From: Zi Yan <ziy@nvidia.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
<mgorman@techsingularity.net>, <riel@surriel.com>,
<hannes@cmpxchg.org>, <akpm@linux-foundation.org>,
<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: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node
Date: Tue, 16 Apr 2019 11:33:48 -0400 [thread overview]
Message-ID: <960F3918-7D2C-463C-A911-9B62CD7E5D83@nvidia.com> (raw)
In-Reply-To: <b9b40585-cb59-3d42-bcf8-e59bff77c663@intel.com>
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On 16 Apr 2019, at 10:30, Dave Hansen wrote:
> On 4/16/19 12:47 AM, Michal Hocko wrote:
>> You definitely have to follow policy. You cannot demote to a node which
>> is outside of the cpuset/mempolicy because you are breaking contract
>> expected by the userspace. That implies doing a rmap walk.
>
> What *is* the contract with userspace, anyway? :)
>
> Obviously, the preferred policy doesn't have any strict contract.
>
> The strict binding has a bit more of a contract, but it doesn't prevent
> swapping. Strict binding also doesn't keep another app from moving the
> memory.
>
> We have a reasonable argument that demotion is better than swapping.
> So, we could say that even if a VMA has a strict NUMA policy, demoting
> pages mapped there pages still beats swapping them or tossing the page
> cache. It's doing them a favor to demote them.
I just wonder whether page migration is always better than swapping,
since SSD write throughput keeps improving but page migration throughput
is still low. For example, my machine has a SSD with 2GB/s writing throughput
but the throughput of 4KB page migration is less than 1GB/s, why do we
want to use page migration for demotion instead of swapping?
--
Best Regards,
Yan Zi
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next prev parent reply other threads:[~2019-04-16 15:33 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 [this message]
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
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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