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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93be0e508a2sm143621485a.11.2026.09.18.06.59.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 06:59:39 -0700 (PDT) Date: Fri, 18 Sep 2026 09:59:37 -0400 From: Gregory Price To: "David Hildenbrand (Arm)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, osalvador@suse.de, hannes@cmpxchg.org, raghavendra.kt@amd.com, stable@vger.kernel.org Subject: Re: [PATCH v2 4/4] sched/numa: do not let VMA PID activity gate promotion Message-ID: References: <20260911001826.2109390-1-gourry@gourry.net> <20260911001826.2109390-5-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2356B40002 X-Stat-Signature: bhnduyykqzj6fb3dhf737bfht6bidpaj X-HE-Tag: 1789739980-328718 X-HE-Meta: U2FsdGVkX1+98MPnluozka6sxW8V1cExv/LQNS1qkyVavEq2Q6XJCZLj6aodMEntPc4YRGp9tNkR4pP8+faOoj0k2WRjfAvHkz3sIGOLmxdy/Pc2V7z0f1KbjISZM2LZp4alTl87A86fTXVgx13Na1iI8biEHJni5fcfok7SqSrxfmBiXRcgEw9Tu7BpxdPIy2R4pwDeBtb32LYkxO+0HzUkvOa002+i8Zjj6gAfTInMljF5yrDuStTs2OZ4T37/hBuqFvdzTSrgK3nO/M21YrrgETVl9mrlGR1EWIpw2r5TgZTyB9a9cYyLPBvcSnALYIzqALzYRC1WGMF/DSsyjmrhTDO9aw2s78V1iL3fX8IIpimnd6t0smEwM2PZWRjM6c3PRIw/uJRahs0z/kAfFMlY46/dATLeQyXHxNSVpoLqndHQ6+ulP4Qak5HthZMV5djE5grNVgnP8NlTYzDyyYTA2XGwMMbwZsru4QhiygHb4sfRfY/8WkXUxV1tDlIRDO13qwQQbCTgC1UlY8R09ezV2UMCZ/sN44MQoGSRsm/Tk5JTY5b/MrAcT6Fb0vbsAIicKVhnxPmzZ46FWsbYUDNmwvcZuzPVd3VJe/Cet3fFJNdy5V8aLzNCd8G6abNePibeHq85CjVWJpEw+GOm+n7wwcbF9I4eAgjJrGslJ40bCosDMVKfblTcyN8jxGDdsc3Y8Ba9/f7XBdkIcvCrgn9YSMvGiwA8AltTWh/5pXiL50mBs5rnOwmN91TI3KgLZ1lygLhYl23DmdaV8aONsld3uY7sUh7iFH/m4dx2Th2W1wW5gbtL68i5cJc/HPgcfF0NU+Qlar4mb0Og14JpAoPtAor/N+FNqQGQ+gzJdZvXSMT1LltSg7dhrjFg90C5XBRABl8+U3tM3Fmj8fZO0FScuLvUXkcMGK/FJEHRmv0BxykL4Zm7aeNGKgNxFBvU2soGsia+v3vY4EvhC4E Gi7jrq3y HvdOViq6pvGtfIfuo75dI6hPHK/tDZ+Rjln9MitLK3rvIBiaYxekjavW9aLk/U/oJ+5C7hOoxe3UCUaj34IFljlA41tI3vhbiZ4ZEHXNh/nqyCy5/Gjb37+5XhxYzl+Nit1XhRRgkubi4/LkDKFkKtLGdYK8hr7BqAwMVjUQbI5JXUtRupn3BCe9B3RnbPQ6A4/w2NkK3FoL6ocwa3oHQIgzH4HQAECfUytJq24aGXVS0GAiISr4mUS1sjT+Ieq5QnB5e+KEAjTvDGjUZ1he1oA4l0Dy/dsDILUdbtLnMVX99WVnkbwfFvxpe/X6qvpsh2jchSifYmnPubxXIHjuKAiu2eX3yyCde+nvWp3llWhycmNSZHpTUY/l8bKDJyLj5UMIB2Ui7ORbGAp+0TCy2o8ZB7w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Sep 18, 2026 at 03:01:34PM +0200, David Hildenbrand (Arm) wrote: > > - /* VMA scan is complete, do not scan until next sequence. */ > > + /* > > + * VMA scan is complete, do not scan until next sequence. A > > + * promotion-only scan reached the end of the VMA but did not > > + * sample placement, so it does not count towards the starvation > > + * horizon in vma_is_accessed(). > > + */ > > vma->numab_state->prev_scan_seq = mm->numa_scan_seq; > > + if (!promo_only) > > + vma->numab_state->prev_placement_scan_seq = mm->numa_scan_seq; > > > This is all rather ... messy. I mean, just look at that promo_only() computation ... > > There must be a cleaner way ;) I tried 3 or 4 different ways, this is the least ugly thing I could come up with :\ The scan sequence thing is particularly confusing, and numab=3 mode (NORMAL|TIERING) makes trying to reason about this whole thing really painful. I can see about making it at least a bit easier on the eyes. ~Gregory