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[71.191.145.202]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-91f23db49c5sm28150796d6.41.2026.11.13.12.44.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 12:44:11 -0800 (PST) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [PATCH v5 5/7] sched/numa: scan PID-inactive VMAs for promotion From: "Gregory Price (Meta)" To: "Gregory Price (Meta)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@techsingularity.net, mingo@kernel.org, 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, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, matthew.brost@intel.com, byungchul@sk.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, hannes@cmpxchg.org, osalvador@suse.de, raghavendra.kt@amd.com, stable@vger.kernel.org In-Reply-To: <179434297609.2530531.2349001562856798404.b4-reply@b4> References: <20261110150446.2452975-1-gourry@gourry.net> <20261110150446.2452975-6-gourry@gourry.net> <179434297609.2530531.2349001562856798404.b4-reply@b4> Date: Fri, 13 Nov 2026 15:44:10 -0500 Message-Id: <179460265050.482102.15374067770225444971.b4-reply@b4> X-Mailer: b4 0.17-dev On 2026-11-10 15:36 -0500, Gregory Price (Meta) wrote: > On 2026-11-10 10:04 -0500, Gregory Price (Meta) wrote: > ... snip ... > > Sashiko report feedback > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -4249,7 +4249,7 @@ static bool vma_needs_placement_scan(struct vm_area_struct *vma) > > * threads can help scan this vma, force a vma scan. > > */ > > if (READ_ONCE(mm->numa_scan_seq) > > > - (vma->numab_state->prev_scan_seq + get_nr_threads(current))) > > + (vma->numab_state->prev_placement_scan_seq + get_nr_threads(current))) > > return true; > ... snip ... > > + if (placement_scan) > > + vma->numab_state->prev_placement_scan_seq = mm->numa_scan_seq; > > Sashiko took issue with these skips, but its reported impact is > overstated. It tries to point out a pre-existing condition: > > prev_scan_seq skips an update on a rare corner condition, but > now the same skip applies to prev_placement_scan_seq. > > In modes 1 (placement) and 2 (tiering), the behavior is exactly the > same as it was. > > In mode 3 (placement + tiering) the result is that the starvation > counter isn't reset - but everything still works anyway because the > VMA is still being scanned. > > I can follow up with *another* commit, but it's really low impact. > Not sure it's worth the churn. > I will refresh this next week and just address it in another commit. -- ~Gregory