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Tue, 9 Jun 2026 05:04:17 +0000 (GMT) Message-ID: <94324f96-dc1a-4010-99af-391068bb0498@linux.ibm.com> Date: Tue, 9 Jun 2026 10:34:16 +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: [PATCH v3 14/20] sched/debug: Provide debugfs to enable/disable steal monitor To: Ilya Leoshkevich , 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> <4964b692-36ee-4486-a45a-9b5bfb2ad9bf@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <4964b692-36ee-4486-a45a-9b5bfb2ad9bf@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=HppG3UTS c=1 sm=1 tr=0 ts=6a279ede 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=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=3DX3vuG933DJuKA4uFMA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: bLFYOxbeewmb6zz6CTSGMTJdNXsmc6U3 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA5MDAzOSBTYWx0ZWRfX5v3pUQ5MVEvf DELzawuasuqKv+O6xNSBmJ4mG6m5ZIr7U3GppwAmkMBITBqI20ulaqb8dqpfwtm1iTEo90Zeniq bk2vAPBziVAVKgD3C02FtJx4P7BsFGCTOGGAXEM6guJQQZnszH9K2Ev4fbWJL5j7E9l6GBW3R6j kaKSW82XXpPCc3Y8LLmrgOfSSZdcZRqxKWtNOqEtfw0nNdvrOhzshEwxS5+Rnq7rBSR3YTeyCHX BYZ6qGer4Fqp0kDjg16ojtt8xcoDD1u8WHcw808y7LtEM8Ny95E5lBVQJGZtfNvfdFEpLklZbv/ 1dYn22HlbodmDNKj20HP+ZazQexO9nz/68ad3dacEuHZzxpjnNx5t+afHoNqGE34CVtP6LrfhVp 1TKxoPUB0nq2sVDmWripICLaj2dU8FOrB6JozjslFsBqAEbN2PKDJZOhCoefUdb4jCLX9waWg6X NRzNmKY8VLkwWH8WblA== X-Proofpoint-ORIG-GUID: LV2q4rHS27JgGBr07rKTQWDeulUh2aqk 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=2026-06-09_01,2026-06-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606090039 On 6/8/26 11:58 PM, Ilya Leoshkevich wrote: > > > 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. > Yes, it may lead to one wrong direction decision but for the case when disable was during contention and re-enabled again during contention. I think setting previous_decision = 0 during disable to should fix it. So previous direction of inc/dec won't carry over the enable.