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Mon, 23 Jun 2025 08:10:06 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0728F20043; Mon, 23 Jun 2025 08:10:06 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 24CEE2006E; Mon, 23 Jun 2025 08:10:03 +0000 (GMT) Received: from [9.109.215.252] (unknown [9.109.215.252]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 23 Jun 2025 08:10:02 +0000 (GMT) Message-ID: Date: Mon, 23 Jun 2025 13:40:00 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/5] cpumask: Introduce cpu parked mask To: Yury Norov , peterz@infradead.org Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, tglx@linutronix.de, maddy@linux.ibm.com, vschneid@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, jstultz@google.com, kprateek.nayak@amd.com, huschle@linux.ibm.com, srikar@linux.ibm.com, linux-kernel@vger.kernel.org, linux@rasmusvillemoes.dk References: <20250523181448.3777233-1-sshegde@linux.ibm.com> <20250523181448.3777233-2-sshegde@linux.ibm.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjIzMDA0NSBTYWx0ZWRfX4tq3AsMQL8z6 kaDVsrK3HcyBzHjoj7mpjlMglO/WVNYhzLdTzyFGxK46fXSAiya0RUJd1u+m7eiegRD1LbCWXCg ZRSQvbRkkmAHLYncU8QaAeQmYAtUdVj/UIx8IRg97g5NkrvoF7WhnymZ9qSIwd/uy4tRz7X1fkV lTLIZQxlKNp16yVe540E9L0Jkg5Jz5C/w9Prp7nnI5frkgDKougSlerNi2C4sz+UZa8zJACg2Bp jH+i+7IYUfuFnDmgR5LnPCLtirjInDiDBoce1nuJQaBPL6H/xJmpb2SiQDSY4T2Eu5J27RNUndX ClyK/hQ14fIT3LkFeJgQIhhFA/uFhO6VSt1DZQvRMhGNKSEcTOVt6YAt1QzDdQMYEvJ28ozJHf8 3ThRqt2oAn0p6R4b/qJWPYas7BmL+QV7JRSR0wMrKOB35eXKVzdAlBKcmUcXR1DrvNOKGvbE X-Proofpoint-GUID: mLLm86scRAN6AfYW4oe3FU6yVKA9Dxw0 X-Proofpoint-ORIG-GUID: S7c8spHF4EtvPrYPzD7mV-ac27n6-PCg X-Authority-Analysis: v=2.4 cv=combk04i c=1 sm=1 tr=0 ts=68590be4 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=6IFa9wvqVegA:10 a=W0WVT37j5QbsdxkpU7oA:9 a=QEXdDO2ut3YA:10 a=zZCYzV9kfG8A:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-06-23_02,2025-06-20_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 spamscore=0 adultscore=0 mlxlogscore=772 clxscore=1015 impostorscore=0 suspectscore=0 mlxscore=0 phishscore=0 lowpriorityscore=0 bulkscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2506230045 On 5/27/25 20:36, Yury Norov wrote: > On Fri, May 23, 2025 at 11:44:44PM +0530, Shrikanth Hegde wrote: >> CPU is said to be parked, when underlying physical CPU is not >> available. This happens when there is contention for CPU resource in >> para-virtualized case. One should avoid using these CPUs. >> >> Build and maintain this state of parked CPUs. Scheduler will use this >> information and push the tasks out as soon as it can. > > This 'parked' term sounds pretty obscured. Maybe name it in > a positive sense, and more explicit, like cpu_paravirt_mask. > I still dont know a better name. Maybe something like cpu_avoid_mask and cpu avoid(cpu)? I would like to retain a notion that these CPU shouldn't be used at the moment. > Also, shouldn't this be conditional on CONFIG_PARAVIRT? > I moved the uses of it under a static key which should make it a nop for others. That keeps code relatively simpler. Hope that's ok. > Thanks, > Yury >