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From:   "Huang, Ying" <ying.huang@intel.com>
To:     Michal Hocko <mhocko@suse.com>
Cc:     Feng Tang <feng.tang@intel.com>,
        Aneesh Kumar K V <aneesh.kumar@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Tejun Heo <tj@kernel.org>, Zefan Li <lizefan.x@bytedance.com>,
        Waiman Long <longman@redhat.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        "Chen, Tim C" <tim.c.chen@intel.com>,
        "Yin, Fengwei" <fengwei.yin@intel.com>
Subject: Re: [PATCH] mm/vmscan: respect cpuset policy during page demotion
References: <Y1j7tsj5M0Md/+Er@dhcp22.suse.cz> <Y1kl8VbPE0RYdyEB@feng-clx>
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        <87o7txk963.fsf@yhuang6-desk2.ccr.corp.intel.com>
        <Y1o63SWD2KmQkT3v@dhcp22.suse.cz>
        <87fsf9k3yg.fsf@yhuang6-desk2.ccr.corp.intel.com>
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Date:   Mon, 31 Oct 2022 16:51:11 +0800
In-Reply-To: <Y1+J7+1V1nJXF+3b@dhcp22.suse.cz> (Michal Hocko's message of
        "Mon, 31 Oct 2022 09:40:15 +0100")
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Michal Hocko <mhocko@suse.com> writes:

> On Fri 28-10-22 07:22:27, Huang, Ying wrote:
>> Michal Hocko <mhocko@suse.com> writes:
>> 
>> > On Thu 27-10-22 17:31:35, Huang, Ying wrote:
> [...]
>> >> I think that it's possible for different processes have different
>> >> requirements.
>> >> 
>> >> - Some processes don't care about where the memory is placed, prefer
>> >>   local, then fall back to remote if no free space.
>> >> 
>> >> - Some processes want to avoid cross-socket traffic, bind to nodes of
>> >>   local socket.
>> >> 
>> >> - Some processes want to avoid to use slow memory, bind to fast memory
>> >>   node only.
>> >
>> > Yes, I do understand that. Do you have any specific examples in mind?
>> > [...]
>> 
>> Sorry, I don't have specific examples.
>
> OK, then let's stop any complicated solution right here then. Let's
> start simple with a per-mm flag to disable demotion of an address
> space.

I'm not a big fan of per-mm flag.  Because we don't have users for that
too and it needs to add ABI too.

> Should there ever be a real demand for a more fine grained solution
> let's go further but I do not think we want a half baked solution
> without real usecases.

I'm OK to ignore per-task (and missing per-process) memory policy
support for now.

Best Regards,
Huang, Ying