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Tue, 21 Jun 2022 08:28:05 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 46128AE045; Tue, 21 Jun 2022 08:28:00 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2453FAE053; Tue, 21 Jun 2022 08:27:54 +0000 (GMT) Received: from [9.43.38.129] (unknown [9.43.38.129]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 21 Jun 2022 08:27:53 +0000 (GMT) Message-ID: Date: Tue, 21 Jun 2022 13:57:52 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v5 1/9] mm/demotion: Add support for explicit memory tiers Content-Language: en-US To: Jonathan Cameron , Johannes Weiner , Tim C Chen Cc: linux-mm@kvack.org, akpm@linux-foundation.org, Wei Xu , Huang Ying , Greg Thelen , Yang Shi , Davidlohr Bueso , Brice Goglin , Michal Hocko , Linux Kernel Mailing List , Hesham Almatary , Dave Hansen , Alistair Popple , Dan Williams , Feng Tang , Jagdish Gediya , Baolin Wang , David Rientjes References: <20220603134237.131362-2-aneesh.kumar@linux.ibm.com> <02ee2c97-3bca-8eb6-97d8-1f8743619453@linux.ibm.com> <20220609152243.00000332@Huawei.com> <20220610105708.0000679b@Huawei.com> <20220614174539.00004145@Huawei.com> From: Aneesh Kumar K V In-Reply-To: <20220614174539.00004145@Huawei.com> Content-Type: text/plain; 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bh=cqcomHDjPnfOqjVnU/f6TqQB1rpo3bhz5KUCGCRMf44=; b=R8H9yQEiNUDEEa4QCg5rY85MTerDYM1GRaIIKqoEKHkmq+flxlC2KlSijva37F5viFQunc QwUtRT4BP2QWj55+ZRGYf9mm72plHAHTHod9QqaTwG/FC5pTpaWFY9VQxEoLAt4Jdaqdaj KCLcWTCJ3df656OhHEs4/no0Ixcm9Q0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1655800104; a=rsa-sha256; cv=none; b=BxzD9Vbw05+PTbe5P0YRaCrUn0oA0qQWLXb6cX2VB7LLyBfmB6yLaFzt3O8Sb67miNAYtA aV+HL5sRM6UTCDXovR8d9dcyn97xoS7yisymxI2avRTHkhxGbZf8LZb0fRoJAC5x5scuPH ADp+R3PVrPlakWtvheSsFORa5Vo3VCo= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=q0tGtJJY; dmarc=pass (policy=none) header.from=ibm.com; spf=pass (imf27.hostedemail.com: domain of aneesh.kumar@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=aneesh.kumar@linux.ibm.com Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=q0tGtJJY; dmarc=pass (policy=none) header.from=ibm.com; spf=pass (imf27.hostedemail.com: domain of aneesh.kumar@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=aneesh.kumar@linux.ibm.com X-Rspamd-Server: rspam12 X-Rspam-User: X-Stat-Signature: puomubjak54hn7nmupp7kkwsuf9eryfu X-Rspamd-Queue-Id: 6CA624001C X-HE-Tag: 1655800104-32147 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 6/14/22 10:15 PM, Jonathan Cameron wrote: > ... >> >> It could be simple tier0, tier1, tier2 numbering again, but the >> numbers now would mean something to the user. A rank tunable is no >> longer necessary. > > This feels like it might make tier assignments a bit less stable > and hence run into question of how to hook up accounting. Not my > area of expertise though, but it was put forward as one of the reasons > we didn't want hotplug to potentially end up shuffling other tiers > around. The desire was for a 'stable' entity. Can avoid that with > 'space' between them but then we sort of still have rank, just in a > form that makes updating it messy (need to create a new tier to do > it). > >> How about we do what is proposed here https://lore.kernel.org/linux-mm/7b72ccf4-f4ae-cb4e-f411-74d055482026@linux.ibm.com The cgroup accounting patch posted here https://lore.kernel.org/linux-mm/cover.1655242024.git.tim.c.chen@linux.intel.com looks at top tier accounting per cgroup and I am not sure what tier ID stability is expected for top tier accounting. -aneesh