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See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Queue-Id: 997E58000B X-Rspamd-Server: rspam05 X-Stat-Signature: gqnuy7acxer6qdu5x8c7r311hcawsco8 X-HE-Tag: 1741794768-284361 X-HE-Meta: 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 dP8kpA+n 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 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: List-Subscribe: List-Unsubscribe: On Wed, Mar 12, 2025 at 08:38:07AM -0700, Suren Baghdasaryan wrote: > I might be wrong but my understanding is that we should try to > allocate from CMA when the allocation is movable (not pinned), so that > CMA can move those pages if necessary. I understand that in some cases > a movable allocation can be pinned and we don't know beforehand > whether it will be pinned or not. But in this case we know it will > happen and could avoid this situation. Any file or anonymous folio can be temporarily pinned for I/O and only moved once that completes. Direct I/O is one use case for that but there are plenty others. I'm not sure how you define "beforehand", but the pinning is visible in the _pincount field. > Yeah, low latency usecases for CMA are problematic and I think the > only current alternative (apart from solutions involving HW change) is > to use a memory carveouts. Device vendors hate that since carved-out > memory ends up poorly utilized. I'm working on a GCMA proposal which > hopefully can address that. I'd still like to understand what the use case is. Who does CMA allocation at a time where heavy direct I/O is in progress?