linux-kernel - Re: RFC: Memory Tiering Kernel Interfaces (v2)

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Date:   Wed, 25 May 2022 08:33:43 -0700
From:   Wei Xu <weixugc@...gle.com>
To:     Mika Penttilä <mpenttil@...hat.com>
Cc:     Aneesh Kumar K V <aneesh.kumar@...ux.ibm.com>,
        Ying Huang <ying.huang@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Thelen <gthelen@...gle.com>,
        Yang Shi <shy828301@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jagdish Gediya <jvgediya@...ux.ibm.com>,
        Michal Hocko <mhocko@...nel.org>,
        Tim C Chen <tim.c.chen@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Alistair Popple <apopple@...dia.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Feng Tang <feng.tang@...el.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dan Williams <dan.j.williams@...el.com>,
        David Rientjes <rientjes@...gle.com>,
        Linux MM <linux-mm@...ck.org>,
        Brice Goglin <brice.goglin@...il.com>,
        Hesham Almatary <hesham.almatary@...wei.com>
Subject: Re: RFC: Memory Tiering Kernel Interfaces (v2)

On Wed, May 25, 2022 at 4:37 AM Mika Penttilä <mpenttil@...hat.com> wrote:
>
>
>
> On 25.5.2022 13.01, Aneesh Kumar K V wrote:
> > On 5/25/22 2:33 PM, Ying Huang wrote:
> >> On Tue, 2022-05-24 at 22:32 -0700, Wei Xu wrote:
> >>> On Tue, May 24, 2022 at 1:24 AM Ying Huang <ying.huang@...el.com> wrote:
> >>>>
> >>>> On Tue, 2022-05-24 at 00:04 -0700, Wei Xu wrote:
> >>>>> On Thu, May 19, 2022 at 8:06 PM Ying Huang <ying.huang@...el.com>
> >>>>> wrote:
> >>>>>>
> >
> > ...
> >
> >>
> >> OK.  Just to confirm.  Does this mean that we will have fixed device ID,
> >> for example,
> >>
> >> GPU            memtier255
> >> DRAM (with CPU)        memtier0
> >> PMEM            memtier1
> >>
> >> When we add a new memtier, it can be memtier254, or memter2?  The rank
> >> value will determine the real demotion order.
> >>
> >> I think you may need to send v3 to make sure everyone is at the same
> >> page.
> >>
> >
> > What we have implemented which we will send as RFC shortly is below.
> >
> > cd /sys/dekvaneesh@...ntu-guest:~$ cd /sys/devices/system/
> > kvaneesh@...ntu-guest:/sys/devices/system$ pwd
> > /sys/devices/system
> > kvaneesh@...ntu-guest:/sys/devices/system$ ls
> > clockevents  clocksource  container  cpu  edac  memory  memtier  mpic
> > node  power
> > kvaneesh@...ntu-guest:/sys/devices/system$ cd memtier/
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier$ pwd
> > /sys/devices/system/memtier
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier$ ls
> > default_rank  max_rank  memtier1  power  uevent
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier$ cat default_rank
> > 1
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier$ cat max_rank
> > 3
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier$ cd memtier1/
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier/memtier1$ ls
> > nodelist  power  rank  subsystem  uevent
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier/memtier1$ cat nodelist
> > 0-3
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier/memtier1$ cat rank
> > 1
> > kvaneesh@...ntu-guest:/sys/devices/system/memtier/memtier1$ cd
> > ../../node/node1/
> > kvaneesh@...ntu-guest:/sys/devices/system/node/node1$ cat memtier
> > 1
> > kvaneesh@...ntu-guest:/sys/devices/system/node/node1$
> > root@...ntu-guest:/sys/devices/system/node/node1# echo 0 > memtier
> > root@...ntu-guest:/sys/devices/system/node/node1# cat memtier
> > 0
> > root@...ntu-guest:/sys/devices/system/node/node1# cd ../../memtier/
> > root@...ntu-guest:/sys/devices/system/memtier# ls
> > default_rank  max_rank  memtier0  memtier1  power  uevent
> > root@...ntu-guest:/sys/devices/system/memtier# cd memtier0/
> > root@...ntu-guest:/sys/devices/system/memtier/memtier0# cat nodelist
> > 1
> > root@...ntu-guest:/sys/devices/system/memtier/memtier0# cat rank
> > 0
> > root@...ntu-guest:/sys/devices/system/memtier/memtier0# echo 4 > rank
> > bash: rank: Permission denied
> > root@...ntu-guest:/sys/devices/system/memtier/memtier0#
> >
>
> Just to confirm, unlike today's demotion code, the demotion target
> allocation is planned to honor mempolicies?

Yes, though there will be some limitations in the beginning,
specifically for per-thread mempolicy.

>
> --Mika
>
>