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.
next prev parent 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
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