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[79.242.62.176]) by smtp.gmail.com with ESMTPSA id c1sm2569703wrx.89.2021.04.22.02.37.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Apr 2021 02:37:07 -0700 (PDT) To: "lipeifeng@oppo.com" , Vlastimil Babka , peifengl55 , schwidefsky , "heiko.carstens" Cc: linux-s390 , linux-kernel , linux-mm , zhangshiming , guoweichao , zhouhuacai References: <20210414023803.937-1-lipeifeng@oppo.com> <2021041910374593320011@oppo.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [RFC] mm: support multi_freearea to the reduction of external fragmentation Message-ID: <0585db50-e8d5-e6d8-9d41-fc398f292d91@redhat.com> Date: Thu, 22 Apr 2021 11:37:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <2021041910374593320011@oppo.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Stat-Signature: z5zoq14jxqbxtrj9n1cyqug9iussacp4 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E014380192C7 Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf16; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619084229-207074 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 19.04.21 04:37, lipeifeng@oppo.com wrote: > Hi Vlastimil Babka: > Thank you very much indeed for your advice. >=20 >=20 > Hi Vlastimil Babka, schwidefsky,heiko.carstens: >=20 > It is a temporary patch to consult experts: > Is it possible to merge the optimization idea and the implementation > method=C2=A0to the baseline? Well, we cannot really say that :) History taught that merging large and invasive buddy changes is a=20 tedious task, can take a long time, and can fail even after a lot of=20 discussions and patch series. Further, usually there has to be a very compelling reason to merge=20 large, invasive buddy changes (read: not only optimize very specific=20 scenarios); otherwise there will just push back because the invasive=20 changes might introduce additional problems or degrade other special=20 cases or even the general case. Last but not least, there have to be more benchmarks and test cases that=20 proof that other workload won't be degraded to a degree that people=20 care; as one example, this includes runtime overhead when=20 allocating/freeing pages. What usually works best is improving the code in small steps, doing=20 minor adjustments but moving into the desired direction. --=20 Thanks, David / dhildenb