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imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=LoZbd6DX; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789735085; b=ywi8dzCH26qNkxvDXFnelvLJZM0ZKxcMdGQ1YpGEA+u+h2a72KzqOSkyPAh6QK2cuDhZ1v 8ep56hMssnpcidoHfJ63x0BqAI9crv5RFG8fL9ghTS6uVZ4fiILnNghfSfYaLeaMuRBNft pfrXUIwPyiD8b5hWFMrZefeAalVrsHw= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id CD0054021C; Fri, 18 Sep 2026 12:38:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 947D61F000FF; Fri, 18 Sep 2026 12:37:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789735084; bh=HjoRpOQGdgI3jF+/9FxZtTBNtq2uuhw/a+czWqehIM8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=LoZbd6DX+pORy/h4fvGM0bK/UMuJASInrc3aY0qebM0smo4PSbMjAIYGHbyb9qfNl mJX810DP29QPXgcnaxoZ2coqKfT6thKV1upOUwNADFZz8JbYSELHAf6M5MjE8p5/6D 5jCBJgIh5/cqulc9plkjr4sRe/H18SqW+mZJER5mGBzjNKE9cpaRrE/yw/a98Mvrmy WOOnxoZSv4mAeeMuo2/t2UdmkDPpVrSHk+VF1SKpqs4D36/r7IIpxazWxBbWPOzot/ 85FM4WCrhrmSIkEhEYtVQkqDJUWI8GGkcrt3rkKKX51ovy6U6HgTc6ZaDneAkbOZuX D2aAzvpwMWXOQ== Message-ID: <9b5e1573-6fd8-48a5-a274-a6e7ff83d2fe@kernel.org> Date: Fri, 18 Sep 2026 14:37:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] mm: support promotion-only NUMA hinting scans 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, 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 References: <20260911001826.2109390-1-gourry@gourry.net> <20260911001826.2109390-2-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-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: A934F18000B X-Stat-Signature: z6m9ddrky65wmxm349bnfgzcpudanq6r X-Rspam-User: X-HE-Tag: 1789735085-958622 X-HE-Meta: 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 JD10ABqv 4HKUuKKyhAxZEXqafk5i+tVyJ6Pe7RmZFUg8azUzLUsR74o0y1XDF2/6wPK8l81hULUJEoP92cd9eOjFeU2Hke+QE0G7mo/wyPhIHUdVI8/XI4nDiYbZBAtqqw5tt53pf5yN3VLpcCVMcSdAMCpI9PKd/qMUj7F2rLQOG7Ab34R2BIVn9c83PKiSy4X1zzKwWJIKUEPw9VvImjBB4lTJ1PF/LA+2TzRsr+FRlKR8F9XCKPdzt+dC7R8xqzCMNnUooH2vQHZg/VzbotUEDbRCKYcBRiScmobhDbcw/M0WSUnRchGi/IjjY7egnXnCDn2+sNpSvgidAzENk3Qbri+WR8etuwlzlmVcXKbt6SFjEEeWg8Gkhlk1Y2ZzRJhxrJM5Ch655ka6S9Q1VKzEVJqBt3GkID/Dp/05D7l0L8Cnj/IxVfp8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/11/26 02:18, Gregory Price wrote: > From: "Gregory Price (Meta)" > > folio_can_map_prot_numa() derives the eligible memory from the global > balancing mode. Combined mode needs the scanner to distinguish placement > scans from promotion-only scans. > > Add MM_CP_PROT_NUMA_PROMO_ONLY and let change_prot_numa() callers request > a promotion-only protection walk. Carry the choice with each walk so the > PTE and PMD paths use the same decision. > > Initially derive the value from the normal balancing mode, preserving the > existing behavior for the following fixes. > > Fixes: c574bbe91703 ("NUMA balancing: optimize page placement for memory tiering system") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Gregory Price (Meta) > --- > include/linux/mm.h | 4 +++- > kernel/sched/fair.c | 7 ++++++- > mm/huge_memory.c | 3 ++- > mm/internal.h | 5 +++-- > mm/mempolicy.c | 22 +++++++++++++--------- > mm/mprotect.c | 4 +++- > 6 files changed, 30 insertions(+), 15 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 969594074fd2..2d1b59a27629 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3408,6 +3408,8 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); > #define MM_CP_UFFD_RWP_RESOLVE (1UL << 5) /* resolve rwp */ > #define MM_CP_UFFD_RWP_ALL (MM_CP_UFFD_RWP | \ > MM_CP_UFFD_RWP_RESOLVE) > +/* Whether a MM_CP_PROT_NUMA change is for promotion only */ > +#define MM_CP_PROT_NUMA_PROMO_ONLY (1UL << 6) BTW, shouldn't we just be using BIT()? > > bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > pte_t pte); > @@ -4736,7 +4738,7 @@ void vma_set_file(struct vm_area_struct *vma, struct file *file); > > #ifdef CONFIG_NUMA_BALANCING > unsigned long change_prot_numa(struct vm_area_struct *vma, > - unsigned long start, unsigned long end); > + unsigned long start, unsigned long end, bool promo_only); While at it use two tabs. > #endif > > struct vm_area_struct *find_extend_vma_locked(struct mm_struct *, > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 8dff37059faf..81359b414947 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4129,8 +4129,10 @@ static void task_numa_work(struct callback_head *work) > unsigned long nr_pte_updates = 0; > long pages, virtpages; > struct vma_iterator vmi; > + unsigned int numab_mode = READ_ONCE(sysctl_numa_balancing_mode); const and all the way to the top? > bool vma_pids_skipped; > bool vma_pids_forced = false; > + bool promo_only; > > WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work)); > > @@ -4304,11 +4306,14 @@ static void task_numa_work(struct callback_head *work) > continue; > } > > + promo_only = !(numab_mode & NUMA_BALANCING_NORMAL); bool promo_only = !(numab_mode & NUMA_BALANCING_NORMAL); and in the later patch if (vma_is_ro_file(vma)) promo_only = true; ? But ... > + > do { > start = max(start, vma->vm_start); > end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); > end = min(end, vma->vm_end); > - nr_pte_updates = change_prot_numa(vma, start, end); > + nr_pte_updates = change_prot_numa(vma, start, end, > + promo_only); Stupid question: why can't/shouldn't change_prot_numa() query sysctl_numa_balancing_mode? Why do we have to query this outside of the function and forward it? I mean, change_prot_numa() gets the vma and can query sysctl_numa_balancing_mode. Why not move that into the function and avoid the boolean parameter? We do have a single change_prot_numa() caller in the tree ... > > /* > * Try to scan sysctl_numa_balancing_size worth of > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 30b7c63b0e35..2f9ada1bbcfc 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2784,7 +2784,8 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > goto unlock; > > if (!folio_can_map_prot_numa(pmd_folio(*pmd), vma, > - vma_is_single_threaded_private(vma))) > + vma_is_single_threaded_private(vma), > + cp_flags & MM_CP_PROT_NUMA_PROMO_ONLY)) As raised, maybe just forward cp_flags -- Cheers, David