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Wed, 6 May 2026 11:01:21 +0000 (GMT) From: Shrikanth Hegde To: mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org Cc: sshegde@linux.ibm.com, kprateek.nayak@amd.com, juri.lelli@redhat.com, vschneid@redhat.com, dietmar.eggemann@arm.com, tj@kernel.org, rostedt@goodmis.org, tglx@kernel.org, mgorman@suse.de, bsegall@google.com, arighi@nvidia.com Subject: [PATCH 3/3] sched/fair: Add compile time check in fastpaths for CONFIG_SCHED_SMT=n Date: Wed, 6 May 2026 16:30:52 +0530 Message-ID: <20260506110052.9974-4-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260506110052.9974-1-sshegde@linux.ibm.com> References: <20260506110052.9974-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA2MDEwNCBTYWx0ZWRfX0JU8ZEAJ1T1a xB9eEgHePSz6R6GLjdu1xaamtWkhhbS5PJY69gwpK0IxyGOVxMONBEYqZMDPvtcNcXM27HyX0Dv DuB41R3CC3la3T/i70WyTUdgGyZNoyiHtDxheieXei9mwJnEiti3juONhn8QvO9Vx0VomH3aD8i eZwRoLh+pIEnFN8wcnoqhAvwxN9At0QXIYsmL6FiLbbLR1crQLKlk4YumsAcTaHukg4naMTlxiG aOAinXW4Ut51YZmZacJYtudzTzO06aMoPQJxUJzP+WAkxoLYTz4owtt15N6BLWudYrl75g9HksT ij8znVV1mJCtvI5GfYsZkkaDmkuOorY2g3RplBzcwvUJiZwcrwReSSGwVW9yIiDSlHCZxFbzBWj icWsKHapGqVPPD40KbkLwpBwOQOvASr9Kc6Ah52nFhSxO86+RtMqtX6cyVAzyEiAVf8I/o4appY hEOTeNoWIbRvufugtug== X-Proofpoint-ORIG-GUID: WbNwmElGMBoj2uVufk8E8x5NFFGmMnLx X-Proofpoint-GUID: _MDHuzSVOHhi-Vpno1BDwNrEatdXF0sY X-Authority-Analysis: v=2.4 cv=ctWrVV4i c=1 sm=1 tr=0 ts=69fb1f8a cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=tAA0q8KrAMZJwkcq1PQA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-05_03,2026-04-30_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 clxscore=1015 suspectscore=0 impostorscore=0 spamscore=0 malwarescore=0 phishscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605060104 For fastpaths such as wakeup, load balance even a minimal code additons can pop up. Add IS_ENABLED checks there to ensure there is no overhead. Other places are either have sched_smt_active() check or they are not in fast paths. Signed-off-by: Shrikanth Hegde --- kernel/sched/fair.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d19c416d1b84..cdd7f9633f98 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1557,6 +1557,9 @@ static inline bool is_core_idle(int cpu) { int sibling; + if (!IS_ENABLED(CONFIG_SCHED_SMT)) + return true; + for_each_cpu(sibling, cpu_smt_mask(cpu)) { if (cpu == sibling) continue; @@ -11973,7 +11976,8 @@ static int should_we_balance(struct lb_env *env) * idle has been found, then its not needed to check other * SMT siblings for idleness: */ - cpumask_andnot(swb_cpus, swb_cpus, cpu_smt_mask(cpu)); + if (IS_ENABLED(CONFIG_SCHED_SMT)) + cpumask_andnot(swb_cpus, swb_cpus, cpu_smt_mask(cpu)); continue; } -- 2.51.0