Re: [PATCH 0/2] Page migration via Swap V2: Overview

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

Hi,
Christoph Lameter wrote:
> The patchset consists of two patches:
> 
> 1. Page eviction patch
> 
> Modifies mm/vmscan.c to add functions to isolate pages from the LRU lists,
> swapout lists of pages and return pages to the LRU lists.
> 
> 2. MPOL_MF_MOVE flag for memory policies.
> 
> This implements MPOL_MF_MOVE in addition to MPOL_MF_STRICT. MPOL_MF_STRICT
> allows the checking if all pages in a memory area obey the memory policies.
> MPOL_MF_MOVE will evict all pages that do not conform to the memory policy.
> The system will allocate pages conforming to the policy on swap in.
> 

Because sys_mbind() acquires mm->mmap_sem, once page is unmapped,
all accesses to the page are blocked.

So, even if the range contains hot pages, there will not be
hard-to-be-swapped-out pages. right ?

sys_mbind() can aquire mm->mmap_sem for migrating *a process's page*,
but memory-hotplug cannot aquire the lock for migrating a chunk of pages.

I think we'll need radix_tree_replace for migating arbitrary chunk of pages, anyway.

Thanks,
-- Kame

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