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Fri, 3 Oct 2025 10:41:43 +0100 Date: Fri, 3 Oct 2025 10:41:41 +0100 From: Jonathan Cameron To: Raghavendra K T CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [RFC PATCH V3 09/17] mm: Add initial scan delay Message-ID: <20251003104141.00001744@huawei.com> In-Reply-To: <20250814153307.1553061-10-raghavendra.kt@amd.com> References: <20250814153307.1553061-1-raghavendra.kt@amd.com> <20250814153307.1553061-10-raghavendra.kt@amd.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml100011.china.huawei.com (7.191.174.247) To dubpeml100005.china.huawei.com (7.214.146.113) X-Stat-Signature: spys6uc1oyuxct6zqeje3zb7xbcrrb4e X-Rspam-User: X-Rspamd-Queue-Id: 96EC0140007 X-Rspamd-Server: rspam10 X-HE-Tag: 1759484508-126477 X-HE-Meta: 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 nczOqkQ6 Da++GcHV6P2YqSGknxk6UwYwPskOo5fxsge8iML9MqpPQP5NI1FOqxW+upvWe+GiBgqKqJbt2WZUQazHdWYbszQmK4Ymiq5R6JxgJQFpZ3KmREScfs/C2lDuLZspfyeCntRfxLUkpGinyVuboISt2b7aM/e2mWxTTDi0ryf2tlLCQw36x0pnjJZnQHSS5HmmM/I4XAFijt9UP6XFmpT7gixAVWG0t5kRhJdTs7Cx1avMTrBNNJ2KX0GTJNRZEa0HNli1AHexFC+OpViBmVIhM9x+tbSidM7PbCEA/tTljCcFIThitImzYDzov+XeoGM7gwg7a/fHNZy9B8S7rYY2GxpxHBaCKjYl3MRcj X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 14 Aug 2025 15:32:59 +0000 Raghavendra K T wrote: > This is to prevent unnecessary scanning of short lived tasks > to reduce CPU burning. Add a tiny bit on why reusing the existing sysctl value. Also useful to add a comment here on current default of that so when considering this algorithm we know what it is. > > Signed-off-by: Raghavendra K T > --- > mm/kscand.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/kscand.c b/mm/kscand.c > index 39a7fcef7de8..880c3693866d 100644 > --- a/mm/kscand.c > +++ b/mm/kscand.c > @@ -28,6 +28,7 @@ > > static struct task_struct *kscand_thread __read_mostly; > static DEFINE_MUTEX(kscand_mutex); > +extern unsigned int sysctl_numa_balancing_scan_delay; Maybe we need to move the declaration from kernel/sched/sched.h I'd rather see that than a somewhat hidden away extern declaration. > > /* > * Total VMA size to cover during scan. > @@ -1010,6 +1011,7 @@ void __kscand_enter(struct mm_struct *mm) > { > struct kscand_mm_slot *kscand_slot; > struct mm_slot *slot; > + unsigned long now; > int wakeup; > > /* __kscand_exit() must not run from under us */ > @@ -1020,10 +1022,12 @@ void __kscand_enter(struct mm_struct *mm) > if (!kscand_slot) > return; > > + now = jiffies; > kscand_slot->address = 0; > kscand_slot->scan_period = kscand_mm_scan_period_ms; > kscand_slot->scan_size = kscand_scan_size; > - kscand_slot->next_scan = 0; > + kscand_slot->next_scan = now + > + 2 * msecs_to_jiffies(sysctl_numa_balancing_scan_delay); I think one tab beyond line above is enough for indent here. > kscand_slot->scan_delta = 0; > > slot = &kscand_slot->slot;