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

[Dave Hansen]

On 10/17/19 10:20 AM, Yang Shi wrote:
> On Thu, Oct 17, 2019 at 7:26 AM Dave Hansen <dave.hansen@xxxxxxxxx> 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@xxxxxxxxxxxxxxxxx/

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