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[23.118.52.46]) by smtp.gmail.com with ESMTPSA id v1sm3283176pjg.19.2021.07.08.12.46.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jul 2021 12:46:44 -0700 (PDT) From: Peter Oskolkov X-Google-Original-From: Peter Oskolkov To: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Cc: Paul Turner , Ben Segall , Peter Oskolkov , Peter Oskolkov , Joel Fernandes , Andrei Vagin , Jim Newsome , Jann Horn Subject: [RFC PATCH 1/3 v0.2] sched: add WF_CURRENT_CPU and externise ttwu Date: Thu, 8 Jul 2021 12:46:36 -0700 Message-Id: <20210708194638.128950-2-posk@google.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210708194638.128950-1-posk@google.com> References: <20210708194638.128950-1-posk@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add WF_CURRENT_CPU wake flag that advices the scheduler to move the wakee to the current CPU. This is useful for fast on-CPU context switching use cases such as UMCG. In addition, make ttwu external rather than static so that the flag could be passed to it from outside of sched/core.c. Signed-off-by: Peter Oskolkov --- kernel/sched/core.c | 3 +-- kernel/sched/fair.c | 4 ++++ kernel/sched/sched.h | 15 +++++++++------ 3 files changed, 14 insertions(+), 8 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0c22cd026440..293f5801bf81 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3680,8 +3680,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * Return: %true if @p->state changes (an actual wakeup was done), * %false otherwise. */ -static int -try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) +int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) { unsigned long flags; int cpu, success = 0; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 11d22943753f..16a9c93e6e82 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6836,6 +6836,10 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) if (wake_flags & WF_TTWU) { record_wakee(p); + if ((wake_flags & WF_CURRENT_CPU) && + cpumask_test_cpu(cpu, p->cpus_ptr)) + return cpu; + if (sched_energy_enabled()) { new_cpu = find_energy_efficient_cpu(p, prev_cpu); if (new_cpu >= 0) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 9a1c6aeb9165..80de6836f8ae 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2031,13 +2031,14 @@ static inline int task_on_rq_migrating(struct task_struct *p) } /* Wake flags. The first three directly map to some SD flag value */ -#define WF_EXEC 0x02 /* Wakeup after exec; maps to SD_BALANCE_EXEC */ -#define WF_FORK 0x04 /* Wakeup after fork; maps to SD_BALANCE_FORK */ -#define WF_TTWU 0x08 /* Wakeup; maps to SD_BALANCE_WAKE */ +#define WF_EXEC 0x02 /* Wakeup after exec; maps to SD_BALANCE_EXEC */ +#define WF_FORK 0x04 /* Wakeup after fork; maps to SD_BALANCE_FORK */ +#define WF_TTWU 0x08 /* Wakeup; maps to SD_BALANCE_WAKE */ -#define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */ -#define WF_MIGRATED 0x20 /* Internal use, task got migrated */ -#define WF_ON_CPU 0x40 /* Wakee is on_cpu */ +#define WF_SYNC 0x10 /* Waker goes to sleep after wakeup */ +#define WF_MIGRATED 0x20 /* Internal use, task got migrated */ +#define WF_ON_CPU 0x40 /* Wakee is on_cpu */ +#define WF_CURRENT_CPU 0x80 /* Prefer to move the wakee to the current CPU. */ #ifdef CONFIG_SMP static_assert(WF_EXEC == SD_BALANCE_EXEC); @@ -3037,6 +3038,8 @@ static inline bool is_per_cpu_kthread(struct task_struct *p) extern void swake_up_all_locked(struct swait_queue_head *q); extern void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait); +extern int try_to_wake_up(struct task_struct *tsk, unsigned int state, int wake_flags); + #ifdef CONFIG_PREEMPT_DYNAMIC extern int preempt_dynamic_mode; extern int sched_dynamic_mode(const char *str); -- 2.25.1