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[2003:d8:2f38:2400:62f4:c5fa:ba13:ac32]) by smtp.gmail.com with ESMTPSA id g5sm3841603wrq.30.2021.04.27.05.46.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Apr 2021 05:46:06 -0700 (PDT) To: "lipeifeng@oppo.com" , Vlastimil Babka , peifengl55 , schwidefsky , "heiko.carstens" , zhangshiming , zhouhuacai , guoweichao , guojian Cc: linux-s390 , linux-kernel , linux-mm References: <20210414023803.937-1-lipeifeng@oppo.com> <2021042611194631963076@oppo.com> <7dcc87f5-9ae5-613a-0cf4-820334592b90@redhat.com> <20210426181947189100132@oppo.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [RFC] mm: support multi_freearea to the reduction of external fragmentation Message-ID: <9808e36a-9e4e-d1e2-da49-beb567681a8b@redhat.com> Date: Tue, 27 Apr 2021 14:46:06 +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: <20210426181947189100132@oppo.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.04.21 12:19, lipeifeng@oppo.com wrote: > Hi David Hildenbrand ： > > >> And you don't mention what the baseline configuration was. For example, > >> how was compaction configured? > >> Just to clarify, what is monkey? > >> Monkey HTTP server? MonkeyTest disk benchmark? UI/Application Exerciser > >> Monkey? > ------------------------------------------------------------------------------------- > I am sorry that i didn't  give a clear explanation about Monkey. > It meant  "UI/Application Exerciser Monkey" from google. > > Excuse me, let me introduce our test: > Thanks for more details on the test. > 1. record COMPACT_STALL > We tested the patch on linux-4.4/linux-4.9/linux-4.14/linux-4.19 and the > results shows that the patch is effective in reducing COMPACTSTALL. >     - monkey for 12 hours. >     - record COMPACTSTALL after test. > > Test-result: reduced COMPACTSTALL by 95.6% with the patch. > (the machine with 4 gigabytes of physical memery and in linux-4.19.) > --------------------------------- >                      |   COMPACTSTALL > --------------------------------- >    ori              |     2189 > --------------------------------- > optimization |      95 > --------------------------------- > > I fully agree with the value of compaction, but compaction also bring cpu > consumption and will increase the time of alloc_stall. So if we can let more > free high-orders-pages in buddy instead of signal pages, it will decrease > COMPACT_STALL and speed up memory allocation. Okay, but then I assume the target goal of your patch set is to minimize CPU consumption/allocation stall time when allocating larger order pages. Currently you state "the probablity of high-order-pages allocation would be increased significantly", but I assume that's then not 100% correct. What you measure is the stall time to allocate higher order pages, not that you can allocate them. > > 2. record the speed of the high-orders-pages allocation(order=4 and > order = 8) > Before and after optimization, we tested the speed of the > high-orders-pages allocation > after 120-hours-Monkey in 10 Android mobile phones. and the result show that > the speed has been increased by more than 18%. > > Also, we do some test designed by us: > (the machine with 4 gigabytes of physical memery and in linux-4.19.) > model the usage of users, and constantly start and > operate the diffrent application for 120h, and we record COMPACT_STALL > is decreased by > 90+% and speed of the high-orders-pages is increaed by 15+%. Okay, again, this is then some optimization for allocation speed; which makes it less attractive IMHO (at least for more invasive changes), because I suspect this mostly helps in corner cases (Monkey benchmarks corner cases AFAIU). > > and I have some question, i hope you can guide me if when you are free. > 1) What is the compaction configured? >     Dost it meant the members in zone? like as follows: >     unsigned int compact_considered; >     unsigned int compact_defer_shift; >     int compact_order_failed; >     bool compact_blockskip_failed; >     Or the some Macro variable? like as follows: >     PAGE_ALLOC_COSTLY_ORDER = 3 >     MIN_COMPACT_PRIORITY = 1 >     MAX_COMPACT_RETRIES = 16 > Rather if you have proactive compaction (/proc/sys/vm/compaction_proactiveness). But I assume because you're messing with older kernels, that you didn't compare against that yet. Would be worth a comparison. >>> 1) multi freearea (which might > >> be problematic with sparcity) > 2) Can you pls tell me what is soarcity and what is the impact of this? >     and whether there are some documents about it? Essentially CONFIG_SPARSEMEM, whereby we can have huge holes in physical memory layout and memory areas coming/going with memory hot(un)plug. Usually we manage all metadata per section. For example, pageblocks are allocated per section. We avoid arrays that depend on the initial/maximum physical memory size. -- Thanks, David / dhildenb