From: Fengguang Wu <fengguang.wu@intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Yang Shi <yang.shi@linux.alibaba.com>,
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, 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, 1 May 2019 14:43:36 +0800 [thread overview]
Message-ID: <20190501064336.jktcqkvz27ihpqh3@wfg-t540p.sh.intel.com> (raw)
In-Reply-To: <20190417091748.GF655@dhcp22.suse.cz>
On Wed, Apr 17, 2019 at 11:17:48AM +0200, Michal Hocko wrote:
>On Tue 16-04-19 12:19:21, Yang Shi wrote:
>>
>>
>> On 4/16/19 12:47 AM, Michal Hocko wrote:
>[...]
>> > Why cannot we simply demote in the proximity order? Why do you make
>> > cpuless nodes so special? If other close nodes are vacant then just use
>> > them.
>>
>> We could. But, this raises another question, would we prefer to just demote
>> to the next fallback node (just try once), if it is contended, then just
>> swap (i.e. DRAM0 -> PMEM0 -> Swap); or would we prefer to try all the nodes
>> in the fallback order to find the first less contended one (i.e. DRAM0 ->
>> PMEM0 -> DRAM1 -> PMEM1 -> Swap)?
>
>I would go with the later. Why, because it is more natural. Because that
>is the natural allocation path so I do not see why this shouldn't be the
>natural demotion path.
"Demotion" should be more performance wise by "demoting to the
next-level (cheaper/slower) memory". Otherwise something like this
may happen.
DRAM0 pressured => demote cold pages to DRAM1
DRAM1 pressured => demote cold pages to DRAM0
Kind of DRAM0/DRAM1 exchanged a fraction of the demoted cold pages,
which looks not helpful for overall system performance.
Over time, it's even possible some cold pages get "demoted" in path
DRAM0=>DRAM1=>DRAM0=>DRAM1=>...
Thanks,
Fengguang
next prev parent reply other threads:[~2019-05-01 6:45 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
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 [this message]
2019-04-17 20:43 ` Yang Shi
2019-04-18 9:02 ` Michal Hocko
2019-05-01 5:20 ` Fengguang Wu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190501064336.jktcqkvz27ihpqh3@wfg-t540p.sh.intel.com \
--to=fengguang.wu@intel.com \
--cc=akpm@linux-foundation.org \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@intel.com \
--cc=fan.du@intel.com \
--cc=hannes@cmpxchg.org \
--cc=keith.busch@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=riel@surriel.com \
--cc=yang.shi@linux.alibaba.com \
--cc=ying.huang@intel.com \
--cc=ziy@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).