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From: Keith Busch <keith.busch@intel.com>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	Dave Hansen <dave.hansen@intel.com>,
	mgorman@techsingularity.net, riel@surriel.com,
	hannes@cmpxchg.org, akpm@linux-foundation.org,
	dan.j.williams@intel.com, fengguang.wu@intel.com,
	fan.du@intel.com, ying.huang@intel.com, ziy@nvidia.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node
Date: Wed, 17 Apr 2019 11:29:33 -0600	[thread overview]
Message-ID: <20190417172932.GA6176@localhost.localdomain> (raw)
In-Reply-To: <fcb30853-8039-8154-7ae0-706930642576@linux.alibaba.com>

On Wed, Apr 17, 2019 at 10:26:05AM -0700, Yang Shi wrote:
> On 4/17/19 9:39 AM, Michal Hocko wrote:
> > On Wed 17-04-19 09:37:39, Keith Busch wrote:
> > > On Wed, Apr 17, 2019 at 05:39:23PM +0200, Michal Hocko wrote:
> > > > On Wed 17-04-19 09:23:46, Keith Busch wrote:
> > > > > On Wed, Apr 17, 2019 at 11:23:18AM +0200, Michal Hocko wrote:
> > > > > > On Tue 16-04-19 14:22:33, Dave Hansen wrote:
> > > > > > > Keith Busch had a set of patches to let you specify the demotion order
> > > > > > > via sysfs for fun.  The rules we came up with were:
> > > > > > I am not a fan of any sysfs "fun"
> > > > > I'm hung up on the user facing interface, but there should be some way a
> > > > > user decides if a memory node is or is not a migrate target, right?
> > > > Why? Or to put it differently, why do we have to start with a user
> > > > interface at this stage when we actually barely have any real usecases
> > > > out there?
> > > The use case is an alternative to swap, right? The user has to decide
> > > which storage is the swap target, so operating in the same spirit.
> > I do not follow. If you use rebalancing you can still deplete the memory
> > and end up in a swap storage. If you want to reclaim/swap rather than
> > rebalance then you do not enable rebalancing (by node_reclaim or similar
> > mechanism).
> 
> I'm a little bit confused. Do you mean just do *not* do reclaim/swap in
> rebalancing mode? If rebalancing is on, then node_reclaim just move the
> pages around nodes, then kswapd or direct reclaim would take care of swap?
> 
> If so the node reclaim on PMEM node may rebalance the pages to DRAM node?
> Should this be allowed?
> 
> I think both I and Keith was supposed to treat PMEM as a tier in the reclaim
> hierarchy. The reclaim should push inactive pages down to PMEM, then swap.
> So, PMEM is kind of a "terminal" node. So, he introduced sysfs defined
> target node, I introduced N_CPU_MEM.

Yeah, I think Yang and I view "demotion" as a separate feature from
numa rebalancing.


  reply	other threads:[~2019-04-17 17:35 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-11  3:56 [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node Yang Shi
2019-04-11  3:56 ` [v2 PATCH 1/9] mm: define N_CPU_MEM node states Yang Shi
2019-04-11  3:56 ` [v2 PATCH 2/9] mm: page_alloc: make find_next_best_node find return cpuless node Yang Shi
2019-04-11  3:56 ` [v2 PATCH 3/9] mm: numa: promote pages to DRAM when it gets accessed twice Yang Shi
2019-04-11  3:56 ` [v2 PATCH 4/9] mm: migrate: make migrate_pages() return nr_succeeded Yang Shi
2019-04-11  3:56 ` [v2 PATCH 5/9] mm: vmscan: demote anon DRAM pages to PMEM node Yang Shi
2019-04-11 14:31   ` Dave Hansen
2019-04-15 22:10     ` Yang Shi
2019-04-15 22:14       ` Dave Hansen
2019-04-15 22:26         ` Yang Shi
2019-04-11  3:56 ` [v2 PATCH 6/9] mm: vmscan: don't demote for memcg reclaim Yang Shi
2019-04-11  3:56 ` [v2 PATCH 7/9] mm: vmscan: check if the demote target node is contended or not Yang Shi
2019-04-11 16:06   ` Dave Hansen
2019-04-15 22:06     ` Yang Shi
2019-04-15 22:13       ` Dave Hansen
2019-04-15 22:23         ` Yang Shi
2019-04-11  3:56 ` [v2 PATCH 8/9] mm: vmscan: add page demotion counter Yang Shi
2019-04-11  3:56 ` [v2 PATCH 9/9] mm: numa: add page promotion counter Yang Shi
2019-04-11 14:28 ` [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node Dave Hansen
2019-04-12  8:47 ` Michal Hocko
2019-04-16  0:09   ` Yang Shi
2019-04-16  7:47     ` Michal Hocko
2019-04-16 14:30       ` Dave Hansen
2019-04-16 14:39         ` Michal Hocko
2019-04-16 15:46           ` Dave Hansen
2019-04-16 18:34             ` Michal Hocko
2019-04-16 15:33         ` Zi Yan
2019-04-16 15:55           ` Dave Hansen
2019-04-16 16:12             ` Zi Yan
2019-04-16 19:19       ` Yang Shi
2019-04-16 21:22         ` Dave Hansen
2019-04-16 21:59           ` Yang Shi
2019-04-16 23:04             ` Dave Hansen
2019-04-16 23:17               ` Yang Shi
2019-04-17 15:13                 ` Keith Busch
2019-04-17  9:23           ` Michal Hocko
2019-04-17 15:23             ` Keith Busch
2019-04-17 15:39               ` Michal Hocko
2019-04-17 15:37                 ` Keith Busch
2019-04-17 16:39                   ` Michal Hocko
2019-04-17 17:26                     ` Yang Shi
2019-04-17 17:29                       ` Keith Busch [this message]
2019-04-17 17:51                       ` Michal Hocko
2019-04-18 16:24                         ` Yang Shi
2019-04-17 17:13             ` Dave Hansen
2019-04-17 17:57               ` Michal Hocko
2019-04-18 18:16               ` Keith Busch
2019-04-18 19:23                 ` Yang Shi
2019-04-18 21:07                   ` Zi Yan
2019-04-16 23:18         ` Yang Shi
2019-04-17  9:17         ` Michal Hocko
2019-05-01  6:43           ` Fengguang Wu
2019-04-17 20:43         ` Yang Shi
2019-04-18  9:02           ` Michal Hocko
2019-05-01  5:20             ` Fengguang Wu

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