From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.246 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793869523; b=1QrgvB+KLMd6qwlmXixd1jzL49H1FRLY0/9+DDbAoNoYv9wGDkeU/1o33TIEkfaWZzey JlJrKq2ypT94WYi+JcTIJz7oEW38LLxj2ma0DcPL2DeGemw3rCC3Kc3LMaVZoKYIC2Sbh o7jaGdxYVQCiyCEH0DBxwD/xYDagN8mGuH67Yx0pOsGe9XvXaYCL8oE5LAr4AG26LSmDd gMl6Ndae7GlsAzP1zb6uWXWqWamQlm1nUGHpTdwOlQDfDKCiWZ9KfqBd0PWD+fUBe+BaB fLDOX6UCNFICtz+Ao4p9tbKS+ok+a4Uo4bjbwwtsBUz/UEpivWxDI91EbE0Nf6XojIw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793869523; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-Id: X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=tyXT3V1giPULzTli43gvYizMlTh6ps7zNGmY3FWZQOM=; b=q0iOQus2NO3CwD7bToDrdr853qSDngH4ukvynaXJKlyPrXSU40zeyRvL6Xu/82rjLmmj u+oGK8XQiXQJ/x3YKvL7DJgOI/hdVCwyk2sc8nBqCZ6mn2WzzrjJUR7o3vUSnJcJKjMUA kzV5Ttv5KUKG1sd937Zu+mfZr6Q7iBw1f1iCoEOXoDifNE2K5IGnJEzMttKSZXHKYGpXF E99CrM8HH50uMyGI2Uo43OAyXUyiEu58BAUlm+zrdgDpWO4SKmjhw52wLTnu36gXreyau ePrsTfdd1WYPQC0kCV/WKBoH3Ds+MGhI8ldSHz7UtgnpTbPcDOUoJEHI9r/0mDEkykQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=RzjBhvaz; arc=none smtp.remote-ip=91.218.175.246 Received: from mta0.migadu.com (out-246.mta0.migadu.com [91.218.175.246]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D8041606A31B for ; Thu, 5 Nov 2026 09:05:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org D8041606A31B Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=RzjBhvaz X-Envelope-To: linux-doc@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=UGrLw7tJ8SzIUnajBIKmwWZs/FFny8I1ZQMJWZrsm+Q=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793869521; v=1; x=1794474321; b=RzjBhvazzFCPfHMBqevNsz5QvRylEPRwFm09vjeAAQVIKtcKwUMAMkkZDdR3zHLdeDf122KC DviCH0q1X0zIwTQAeAipZ/8Rpll201Rw9hI96e+HDK1mVm0BZfvhg7vHm5OVYuUx30kptnlWJIj apw9ZRKcxU05v7D7pR9otVig= X-Envelope-To: linux-doc@vger.kernel.org Received: by mta11.migadu.com with ESMTPS id 8f2b4df41c8b103c; Thu, 05 Nov 2026 09:05:17 +0000 X-Mizu-Trace-ID: 8f2b4df41c8b103c X-Migadu-Flow: FLOW_OUT From: Fushuai Wang To: ynorov@nvidia.com Cc: agordeev@linux.ibm.com, arighi@nvidia.com, borntraeger@linux.ibm.com, bsegall@google.com, corbet@lwn.net, dakr@kernel.org, dietmar.eggemann@arm.com, driver-core@lists.linux.dev, gor@linux.ibm.com, gregkh@linuxfoundation.org, hca@linux.ibm.com, johan@kernel.org, juri.lelli@redhat.com, kprateek.nayak@amd.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux@rasmusvillemoes.dk, meted@linux.ibm.com, mgorman@suse.de, mingo@redhat.com, peterz@infradead.org, rafael@kernel.org, rdunlap@infradead.org, rostedt@goodmis.org, skhan@linuxfoundation.org, sshegde@linux.ibm.com, svens@linux.ibm.com, tglx@kernel.org, vincent.guittot@linaro.org, vschneid@redhat.com, yury.norov@gmail.com Subject: Re: [PATCH 3/6] sched: Restore preferred CPUs when hotplug removes the last one Date: Thu, 5 Nov 2026 17:05:05 +0800 Message-Id: <20261105090505.93940-1-fushuai.wang@linux.dev> X-Mailer: git-send-email 2.39.2 (Apple Git-143) In-Reply-To: <20261101192203.6979-4-ynorov@nvidia.com> References: <20261101192203.6979-4-ynorov@nvidia.com> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 04b62c16fa8c..98f4f9434965 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -8712,6 +8712,14 @@ int sched_cpu_deactivate(unsigned int cpu) > > set_cpu_active(cpu, false); > > +#ifdef CONFIG_PREFERRED_CPU > + if (cpumask_empty(cpu_preferred_mask)) { > + pr_notice("sched: last preferred CPU%u offlined; make all active CPUs preferred\n", > + cpu); > + reset_preferred_cpumask(); Hi, Yury If the CPU being offlined is the only preferred CPU, after reset_preferred_cpumask(), the steal governor may still need some time to tighten the mask again, and eventually only one preferred CPU may remain. Would this introduce additional task migration overhead? Regards, Fushuai. > + } > +#endif > + > /* > * From this point forward, this CPU will refuse to run any task that > * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively