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Mon, 8 Jun 2026 18:28:56 +0000 (GMT) Message-ID: <4964b692-36ee-4486-a45a-9b5bfb2ad9bf@linux.ibm.com> Date: Mon, 8 Jun 2026 20:28:56 +0200 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: [PATCH v3 14/20] sched/debug: Provide debugfs to enable/disable steal monitor To: Shrikanth Hegde , linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, yury.norov@gmail.com, kprateek.nayak@amd.com Cc: tglx@kernel.org, gregkh@linuxfoundation.org, pbonzini@redhat.com, seanjc@google.com, vschneid@redhat.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, mgorman@suse.de, bsegall@google.com, maddy@linux.ibm.com, srikar@linux.ibm.com, hdanton@sina.com, chleroy@kernel.org, vineeth@bitbyteword.org, frederic@kernel.org, arighi@nvidia.com, pauld@redhat.com, christian.loehle@arm.com, tj@kernel.org, tommaso.cucinotta@gmail.com, maz@kernel.org, rafael@kernel.org References: <20260514152204.481115-1-sshegde@linux.ibm.com> <20260514152204.481115-15-sshegde@linux.ibm.com> Content-Language: en-US From: Ilya Leoshkevich In-Reply-To: <20260514152204.481115-15-sshegde@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA4MDE3MCBTYWx0ZWRfX8EJzXqeZjhjD icoZS8sCjRH94EraE9TJYEfnY/n8NLlPYjRLtzixP3lkuN8ZHDOgjp3aEaQM+ix6QZ4bauaRzkY QLwRgcHrHEA1r9NA01UyiexLHK+hQW60ovo307tPg2bYwmZc3Ux9f/YWp9c0y+3pZF4I8u5EZBU J+uug30fVifPMETghQa0EfocQzlOuZJQUEVJyZzrE8rYgkJ1kRjNGUDIajrUxYC02N7qvhVBdET zHh4fddcjQSipNMWoXy/F4jv5GFjVDGlWvGUh6xdhdQ5MNjwwNMA0mE2plS8WScagfaG0rf1lFm Z6mfhC1GXHOQLm2C3oWHmuboLgorZ3IgntzTL1rdYhe96hPOK1EUWb18AwQ9jSLkpYeuLgYbkRD Hidmrswg72CB0tvEb0b3w9veDuRMb7GS9eLFuIcqbenUOWwFiAXewiVDkIaAMco6UNz5KSJSpn9 2/cyk6H/GgHhGk0icEA== X-Authority-Analysis: v=2.4 cv=QKhYgALL c=1 sm=1 tr=0 ts=6a2709ef cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=_UOBtEWHNwjfI8wcr-AA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: I1ccJwRd2bFgK9hyNhwfoPyke0SgRt71 X-Proofpoint-ORIG-GUID: 4vI33q-9sbTJkz181mPGoXErZ6zxpOaA X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-08_04,2026-06-05_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 suspectscore=0 spamscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606080170 On 5/14/26 17:21, Shrikanth Hegde wrote: > Add a debugfs "enable" file to enable steal time monitor. > > Computing steal time and acting on it periodically are to be opted by > the user. This helps to avoid any overhead when the feature > is disabled. > > It is disabled by default. > > Signed-off-by: Shrikanth Hegde > --- > kernel/sched/core.c | 1 + > kernel/sched/debug.c | 29 +++++++++++++++++++++++++++++ > kernel/sched/sched.h | 2 ++ > 3 files changed, 32 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 0d1995c65ce6..1533a44d1a6b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c [...] > @@ -592,6 +592,33 @@ static void debugfs_ext_server_init(void) > #endif /* CONFIG_SCHED_CLASS_EXT */ > > #ifdef CONFIG_PREFERRED_CPU > +__read_mostly bool sched_sm_wr_enable; > + > +static ssize_t sched_sm_en_write(struct file *filp, const char __user *ubuf, > + size_t cnt, loff_t *ppos) > +{ > + bool orig = sched_sm_wr_enable; > + ssize_t result; > + > + result = debugfs_write_file_bool(filp, ubuf, cnt, ppos); > + > + if (sched_sm_wr_enable && !orig) { > + static_branch_enable(&__sched_sm_enable); Would it make sense to clear the steal monitor state when enabling it? Otherwise we may immediately trigger a bogus "dec" if user did a disable during contention and re-enabled when everything is quiet. [...]