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

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Date:   Wed, 25 May 2022 14:36:59 +0300
From:   Mika Penttilä <mpenttil@...hat.com>
To:     Aneesh Kumar K V <aneesh.kumar@...ux.ibm.com>,
        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 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?


--Mika