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From:   "Huang, Ying" <ying.huang@intel.com>
To:     Michal Hocko <mhocko@suse.com>
Cc:     David Hildenbrand <david@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Arjan Van De Ven <arjan@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Vlastimil Babka <vbabka@suse.cz>,
        Johannes Weiner <jweiner@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Matthew Wilcox <willy@infradead.org>
Subject: Re: [RFC 0/6] mm: improve page allocator scalability via splitting
 zones
References: <20230511065607.37407-1-ying.huang@intel.com>
        <ZF0ET82ajDbFrIw/@dhcp22.suse.cz>
        <87r0rm8die.fsf@yhuang6-desk2.ccr.corp.intel.com>
        <ZGIUEqhSydAdvRFN@dhcp22.suse.cz>
        <87jzx87h1d.fsf@yhuang6-desk2.ccr.corp.intel.com>
        <3d77ca46-6256-7996-b0f5-67c414d2a8dc@redhat.com>
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Date:   Mon, 29 May 2023 09:13:37 +0800
In-Reply-To: <ZG4Db1QSE1LZXEEP@dhcp22.suse.cz> (Michal Hocko's message of
        "Wed, 24 May 2023 14:30:39 +0200")
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Michal Hocko <mhocko@suse.com> writes:

> [Sorry for late reply, conferencing last 2 weeks and now catching up]

Never mind.  And my reply is late too for sickness.

> On Tue 16-05-23 12:30:21, David Hildenbrand wrote:
> [...]
>> > And auto-tuning doesn't sound easy.  Do you have some idea of how to do
>> > that?
>> 
>> If we could avoid instantiating more zones and rather improve existing
>> mechanisms (PCP), that would be much more preferred IMHO. I'm sure it's not
>> easy, but that shouldn't stop us from trying ;)
>
> Absolutely agreed. Increasing the zone number sounds like a hack to me
> TBH. It seems like an easier way but it allows more subtle problems
> later on. E.g. hard to predict per-zone memory consumption and memory
> reclaim disbalances.

At least, we all think that improving PCP is something deserved to be
done.  I will do some experiment on that and return to you (after some
time).

Best Regards,
Huang, Ying