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Tue, 12 May 2026 15:21:43 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.39.28.106]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 12 May 2026 15:21:43 +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, mgorman@suse.de, bsegall@google.com, arighi@nvidia.com Subject: [PATCH v2 3/3] sched/fair: Add compile time check in fastpaths for CONFIG_SCHED_SMT=n Date: Tue, 12 May 2026 20:51:25 +0530 Message-ID: <20260512152125.308280-4-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260512152125.308280-1-sshegde@linux.ibm.com> References: <20260512152125.308280-1-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-Authority-Analysis: v=2.4 cv=Y/XIdBeN c=1 sm=1 tr=0 ts=6a03458e cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=tAA0q8KrAMZJwkcq1PQA:9 X-Proofpoint-GUID: P-lzklsQSKRqacvYNSVgJhenAholtj-z X-Proofpoint-ORIG-GUID: 48XEqWcWu3I5gzokjQXme8bNrlHrNpEd X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTEyMDE1OCBTYWx0ZWRfXzMXPUkAGbHFS vcrwjVa/7rwQ289Hbn/OLicE8nlJtar/dTDFL2E4E0E48VIg2D0TrpIhYmvJaz/fLI8RoaFzEWf bpbWLWSM++X0C096UPgRgZmA12wABP2IMsNYsA24zElG+ByBH7Lml0UYFIuv2rXRgGpu5fpBbFC 5Uwb2446JYfwMESrjiN3Zh2yBvbh72VLobzS00aJDdYjAInnpf31Sp9pXe0kfLHVBFXy9Z9VpIM nGjZwMdr+Qlcwe1eqRw8qLRRZiXFAjY6GlG+ILh/KdB/Pz0FPO3SjV/PhZI3c5UDwq3rLnHDrFq eNwi/vIcaonKyqbvFl1XBpvmgqZ6QMd3i/dZvnLZFRhn1wVa6LUafob9kfKHkCaUzkndhHGKifs 93JvpXSB7RcEc2iC7/jG499ZrRoCElI3LKp2vxH6QLI8O93W8KWB9I3YRNNpH/DgZo1M/guWt8M 75Ne3Zucw12E9Bsv6Rw== 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=2026-05-11_05,2026-05-08_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 phishscore=0 malwarescore=0 suspectscore=0 bulkscore=0 spamscore=0 adultscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605050000 definitions=main-2605120158 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 353e31ecaadc..b6f9592b31fd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1586,6 +1586,9 @@ 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; @@ -12003,7 +12006,8 @@ 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; } -- 2.47.3