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From: Roman Gushchin To: Sukadev Bhattiprolu Cc: Chris Goldsworthy , Rik van Riel , Andrew Morton , Roman Gushchin , Vlastimil Babka , Joonsoo Kim , Minchan Kim , Georgi Djakov , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm,page_alloc,cma: configurable CMA utilization Message-ID: References: <20230131071052.GB19285@hu-sbhattip-lv.qualcomm.com> <20230131201001.GA8585@hu-sbhattip-lv.qualcomm.com> <20230201040628.GA3767@hu-cgoldswo-sd.qualcomm.com> <20230202201302.GB22373@hu-sbhattip-lv.qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230202201302.GB22373@hu-sbhattip-lv.qualcomm.com> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: e7xjcpoaz1ir9j1b6rienkf59wbh58gu X-Rspam-User: X-Rspamd-Queue-Id: 894F1180015 X-Rspamd-Server: rspam06 X-HE-Tag: 1675469104-584257 X-HE-Meta: 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 8bEUfEm2 x/5pPPnfXJ6Wz3FI8ykOQ8DmXsf6goFS2orPGBpBLgMJeLOLgCPHUeSiFgOIqsXwIO+KFnoeAyrADRH9aFT8OJw8cziiOPZf3QsjIShc5+lbtVws9hgq4iQmca+jn+NLqeS9YD3umYY7Dx8RsGRxT6Qvzqr0y9iltQhE+SDpF0GWRJ+fiM9SMesmCSw== 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 Thu, Feb 02, 2023 at 12:13:02PM -0800, Sukadev Bhattiprolu wrote: > > Hi Roman, > > On Wed, Feb 01, 2023 at 11:00:25AM -0800, Roman Gushchin wrote: > > Then _maybe_ a new knob is justified, at least I don't have better ideas. > > Rik, do you have any input here? > > > > Let's then define it in a more generic way and _maybe_ move to the cma > > sysfs/debugfs (not 100% sure about this part, but probably worth exploring). > > We should be able to use a sysfs parameter too. Will try that out. Thanks. The reason I think it might be preferable is that new sysctls are hated by everyone and this use case looks a very niche. > But could you elaborate on what is more generic way? I mean in the proposed patch it's only possible to shift the ratio towards cma: a larger sysctl value will make allocations from the cma area happening earlier. The value 1 will turn it off completely. Probably better to define the new knob in % or 1/1000's with the default value 50% or 500. 0 will mean never use cma from this path, 999 - always. Something along these lines. Thanks!