Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 31 Oct 2022 09:40:15 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     "Huang, Ying" <ying.huang@intel.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
Message-ID: <Y1+J7+1V1nJXF+3b@dhcp22.suse.cz>
References: <Y1j7tsj5M0Md/+Er@dhcp22.suse.cz>
 <Y1kl8VbPE0RYdyEB@feng-clx>
 <Y1lZV6qHp3gIINGc@dhcp22.suse.cz>
 <87wn8lkbk5.fsf@yhuang6-desk2.ccr.corp.intel.com>
 <Y1ou5DGHrEsKnhri@dhcp22.suse.cz>
 <87o7txk963.fsf@yhuang6-desk2.ccr.corp.intel.com>
 <Y1o63SWD2KmQkT3v@dhcp22.suse.cz>
 <87fsf9k3yg.fsf@yhuang6-desk2.ccr.corp.intel.com>
 <Y1p5vaN1AWhpNWZx@dhcp22.suse.cz>
 <87bkpwkg24.fsf@yhuang6-desk2.ccr.corp.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87bkpwkg24.fsf@yhuang6-desk2.ccr.corp.intel.com>
Precedence: bulk

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.
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.

-- 
Michal Hocko
SUSE Labs