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([124.93.80.37]) by smtp.googlemail.com with ESMTPSA id 41be03b00d2f7-ba900fa571esm10913877a12.26.2025.11.09.19.32.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 09 Nov 2025 19:32:42 -0800 (PST) From: Wanpeng Li To: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Paolo Bonzini , Sean Christopherson Cc: Steven Rostedt , Vincent Guittot , Juri Lelli , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Wanpeng Li Subject: [PATCH 01/10] sched: Add vCPU debooster infrastructure Date: Mon, 10 Nov 2025 11:32:22 +0800 Message-ID: <20251110033232.12538-2-kernellwp@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251110033232.12538-1-kernellwp@gmail.com> References: <20251110033232.12538-1-kernellwp@gmail.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 From: Wanpeng Li From: Wanpeng Li Introduce foundational infrastructure for the vCPU debooster mechanism to improve yield_to() effectiveness in virtualization workloads. Add per-rq tracking fields for rate limiting (yield_deboost_last_time_ns) and debouncing (yield_deboost_last_src/dst_pid, last_pair_time_ns). Introduce global sysctl knob sysctl_sched_vcpu_debooster_enabled for runtime control, defaulting to enabled. Add debugfs interface for observability and initialization in sched_init(). The infrastructure is inert at this stage as no deboost logic is implemented yet, allowing independent verification that existing behavior remains unchanged. Signed-off-by: Wanpeng Li --- kernel/sched/core.c | 7 +++++-- kernel/sched/debug.c | 3 +++ kernel/sched/fair.c | 5 +++++ kernel/sched/sched.h | 9 +++++++++ 4 files changed, 22 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f754a60de848..03380790088b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8706,9 +8706,12 @@ void __init sched_init(void) #endif /* CONFIG_CGROUP_SCHED */ for_each_possible_cpu(i) { - struct rq *rq; + struct rq *rq = cpu_rq(i); + /* init per-rq debounce tracking */ + rq->yield_deboost_last_src_pid = -1; + rq->yield_deboost_last_dst_pid = -1; + rq->yield_deboost_last_pair_time_ns = 0; - rq = cpu_rq(i); raw_spin_lock_init(&rq->__lock); rq->nr_running = 0; rq->calc_load_active = 0; diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 02e16b70a790..905f303af752 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -508,6 +508,9 @@ static __init int sched_init_debug(void) debugfs_create_file("tunable_scaling", 0644, debugfs_sched, NULL, &sched_scaling_fops); debugfs_create_u32("migration_cost_ns", 0644, debugfs_sched, &sysctl_sched_migration_cost); debugfs_create_u32("nr_migrate", 0644, debugfs_sched, &sysctl_sched_nr_migrate); + debugfs_create_u32("sched_vcpu_debooster_enabled", 0644, debugfs_sched, + &sysctl_sched_vcpu_debooster_enabled); + sched_domains_mutex_lock(); update_sched_domain_debugfs(); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5b752324270b..5b7fcc86ccff 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -81,6 +81,11 @@ static unsigned int normalized_sysctl_sched_base_slice = 700000ULL; __read_mostly unsigned int sysctl_sched_migration_cost = 500000UL; +/* + * vCPU debooster sysctl control + */ +unsigned int sysctl_sched_vcpu_debooster_enabled __read_mostly = 1; + static int __init setup_sched_thermal_decay_shift(char *str) { pr_warn("Ignoring the deprecated sched_thermal_decay_shift= option\n"); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index adfb6e3409d7..e9b4be024f89 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1292,6 +1292,13 @@ struct rq { unsigned int push_busy; struct cpu_stop_work push_work; + /* vCPU debooster rate-limit */ + u64 yield_deboost_last_time_ns; + /* per-rq debounce state to avoid cross-CPU races */ + pid_t yield_deboost_last_src_pid; + pid_t yield_deboost_last_dst_pid; + u64 yield_deboost_last_pair_time_ns; + #ifdef CONFIG_SCHED_CORE /* per rq */ struct rq *core; @@ -2816,6 +2823,8 @@ extern int sysctl_resched_latency_warn_once; extern unsigned int sysctl_sched_tunable_scaling; +extern unsigned int sysctl_sched_vcpu_debooster_enabled; + extern unsigned int sysctl_numa_balancing_scan_delay; extern unsigned int sysctl_numa_balancing_scan_period_min; extern unsigned int sysctl_numa_balancing_scan_period_max; -- 2.43.0