From: zanussi@kernel.org
To: LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>, John Kacur <jkacur@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Daniel Wagner <wagi@monom.org>, Tom Zanussi <zanussi@kernel.org>
Subject: [PATCH RT 10/25] lib/smp_processor_id: Don't use cpumask_equal()
Date: Fri, 21 Feb 2020 15:24:38 -0600 [thread overview]
Message-ID: <369ed4fc17c81f4dddf50babcc39b07a5be7d741.1582320278.git.zanussi@kernel.org> (raw)
In-Reply-To: <cover.1582320278.git.zanussi@kernel.org>
In-Reply-To: <cover.1582320278.git.zanussi@kernel.org>
From: Waiman Long <longman@redhat.com>
v4.14.170-rt75-rc1 stable review patch.
If anyone has any objections, please let me know.
-----------
[ Upstream commit 659252061477862f45b79e1de169e6030f5c8918 ]
The check_preemption_disabled() function uses cpumask_equal() to see
if the task is bounded to the current CPU only. cpumask_equal() calls
memcmp() to do the comparison. As x86 doesn't have __HAVE_ARCH_MEMCMP,
the slow memcmp() function in lib/string.c is used.
On a RT kernel that call check_preemption_disabled() very frequently,
below is the perf-record output of a certain microbenchmark:
42.75% 2.45% testpmd [kernel.kallsyms] [k] check_preemption_disabled
40.01% 39.97% testpmd [kernel.kallsyms] [k] memcmp
We should avoid calling memcmp() in performance critical path. So the
cpumask_equal() call is now replaced with an equivalent simpler check.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
lib/smp_processor_id.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
index 6f4a4ae881c8..9f3c8bb62e57 100644
--- a/lib/smp_processor_id.c
+++ b/lib/smp_processor_id.c
@@ -23,7 +23,7 @@ notrace static unsigned int check_preemption_disabled(const char *what1,
* Kernel threads bound to a single CPU can safely use
* smp_processor_id():
*/
- if (cpumask_equal(current->cpus_ptr, cpumask_of(this_cpu)))
+ if (current->nr_cpus_allowed == 1)
goto out;
/*
--
2.14.1
next prev parent reply other threads:[~2020-02-21 21:26 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 21:24 [PATCH RT 00/25] Linux v4.14.170-rt75-rc1 zanussi
2020-02-21 21:24 ` [PATCH RT 01/25] Fix wrong-variable use in irq_set_affinity_notifier zanussi
2020-02-21 21:24 ` [PATCH RT 02/25] x86: preempt: Check preemption level before looking at lazy-preempt zanussi
2020-02-21 21:24 ` [PATCH RT 03/25] sched/deadline: Ensure inactive_timer runs in hardirq context zanussi
2020-02-24 8:33 ` Sebastian Andrzej Siewior
2020-02-25 14:50 ` Juri Lelli
2020-02-21 21:24 ` [PATCH RT 04/25] i2c: hix5hd2: Remove IRQF_ONESHOT zanussi
2020-02-21 21:24 ` [PATCH RT 05/25] i2c: exynos5: " zanussi
2020-02-21 21:24 ` [PATCH RT 06/25] sched: migrate_dis/enable: Use sleeping_lock…() to annotate sleeping points zanussi
2020-02-21 21:24 ` [PATCH RT 07/25] sched: __set_cpus_allowed_ptr: Check cpus_mask, not cpus_ptr zanussi
2020-02-21 21:24 ` [PATCH RT 08/25] sched: Remove dead __migrate_disabled() check zanussi
2020-02-21 21:24 ` [PATCH RT 09/25] sched: migrate disable: Protect cpus_ptr with lock zanussi
2020-02-21 21:24 ` zanussi [this message]
2020-02-21 21:24 ` [PATCH RT 11/25] futex: Make the futex_hash_bucket spinlock_t again and bring back its old state zanussi
2020-02-21 21:24 ` [PATCH RT 12/25] locking/rtmutex: Clean ->pi_blocked_on in the error case zanussi
2020-02-21 21:24 ` [PATCH RT 13/25] lib/ubsan: Don't seralize UBSAN report zanussi
2020-02-21 21:24 ` [PATCH RT 14/25] kmemleak: Change the lock of kmemleak_object to raw_spinlock_t zanussi
2020-02-21 21:24 ` [PATCH RT 15/25] sched: migrate_enable: Use select_fallback_rq() zanussi
2020-02-24 9:43 ` Sebastian Andrzej Siewior
2020-02-24 15:31 ` Tom Zanussi
2020-02-24 16:05 ` Sebastian Andrzej Siewior
2020-02-24 22:15 ` Scott Wood
2020-02-21 21:24 ` [PATCH RT 16/25] Revert "ARM: Initialize split page table locks for vector page" zanussi
2020-02-21 21:24 ` [PATCH RT 17/25] x86/fpu: Don't cache access to fpu_fpregs_owner_ctx zanussi
2020-02-24 8:55 ` Sebastian Andrzej Siewior
2020-02-24 15:12 ` Tom Zanussi
2020-02-21 21:24 ` [PATCH RT 18/25] locking: Make spinlock_t and rwlock_t a RCU section on RT zanussi
2020-02-21 21:24 ` [PATCH RT 19/25] userfaultfd: Use a seqlock instead of seqcount zanussi
2020-02-24 9:03 ` Sebastian Andrzej Siewior
2020-02-24 15:14 ` Tom Zanussi
2020-02-24 16:17 ` Steven Rostedt
2020-02-21 21:24 ` [PATCH RT 20/25] kmemleak: Cosmetic changes zanussi
2020-02-24 9:12 ` Sebastian Andrzej Siewior
2020-02-24 15:18 ` Tom Zanussi
2020-02-24 15:52 ` Sebastian Andrzej Siewior
2020-02-21 21:24 ` [PATCH RT 21/25] smp: Use smp_cond_func_t as type for the conditional function zanussi
2020-02-24 9:52 ` Sebastian Andrzej Siewior
2020-02-24 15:34 ` Tom Zanussi
2020-02-21 21:24 ` [PATCH RT 22/25] mm/memcontrol: Move misplaced local_unlock_irqrestore() zanussi
2020-02-24 9:55 ` Sebastian Andrzej Siewior
2020-02-21 21:24 ` [PATCH RT 23/25] locallock: Include header for the `current' macro zanussi
2020-02-21 21:24 ` [PATCH RT 24/25] sched: Provide migrate_disable/enable() inlines zanussi
2020-02-21 21:24 ` [PATCH RT 25/25] Linux 4.14.170-rt75-rc1 zanussi
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