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

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Date:   Wed, 25 May 2022 15:31:13 +0530
From:   Aneesh Kumar K V <aneesh.kumar@...ux.ibm.com>
To:     Ying Huang <ying.huang@...el.com>, Wei Xu <weixugc@...gle.com>
Cc:     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 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#