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charset="UTF-8" ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=RzaFy7ux; spf=pass (imf22.hostedemail.com: domain of huang.ying.caritas@gmail.com designates 209.85.215.176 as permitted sender) smtp.mailfrom=huang.ying.caritas@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660634902; a=rsa-sha256; cv=none; b=DU5MQmV5CZEpq1yhvWZkH18CeLCAbU7VsV6kRNnKQYhVmumtyM0cU1MpERDmtKv4Pb0NE+ fwWrusPh1NkX8vu1zXVZlrrWc2yW/xoRhhpuAWOGLdCK72pLV21/FHvN0+oMckFX7/DZRy 6MyVK2h4mcc9a1PhRz4hTfK+Sc8hk4o= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660634902; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=QSsvuBZDO6bQt7jMT8PKkHwExip9fgIO0FXnSkmtOLk=; b=0nG1Ur8n4HV+zQ9q8M9DW1f3MczSVTq2+UGWxbdXhDEZ+l8G/exILYPI23Mew1xHc39YFP OCH7ncXcozsg5uTrAYgKm8W6/y5G0FM36uVqXfFtFJx3vt4szeNtgV4KAcY1X5oZ7U3udr A5YvsJ4OKajXx6FAee2szL4P/eJd37s= Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=RzaFy7ux; spf=pass (imf22.hostedemail.com: domain of huang.ying.caritas@gmail.com designates 209.85.215.176 as permitted sender) smtp.mailfrom=huang.ying.caritas@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: bq9z5kwqckodtxf9g8rix31ixzu4kgxw X-Rspamd-Queue-Id: B7828C018A X-HE-Tag: 1660634902-465727 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 Tue, Aug 16, 2022 at 1:10 PM Aneesh Kumar K V wrote: > > On 8/15/22 8:09 AM, Huang, Ying wrote: > > "Aneesh Kumar K.V" writes: > > [snip] > >> > >> +/* > >> + * Default abstract distance assigned to the NUMA node onlined > >> + * by DAX/kmem if the low level platform driver didn't initialize > >> + * one for this NUMA node. > >> + */ > >> +#define MEMTIER_DEFAULT_DAX_ADISTANCE (MEMTIER_ADISTANCE_DRAM * 2) > > > > If my understanding were correct, this is targeting Optane DCPMM for > > now. The measured results in the following paper is, > > > > https://arxiv.org/pdf/2002.06018.pdf > > > > Section: 2.1 Read/Write Latencies > > > > " > > For read access, the latency of DCPMM was 400.1% higher than that of > > DRAM. For write access, it was 407.1% higher. > > " > > > > Section: 2.2 Read/Write Bandwidths > > > > " > > For read access, the throughput of DCPMM was 37.1% of DRAM. For write > > access, it was 7.8% > > " > > > > According to the above data, I think the MEMTIER_DEFAULT_DAX_ADISTANCE > > can be "5 * MEMTIER_ADISTANCE_DRAM". > > > > If we look at mapping every 100% increase in latency as a memory tier, we essentially > will have 4 memory tier here. Each memory tier is covering a range of abstract distance 128. > which makes a total adistance increase from MEMTIER_ADISTANCE_DRAM by 512. This puts > DEFAULT_DAX_DISTANCE at 1024 or MEMTIER_ADISTANCE_DRAM * 2 If my understanding were correct, you are suggesting to use a kind of logarithmic mapping from latency to abstract distance? That is, abstract_distance = log2(latency) While I am suggesting to use a kind of linear mapping from latency to abstract distance. That is, abstract_distance = C * latency I think that linear mapping is easy to understand. Are there some good reasons to use logarithmic mapping? Best Regards, Huang, Ying