From: Michal Hocko <mhocko@kernel.org>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: mgorman@techsingularity.net, riel@surriel.com,
hannes@cmpxchg.org, akpm@linux-foundation.org,
dave.hansen@intel.com, keith.busch@intel.com,
dan.j.williams@intel.com, fengguang.wu@intel.com,
fan.du@intel.com, ying.huang@intel.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node
Date: Wed, 27 Mar 2019 10:01:00 +0100 [thread overview]
Message-ID: <20190327090100.GD11927@dhcp22.suse.cz> (raw)
In-Reply-To: <f08fb981-d129-3357-e93a-a6b233aa9891@linux.alibaba.com>
On Tue 26-03-19 19:58:56, Yang Shi wrote:
>
>
> On 3/26/19 11:37 AM, Michal Hocko wrote:
> > On Tue 26-03-19 11:33:17, Yang Shi wrote:
> > >
> > > On 3/26/19 6:58 AM, Michal Hocko wrote:
> > > > On Sat 23-03-19 12:44:25, Yang Shi wrote:
> > > > > With Dave Hansen's patches merged into Linus's tree
> > > > >
> > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c221c0b0308fd01d9fb33a16f64d2fd95f8830a4
> > > > >
> > > > > PMEM could be hot plugged as NUMA node now. But, how to use PMEM as NUMA node
> > > > > effectively and efficiently is still a question.
> > > > >
> > > > > There have been a couple of proposals posted on the mailing list [1] [2].
> > > > >
> > > > > The patchset is aimed to try a different approach from this proposal [1]
> > > > > to use PMEM as NUMA nodes.
> > > > >
> > > > > The approach is designed to follow the below principles:
> > > > >
> > > > > 1. Use PMEM as normal NUMA node, no special gfp flag, zone, zonelist, etc.
> > > > >
> > > > > 2. DRAM first/by default. No surprise to existing applications and default
> > > > > running. PMEM will not be allocated unless its node is specified explicitly
> > > > > by NUMA policy. Some applications may be not very sensitive to memory latency,
> > > > > so they could be placed on PMEM nodes then have hot pages promote to DRAM
> > > > > gradually.
> > > > Why are you pushing yourself into the corner right at the beginning? If
> > > > the PMEM is exported as a regular NUMA node then the only difference
> > > > should be performance characteristics (module durability which shouldn't
> > > > play any role in this particular case, right?). Applications which are
> > > > already sensitive to memory access should better use proper binding already.
> > > > Some NUMA topologies might have quite a large interconnect penalties
> > > > already. So this doesn't sound like an argument to me, TBH.
> > > The major rationale behind this is we assume the most applications should be
> > > sensitive to memory access, particularly for meeting the SLA. The
> > > applications run on the machine may be agnostic to us, they may be sensitive
> > > or non-sensitive. But, assuming they are sensitive to memory access sounds
> > > safer from SLA point of view. Then the "cold" pages could be demoted to PMEM
> > > nodes by kernel's memory reclaim or other tools without impairing the SLA.
> > >
> > > If the applications are not sensitive to memory access, they could be bound
> > > to PMEM or allowed to use PMEM (nice to have allocation on DRAM) explicitly,
> > > then the "hot" pages could be promoted to DRAM.
> > Again, how is this different from NUMA in general?
>
> It is still NUMA, users still can see all the NUMA nodes.
No, Linux NUMA implementation makes all numa nodes available by default
and provides an API to opt-in for more fine tuning. What you are
suggesting goes against that semantic and I am asking why. How is pmem
NUMA node any different from any any other distant node in principle?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-03-27 9:01 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 [this message]
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
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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