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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0ed3ab3a-80b4-492f-867a-0584441722a9@kernel.org> X-Rspam-User: X-Stat-Signature: ze88tjf436ka15gawbaeeuquxuh5gjmd X-Rspamd-Queue-Id: 3E9DB140007 X-Rspamd-Server: rspam07 X-HE-Tag: 1789739828-180186 X-HE-Meta: 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 HccYF47o oo38AwkIMDCfWiYNoNFZ5KCQO7LK0xYNNpa6RVa3fYTwSGynxUeEz8qbfjbV1nF7B+IHzblS0wOcQWvEIFpTzGEHNncZfZjzF2Re6Y907p8eOEGzKwFhKDT4yDCZ7VE4QIJ1lq4d0d5gvIQBn47fjQHZjkWIuLtCbaKag3SDzmsitfJtvAHet1hKYdjvTm+B/PlCuS75YX5mqUC7+UdbZxl8L+IzLdSkzjVAGuoNIBn+ITO+s1RyZN0ooDJWqba6XhteMaR7O6JQp5RUlBIcJZ/eu4z/HNApAACIf/2AWsCx3clVkKeJ2SxiqmG5hHZhnlANgFFGtZRYmhVHYGBcmWUiQml/yoO6rgtSMjL+9jg2bzGLTeWOWmR4edgBbVYZ60qARGpRWZVrmqQzyqZrHo22ZcQ== 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 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.