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Wysocki" , Greg Kroah-Hartman , Danilo Krummrich , Zenghui Yu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, stable@kernel.org Subject: [PATCH v2 5/6] sched/cache: Skip kernel thread for cache aware scheduling Date: Mon, 21 Sep 2026 17:37:26 -0700 Message-Id: <058f0c6ea7b991c177a17de347fa3157f25489a7.1790035273.git.tim.c.chen@linux.intel.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D1035A0005 X-Stat-Signature: oproiz5hhjk5zyirpqnh61st5zd1hqyb X-HE-Tag: 1790037138-797795 X-HE-Meta: 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 5z0gYd9l BpSJghqSypgnZ1UI5WfAYnDP82vNYY67dY3StkbSg+14s4Jr/tP3VK3yLy/vtRXPDrQslZ4Go3sJpMMu2sL5b8VS8n8Lb9huEEoJP8zorIqlD47jE6gYKTb3MH33WkOx4DSa0EHK7yO2/kVSVgUjxTWf2yc7LCt4sfzo9ltFRmX/A0iKLls4edZU2/8MhIepEyyRQXO89zM9VbN4qALtvPWFMCfaVP7PGcMfnVZrP1OHCToToFoxRcIL3MeidF2XZSJAQDACB+tczbcz8WBKNnufYEQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Chen Yu Kernel thread should not be covered by cache aware scheduling as it borrows the statistics from the user space thread. Filter the kernel thread in account_mm_sched(). In theory a kernel thread does not have any valid cache group, so !grp should gate the kernel thread. Add the PF_KTHREAD check explicitly here for safety reasons, to guard against future modifications and to pair with task_tick_cache(). Fixes: df0d98475954 ("sched/cache: Introduce infrastructure for cache-aware load balancing") Cc: stable@kernel.org #7.2.x Signed-off-by: Chen Yu Signed-off-by: Tim Chen --- kernel/sched/fair.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3e2d236be2a3..341d2f9ed72b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1805,8 +1805,14 @@ void account_mm_sched(struct rq *rq, struct task_struct *p, s64 delta_exec) /* * init_task, kthreads and user thread created * by user_mode_thread() don't have a cache group. - */ - if (!grp || !grp->pcpu_sched) + * In theory a kernel thread does not have any valid + * cache group, because sched_cache_fork() is not + * invoked for a kernel thread - !grp should gate the + * kernel thread. Add the PF_KTHREAD check explicitly + * here for safety reasons, to guard against future + * modifications and to pair with task_tick_cache(). + */ + if (!grp || p->flags & PF_KTHREAD || !grp->pcpu_sched) return; pcpu_sched = per_cpu_ptr(grp->pcpu_sched, cpu_of(rq)); -- 2.32.0