linux-kernel - Re: [PATCH 0/4] [RFC] Migrate Pages in lieu of discard

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Date:   Thu, 17 Oct 2019 14:05:52 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Yang Shi <shy828301@...il.com>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Jonathan Adams <jwadams@...gle.com>,
        "Chen, Tim C" <tim.c.chen@...el.com>
Subject: Re: [PATCH 0/4] [RFC] Migrate Pages in lieu of discard

On 10/17/19 10:20 AM, Yang Shi wrote:
> On Thu, Oct 17, 2019 at 7:26 AM Dave Hansen <dave.hansen@...el.com> wrote:
>> My expectation (and I haven't confirmed this) is that the any memory use
>> is accounted to the owning cgroup, whether it is DRAM or PMEM.  memcg
>> limit reclaim and global reclaim both end up doing migrations and
>> neither should have a net effect on the counters.
> 
> Yes, your expectation is correct. As long as PMEM is a NUMA node, it
> is treated as regular memory by memcg. But, I don't think memcg limit
> reclaim should do migration since limit reclaim is used to reduce
> memory usage, but migration doesn't reduce usage, it just moves memory
> from one node to the other.
> 
> In my implementation, I just skip migration for memcg limit reclaim,
> please see: https://lore.kernel.org/linux-mm/1560468577-101178-7-git-send-email-yang.shi@linux.alibaba.com/

Ahh, got it.  That does make sense.  I might have to steal your
implementation.