglin
2019-03-25 23:37           ` Dan Williams
2019-03-26 12:19             ` Jonathan Cameron
2019-03-25 20:04   ` Yang Shi
2019-03-26 13:58 ` Michal Hocko
2019-03-26 18:33   ` Yang Shi
2019-03-26 18:37     ` Michal Hocko
2019-03-27  2:58       ` Yang Shi
2019-03-27  9:01         ` Michal Hocko
2019-03-27 17:34           ` Dan Williams
2019-03-27 18:59             ` Yang Shi
2019-03-27 20:09               ` Michal Hocko
2019-03-28  2:09                 ` Yang Shi
2019-03-28  6:58                   ` Michal Hocko
2019-03-28 18:58                     ` Yang Shi
2019-03-28 19:12                       ` Michal Hocko
2019-03-28 19:40                         ` Yang Shi
2019-03-28 20:40                           ` Michal Hocko [this message]
2019-03-28  8:21                   ` Dan Williams
2019-03-27 20:14               ` Dave Hansen
2019-03-27 20:35             ` Matthew Wilcox
2019-03-27 20:40               ` Dave Hansen

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