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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b4722e9c1basm435239a12.5.2025.08.14.07.01.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Aug 2025 07:01:46 -0700 (PDT) From: Zhongqiu Han To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Cc: linux-kernel@vger.kernel.org, quic_zhonhan@quicinc.com, zhongqiu.han@oss.qualcomm.com Subject: [PATCH] sched/fair: Save cpu id locally to avoid repeated smp_processor_id() calls Date: Thu, 14 Aug 2025 22:01:41 +0800 Message-ID: <20250814140141.2655087-1-zhongqiu.han@oss.qualcomm.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODExMDA3NCBTYWx0ZWRfXz9TJ6VOFlJUW G0WtT/ufGfGZFbZr+hefZ7wjH0qfyHoxDu2+MZ0z3u8qekRbKcu/9j1aTlYvY5XeW+XKJL98Wb0 UGkmrMbZO8d0lUb0g3BwYyFJ++X3BN37VMH1tr8mRjAhtyNxW4/7adzdn7jBKJfpg2pzNfOFfXe nXdX6ACpz1AeeCjvCeMaZrpYWbsqFM1Z5WugiTE3RqT1a3YhF8OF+stnJUEo+i97tLDHsZTrjX9 hWJKE3elDDYvEySejczVSWaP6kUp5N/pGAJzr5EUYn/qmLgu36hLaNcBf8IkLKxB8knoT+mJ8LF 7qtNipiZReU78NGAYJtRJKfJwyDY2JLuf8C+iRV18T/vgcPU3sylumUf8byBZHXTCo300qbcV1a mUQECzsA X-Proofpoint-GUID: v6_OgD0fNBWLPkDVGY30uwMWBzs1YA17 X-Authority-Analysis: v=2.4 cv=TJFFS0la c=1 sm=1 tr=0 ts=689dec50 cx=c_pps a=m5Vt/hrsBiPMCU0y4gIsQw==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=2OwXVqhp2XgA:10 a=EUspDBNiAAAA:8 a=so28Ua-aKlcwq8TSCoQA:9 a=IoOABgeZipijB_acs4fv:22 X-Proofpoint-ORIG-GUID: v6_OgD0fNBWLPkDVGY30uwMWBzs1YA17 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-13_02,2025-08-14_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 adultscore=0 impostorscore=0 malwarescore=0 phishscore=0 clxscore=1011 spamscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508110074 Content-Type: text/plain; charset="utf-8" Avoid repeated smp_processor_id() by saving cpu id in a local variable. - find_new_ilb(): func called with interrupts disabled. - sched_cfs_period_timer(): cpu id saved after raw_spin_lock_irqsave(). This improves clarity and reduces overhead without changing functionality. Signed-off-by: Zhongqiu Han --- kernel/sched/fair.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e256793b9a08..60a9830fb8a4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6401,6 +6401,8 @@ static enum hrtimer_restart sched_cfs_period_timer(st= ruct hrtimer *timer) int count =3D 0; =20 raw_spin_lock_irqsave(&cfs_b->lock, flags); + int cpu =3D smp_processor_id(); + for (;;) { overrun =3D hrtimer_forward_now(timer, cfs_b->period); if (!overrun) @@ -6424,13 +6426,13 @@ static enum hrtimer_restart sched_cfs_period_timer(= struct hrtimer *timer) =20 pr_warn_ratelimited( "cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us= =3D %lld, cfs_quota_us =3D %lld)\n", - smp_processor_id(), + cpu, div_u64(new, NSEC_PER_USEC), div_u64(cfs_b->quota, NSEC_PER_USEC)); } else { pr_warn_ratelimited( "cfs_period_timer[cpu%d]: period too short, but cannot scale up without l= osing precision (cfs_period_us =3D %lld, cfs_quota_us =3D %lld)\n", - smp_processor_id(), + cpu, div_u64(old, NSEC_PER_USEC), div_u64(cfs_b->quota, NSEC_PER_USEC)); } @@ -12195,12 +12197,13 @@ static inline int find_new_ilb(void) { const struct cpumask *hk_mask; int ilb_cpu; + int this_cpu =3D smp_processor_id(); =20 hk_mask =3D housekeeping_cpumask(HK_TYPE_KERNEL_NOISE); =20 for_each_cpu_and(ilb_cpu, nohz.idle_cpus_mask, hk_mask) { =20 - if (ilb_cpu =3D=3D smp_processor_id()) + if (ilb_cpu =3D=3D this_cpu) continue; =20 if (idle_cpu(ilb_cpu)) --=20 2.43.0