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Thu, 26 Mar 2026 07:01:40 +0000 (GMT) From: Donet Tom To: David Hildenbrand , Andrew Morton , Ingo Molnar , Peter Zijlstra Cc: Ritesh Harjani , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Baolin Wang , Ying Huang , Juri Lelli , Mel Gorman , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Donet Tom Subject: [PATCH] sched/numa, mm: Skip page promotion if cpu pid is valid Date: Thu, 26 Mar 2026 02:12:16 -0500 Message-ID: <20260326071216.11883-1-donettom@linux.ibm.com> X-Mailer: git-send-email 2.47.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: CiaSF-H1fnPPyV5xXc-MOYz_Qk5Hvnp8 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI2MDA0OSBTYWx0ZWRfX4KLfaAC6v9T5 PRpSrbBqH09ZlYLbFNG3BZ6ZBuoLbcHwrQrVnCIrVtpPdFjb0blSvwXRjcT6NtxbHSqGvZsQA5Y zhNPEUdV2i1fkRfSyr7QMiNMlenU3qjN92lBESP9Q6GfMuMA4Jt+iMvrcvK2mNR6pP3TfbLetbG U4pVtmFM+zAoLf/zLIxVmBXj0L+PLa17xYnSGWZvJzzvXMKuAagOIGeX/AVRyqHDQMyEAYWm8Bz M6C41n6axuXvqCGuOR5Ux9kitHlWmFBqQzhUMH1eLAjnMZpfhbaWqkV1Yz0XO38uDunhDjdCjnu Dt7d16reyiOaFFNoGMUewV1F50jYOtm6HJ/2zRgY6wdpV5zzMdQxlqTEnWr8he4keo8a7QXxsak r9hJTEWew0hOVVOdwrXweTNmRBGfF6QN1eeyUWnbVPdSZFShm+xQmeciL8KXbYB12/l4tNbYemC EF8L2fPYf9j26oWAx7A== X-Authority-Analysis: v=2.4 cv=bLEb4f+Z c=1 sm=1 tr=0 ts=69c4d9db cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=BU45FUZf6EOTpP1Kgp0A:9 X-Proofpoint-GUID: MJCi38OmNnXbfplKA4HoCHDbAQwVLJJo X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-26_02,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 adultscore=0 clxscore=1011 phishscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 suspectscore=0 bulkscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603260049 Content-Type: text/plain; charset="utf-8" If memory tiering is disabled, cpupid of slow memory pages may contain a valid CPU and PID. If tiering is enabled at runtime, there is a chance that in should_numa_migrate_memory(), this valid CPU/PID is treated as a last access timestamp, leading to unnecessary promotion. Prevent this by skipping promotion when cpupid is valid. Signed-off-by: Donet Tom Acked-by: David Hildenbrand (Arm) --- kernel/sched/fair.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 4b43809a3fb1..f5830a5a94d5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2001,6 +2001,13 @@ bool should_numa_migrate_memory(struct task_struct *= p, struct folio *folio, unsigned int latency, th, def_th; long nr =3D folio_nr_pages(folio); =20 + /* When tiering is enabled at runtime, last_cpupid may + * hold a valid cpupid instead of an access timestamp. + * If so, skip page promotion. + */ + if (cpupid_valid(folio_last_cpupid(folio))) + return false; + pgdat =3D NODE_DATA(dst_nid); if (pgdat_free_space_enough(pgdat)) { /* workload changed, reset hot threshold */ --=20 2.47.1