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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=v6oWupOTxMkZT/KhS528vX3zYkNGL3N/FEeWSRmmOn0=; b=IXSGcT5CNATvX7JkhhRsxxTOwhHwV1ET/zaKmGwMXXL8M6cez2xVXzdvwp92FuOxP4 b5eGUhqqeqg9RMGaeuCZjLYFQchp9h0u+1+VCP3cDetNS2TkzS50RDnhAYbuG8U6fS8B 5StFy3pDkvFnD+5PUXq4MO31DkVrlyaZyoVJGgQHZ5w0KGPPxKjx9JBKDBOmv1wqEWe6 0ZgibK0RgQCGD++ErAv+s1Bc9Aa2TGdClcaBk4juZsfrVnz79AeQ3U73kVL3Nvt+lXKa f5yatJaUL+TCQ2Q7ZFNtx0aG3N29m8Ttg+bSRxw0iUoMT7Eyq6KeMF7DmOGyASUUJMEV 0rFg== X-Gm-Message-State: AOAM533EH/504TDCnE45P/hbHDLrsX+rXTWyqCryunZXJ2MIdC419eHe VafIFvGtOaxVl8WW02nbRvx5mBShKN92o0CjHW0= X-Google-Smtp-Source: ABdhPJxH0XzNQzl9TcQjuTfwZ7PhmoiQBIe37e4xF+yjRvEbkbD9HcxSYFa/hyG/k8wZRs8/H8Fk8X+j5HWnfA2rOuk= X-Received: by 2002:a05:6830:20d6:: with SMTP id z22mr18863076otq.94.1597842771741; Wed, 19 Aug 2020 06:12:51 -0700 (PDT) MIME-Version: 1.0 References: <1596435031-41837-1-git-send-email-pullip.cho@samsung.com> <5f41af0f-4593-3441-12f4-5b0f7e6999ac@redhat.com> <20200818085444.GA72202@KEI> In-Reply-To: <20200818085444.GA72202@KEI> From: Pekka Enberg Date: Wed, 19 Aug 2020 16:12:32 +0300 Message-ID: Subject: Re: [PATCH] mm: sort freelist by rank number To: Cho KyongHo Cc: David Hildenbrand , Andrew Morton , "linux-mm@kvack.org" , LKML , hyesoo.yu@samsung.com, janghyuck.kim@samsung.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: F1615180CE69E X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: Hi KyongHo and David, On 07.08.20 09:08, Pekka Enberg wrote: > > > I think having more knowledge of DRAM controller details in the OS > > > would be potentially beneficial for better page allocation policy, so > > > maybe try come up with something more generic, even if the fallback to > > > providing this information is a kernel command line option. On Tue, Aug 18, 2020 at 12:02 PM Cho KyongHo wrote: > I don't find if there is a way to deliver detailed DRAM information > through ACPI, ATAG or something similar. But I didn't find. Perhaps that's still the case today then. In the context of this patch, what I am hoping is that we'd turn the "dram_rank_granule" parameter -- even if it's still a manually configured thing -- into an abstraction that we can later extend. IOW, something similar to what the "energy model" (kernel/power/energy_model.c) today is. On Mon, Aug 10, 2020 at 09:32:18AM +0200, David Hildenbrand wrote: > I guess one universal approach is by measuring access times ... not what > we might be looking for :) I don't think it's an unreasonable approach, but measurement accuracy and speed will determine if it's actually practical. There are examples of this kind of approach elsewhere too. For example, MCTOP [1] which aims to provide topology-aware OS abstractions, uses cache latency measurements to infer the topology. 1. https://timharris.uk/papers/2017-eurosys-mctop.pdf Regards, - Pekka