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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93be0e54ff3sm144885585a.9.2026.09.18.06.57.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2026 06:57:06 -0700 (PDT) Date: Fri, 18 Sep 2026 09:57:04 -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 3/4] sched/numa: scan read-only file mappings in tiering mode Message-ID: References: <20260911001826.2109390-1-gourry@gourry.net> <20260911001826.2109390-4-gourry@gourry.net> <0ed3ab3a-80b4-492f-867a-0584441722a9@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0ed3ab3a-80b4-492f-867a-0584441722a9@kernel.org> On Fri, Sep 18, 2026 at 02:58:36PM +0200, David Hildenbrand (Arm) wrote: > > +/* > > + * Read-only file-backed mappings are expected to be cache replicated between > > + * accessor nodes, so they are not worth sampling for placement. They can > > + * still strand on the slow tier like anything else. > > + */ > > +static bool vma_is_ro_file(struct vm_area_struct *vma) > > +{ > > + return vma->vm_file && (vma->vm_flags & (VM_READ | VM_WRITE)) == VM_READ; > > > MAP_PRIVATE can easily map a read-only file with write permissions. So the > function name is a bit misleading. > > This smells like a helper that should go next to other vma helpers and have > clear semantics. > No argument here. Would like to balance improvement vs backportable bugfix though. I broke out the name to try to make it at least a bit more readable. > > if (!vma->vm_mm || > > - (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) { > > + (vma_is_ro_file(vma) && > > + !(numab_mode & NUMA_BALANCING_MEMORY_TIERING))) { > > I'd vote for >80c here and but it into a singe line. > > Or just use a magical helper > > const bool tiering = numab_mode & NUMA_BALANCING_MEMORY_TIERING; > > or sth like that. > ack > > trace_sched_skip_vma_numa(mm, vma, NUMAB_SKIP_SHARED_RO); > > continue; > > } > > @@ -4306,7 +4316,8 @@ static void task_numa_work(struct callback_head *work) > > continue; > > } > > > > - promo_only = !(numab_mode & NUMA_BALANCING_NORMAL); > > + promo_only = !(numab_mode & NUMA_BALANCING_NORMAL) || > > + vma_is_ro_file(vma); > > As I said, maybe that flag could be voided. > ack.