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b=AXyYcsq9/FFTDLVDfuaLhYscCqLUFDph4zsoXj5QTlmOADNMX51iD0SkOytpuf5MO On7NZDhoFLjM6CWVW2gzFEcvlQfJlOxXWG7tWYqM47OAMu7KAyTJd7YFvQOmfAC17f pUVold2MOFnaPPOqct7QNwYVg+o854Z573vOoPA2MqB1mA056rQO7/yQCAetpOVFcR DU96bxWqJMrGQzyE+IpFrPq0TBmt2WYo1ugFcGZcDcEtbALPfyGcbim8nxi0gLfM37 GlcYsri4WfmEBwTtjSQrTwwgvb8pzlnlZMraSyWbadX19Qf1ifbAwyTUxBkutck3ZK jzOuD2flcr5bw== Message-ID: Date: Thu, 1 Oct 2026 12:44:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/7] sched/numa: separate VMA placement from scan continuation To: Gregory Price , linux-mm@kvack.org Cc: 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, 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, shy828301@gmail.com, osalvador@suse.de, raghavendra.kt@amd.com, stable@vger.kernel.org References: <20260930112206.205083-1-gourry@gourry.net> <20260930112206.205083-5-gourry@gourry.net> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: a85bgycf3xit5ccbeyi3wh5ujpfdtaij X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 00BD94000B X-HE-Tag: 1790851505-509227 X-HE-Meta: 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 LLWWokEU jM5WtZzDpEFYImVOAkzFU/uD8k8QyRnqNtJDOTBuakw5EfLVEg8dUrBc6xi6g9kIsp6NJ7lP6SccnxzUTC8gyGIv+hIADQLM74j8te4VnZJKzWqAK6QbBCMfTf8wCtziBDAGh97rjXivf7oaYDjrODydFuMm6IuFjjDks148FKpB70oPpxJ/2kGAdPGJdkNViC1sAj1YEPDO4OhAYSHqQ/SzoCEoPs1Tg3x3pU1k20ur0IcFsVBVVUWtSBONhf6Pax1YCjYn60Io2YYoDprFnH20gqkZqQzYPOHxTHxIF3QSzomN9XcngiClfY2Rrspw5L+tVhN6OprhNGKTaFMMifCudC2QWKMgSTk8ci0U9RkM7GfTStSYkfOvB+iN6iBd0ZtDyiJUV3itxEzZ7GLVv6+iPqLfyUqrq2T+I Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/30/26 13:22, Gregory Price wrote: > From: "Gregory Price (Meta)" > > vma_is_accessed() returns true both when a VMA needs placement > (east-west) sampling and when a VMA is already mid-scan across > multiple scan windows. > > Callers cannot distinguish placement eligibility from scan progress. > > Rename the helper to vma_needs_placement_scan() and handle continuation > state in task_numa_work(). Record whether an in-progress VMA scan is > promotion-only so a scan resumed in a later scan window finishes with > the policy it started with. The zeroed initial state places no > restriction, so a resumed scan that finds freshly allocated NUMAB state > falls back to the default policy. > > This separation allows PID-inactive VMAs to be scanned for promotion > without treating scan continuation as evidence of placement eligibility. > It is a prerequisite for the following fix and must accompany it when > backported. > > Fixes: fc137c0ddab2 ("sched/numa: enhance vma scanning logic") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Gregory Price (Meta) > --- > include/linux/mm_types.h | 6 ++++++ > kernel/sched/fair.c | 40 ++++++++++++++++++++++++---------------- > 2 files changed, 30 insertions(+), 16 deletions(-) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 1bd3ca7bfff2..d0ac21d02c47 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -803,6 +803,12 @@ struct vma_numab_state { > * A VMA is not eligible for scanning if prev_scan_seq == numa_scan_seq > */ > int prev_scan_seq; > + > + /* > + * The in-progress scan of this VMA is promotion-only. > + * Resumed scans finish with the policy they started with. > + */ > + bool promo_only; > }; > > #ifdef __HAVE_PFNMAP_TRACKING > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ab9afd3ad49b..3b30786ded3b 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4082,7 +4082,8 @@ static void reset_ptenuma_scan(struct task_struct *p) > p->mm->numa_scan_offset = 0; > } > > -static bool vma_is_accessed(struct mm_struct *mm, struct vm_area_struct *vma) > +static bool vma_needs_placement_scan(struct mm_struct *mm, > + struct vm_area_struct *vma) mm can be had from vma->vm_mm, so likely sufficient to only pass the vma? Apart from that this looks much clearer to me Acked-by: David Hildenbrand (Arm) -- Cheers, David