linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Yang Shi <yang.shi@linux.alibaba.com>
To: Keith Busch <kbusch@kernel.org>
Cc: mhocko@suse.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, fengguang.wu@intel.com,
	fan.du@intel.com, ying.huang@intel.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 06/10] mm: vmscan: demote anon DRAM pages to PMEM node
Date: Tue, 26 Mar 2019 20:41:15 -0700	[thread overview]
Message-ID: <39d8fb56-df60-9382-9b47-59081d823c3c@linux.alibaba.com> (raw)
In-Reply-To: <20190327003541.GE4328@localhost.localdomain>



On 3/26/19 5:35 PM, Keith Busch wrote:
> On Mon, Mar 25, 2019 at 12:49:21PM -0700, Yang Shi wrote:
>> On 3/24/19 3:20 PM, Keith Busch wrote:
>>> How do these pages eventually get to swap when migration fails? Looks
>>> like that's skipped.
>> Yes, they will be just put back to LRU. Actually, I don't expect it would be
>> very often to have migration fail at this stage (but I have no test data to
>> support this hypothesis) since the pages have been isolated from LRU, so
>> other reclaim path should not find them anymore.
>>
>> If it is locked by someone else right before migration, it is likely
>> referenced again, so putting back to LRU sounds not bad.
>>
>> A potential improvement is to have sync migration for kswapd.
> Well, it's not that migration fails only if the page is recently
> referenced. Migration would fail if there isn't available memory in
> the migration node, so this implementation carries an expectation that
> migration nodes have higher free capacity than source nodes. And since
> your attempting THP's without ever splitting them, that also requires
> lower fragmentation for a successful migration.

Yes, it is possible. However, migrate_pages() already has logic to 
handle such case. If the target node has not enough space for migrating 
THP in a whole, it would split THP then retry with base pages.

Swapping THP has been optimized to swap in a whole too. It would try to 
add THP into swap cache in a whole, split THP if the attempt fails, then 
add base pages into swap cache.

So, I think we can leave this to migrate_pages() without splitting in 
advance all the time.

Thanks,
Yang

>
> Applications, however, may allocate and pin pages directly out of that
> migration node to the point it does not have so much free capacity or
> physical continuity, so we probably shouldn't assume it's the only way
> to reclaim pages.


  reply	other threads:[~2019-03-27  3:41 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 [this message]
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
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

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=39d8fb56-df60-9382-9b47-59081d823c3c@linux.alibaba.com \
    --to=yang.shi@linux.alibaba.com \
    --cc=akpm@linux-foundation.org \
    --cc=dan.j.williams@intel.com \
    --cc=dave.hansen@intel.com \
    --cc=fan.du@intel.com \
    --cc=fengguang.wu@intel.com \
    --cc=hannes@cmpxchg.org \
    --cc=kbusch@kernel.org \
    --cc=keith.busch@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mgorman@techsingularity.net \
    --cc=mhocko@suse.com \
    --cc=riel@surriel.com \
    --cc=ying.huang@intel.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).