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2025-01-06sched_ext: update scx_bpf_dsq_insert() doc for SCX_DSQ_LOCAL_ONAndrea Righi
With commit 5b26f7b920f7 ("sched_ext: Allow SCX_DSQ_LOCAL_ON for direct dispatches"), scx_bpf_dsq_insert() can use SCX_DSQ_LOCAL_ON for direct dispatch from ops.enqueue() to target the local DSQ of any CPU. Update the documentation accordingly. Fixes: 5b26f7b920f7 ("sched_ext: Allow SCX_DSQ_LOCAL_ON for direct dispatches") Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2025-01-06sched_ext: idle: small CPU iteration refactoringAndrea Righi
Replace the loop to check if all SMT CPUs are idle with cpumask_subset(). This simplifies the code and slightly improves efficiency, while preserving the original behavior. Note that idle_masks.smt handling remains racy, which is acceptable as it serves as an optimization and is self-correcting. Suggested-and-reviewed-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2025-01-03Merge tag 'sched_ext-for-6.13-rc5-fixes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext Pull sched_ext fixes from Tejun Heo: - Fix a bug where bpf_iter_scx_dsq_new() was not initializing the iterator's flags and could inadvertently enable e.g. reverse iteration - Fix a bug where scx_ops_bypass() could call irq_restore twice - Add Andrea and Changwoo as maintainers for better review coverage - selftests and tools/sched_ext build and other fixes * tag 'sched_ext-for-6.13-rc5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: sched_ext: Fix dsq_local_on selftest sched_ext: initialize kit->cursor.flags sched_ext: Fix invalid irq restore in scx_ops_bypass() MAINTAINERS: add me as reviewer for sched_ext MAINTAINERS: add self as reviewer for sched_ext scx: Fix maximal BPF selftest prog sched_ext: fix application of sizeof to pointer selftests/sched_ext: fix build after renames in sched_ext API sched_ext: Add __weak to fix the build errors
2024-12-29sched_ext: idle: introduce check_builtin_idle_enabled() helperAndrea Righi
Minor refactoring to add a helper function for checking if the built-in idle CPU selection policy is enabled. Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-29sched_ext: idle: clarify commentsAndrea Righi
Add a comments to clarify about the usage of cpumask_intersects(). Moreover, update scx_select_cpu_dfl() description clarifying that the final step of the idle selection logic involves searching for any idle CPU in the system that the task can use. Reviewed-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-29sched_ext: idle: use assign_cpu() to update the idle cpumaskAndrea Righi
Use the assign_cpu() helper to set or clear the CPU in the idle mask, based on the idle condition. Acked-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-24sched_ext: initialize kit->cursor.flagsHenry Huang
struct bpf_iter_scx_dsq *it maybe not initialized. If we didn't call scx_bpf_dsq_move_set_vtime and scx_bpf_dsq_move_set_slice before scx_bpf_dsq_move, it would cause unexpected behaviors: 1. Assign a huge slice into p->scx.slice 2. Assign a invalid vtime into p->scx.dsq_vtime Signed-off-by: Henry Huang <henry.hj@antgroup.com> Fixes: 6462dd53a260 ("sched_ext: Compact struct bpf_iter_scx_dsq_kern") Cc: stable@vger.kernel.org # v6.12 Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-24sched_ext: Use str_enabled_disabled() helper in update_selcpu_topology()Thorsten Blum
Remove hard-coded strings by using the str_enabled_disabled() helper function. Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev> Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-23Merge back earlier cpufreq material for 6.14Rafael J. Wysocki
2024-12-20docs: Update Schedstat version to 17Swapnil Sapkal
Update the Schedstat version to 17 as more fields are added to report different kinds of imbalances in the sched domain. Also domain field started printing corresponding domain name. Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20241220063224.17767-7-swapnil.sapkal@amd.com
2024-12-20sched/stats: Print domain name in /proc/schedstatK Prateek Nayak
Currently, there does not exist a straightforward way to extract the names of the sched domains and match them to the per-cpu domain entry in /proc/schedstat other than looking at the debugfs files which are only visible after enabling "verbose" debug after commit 34320745dfc9 ("sched/debug: Put sched/domains files under the verbose flag") Since tools like `perf sched stats`[1] require displaying per-domain information in user friendly manner, display the names of sched domain, alongside their level in /proc/schedstat. Domain names also makes the /proc/schedstat data unambiguous when some of the cpus are offline. For example, on a 128 cpus AMD Zen3 machine where CPU0 and CPU64 are SMT siblings and CPU64 is offline: Before: cpu0 ... domain0 ... domain1 ... cpu1 ... domain0 ... domain1 ... domain2 ... After: cpu0 ... domain0 MC ... domain1 PKG ... cpu1 ... domain0 SMT ... domain1 MC ... domain2 PKG ... [1] https://lore.kernel.org/lkml/20241122084452.1064968-1-swapnil.sapkal@amd.com/ Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com> Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: James Clark <james.clark@linaro.org> Link: https://lore.kernel.org/r/20241220063224.17767-6-swapnil.sapkal@amd.com
2024-12-20sched: Move sched domain name out of CONFIG_SCHED_DEBUGSwapnil Sapkal
/proc/schedstat file shows cpu and sched domain level scheduler statistics. It does not show domain name instead shows domain level. It will be very useful for tools like `perf sched stats`[1] to aggragate domain level stats if domain names are shown in /proc/schedstat. But sched domain name is guarded by CONFIG_SCHED_DEBUG. As per the discussion[2], move sched domain name out of CONFIG_SCHED_DEBUG. [1] https://lore.kernel.org/lkml/20241122084452.1064968-1-swapnil.sapkal@amd.com/ [2] https://lore.kernel.org/lkml/fcefeb4d-3acb-462d-9c9b-3df8d927e522@amd.com/ Suggested-by: "Gautham R. Shenoy" <gautham.shenoy@amd.com> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20241220063224.17767-5-swapnil.sapkal@amd.com
2024-12-20sched: Report the different kinds of imbalances in /proc/schedstatSwapnil Sapkal
In /proc/schedstat, lb_imbalance reports the sum of imbalances discovered in sched domains with each call to sched_balance_rq(), which is not very useful because lb_imbalance does not mention whether the imbalance is due to load, utilization, nr_tasks or misfit_tasks. Remove this field from /proc/schedstat. Currently there is no field in /proc/schedstat to report different types of imbalances. Introduce new fields in /proc/schedstat to report the total imbalances in load, utilization, nr_tasks or misfit_tasks. Added fields to /proc/schedstat: - lb_imbalance_load: Total imbalance due to load. - lb_imbalance_util: Total imbalance due to utilization. - lb_imbalance_task: Total imbalance due to number of tasks. - lb_imbalance_misfit: Total imbalance due to misfit tasks. Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com> Link: https://lore.kernel.org/r/20241220063224.17767-4-swapnil.sapkal@amd.com
2024-12-20sched/fair: Cleanup in migrate_degrades_locality() to improve readabilityPeter Zijlstra
migrate_degrade_locality() would return {1, 0, -1} respectively to indicate that migration would degrade-locality, would improve locality, would be ambivalent to locality improvements. This patch improves readability by changing the return value to mean: * Any positive value degrades locality * 0 migration doesn't affect locality * Any negative value improves locality [Swapnil: Fixed comments around code and wrote commit log] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Not-yet-signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20241220063224.17767-3-swapnil.sapkal@amd.com
2024-12-20sched/fair: Fix value reported by hot tasks pulled in /proc/schedstatPeter Zijlstra
In /proc/schedstat, lb_hot_gained reports the number hot tasks pulled during load balance. This value is incremented in can_migrate_task() if the task is migratable and hot. After incrementing the value, load balancer can still decide not to migrate this task leading to wrong accounting. Fix this by incrementing stats when hot tasks are detached. This issue only exists in detach_tasks() where we can decide to not migrate hot task even if it is migratable. However, in detach_one_task(), we migrate it unconditionally. [Swapnil: Handled the case where nr_failed_migrations_hot was not accounted properly and wrote commit log] Fixes: d31980846f96 ("sched: Move up affinity check to mitigate useless redoing overhead") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reported-by: "Gautham R. Shenoy" <gautham.shenoy@amd.com> Not-yet-signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20241220063224.17767-2-swapnil.sapkal@amd.com
2024-12-20sched/fair: Update comments after sched_tick() rename.Sebastian Andrzej Siewior
scheduler_tick() was renamed to sched_tick() in 86dd6c04ef9f2 ("sched/balancing: Rename scheduler_tick() => sched_tick()"). Update comments still referring to scheduler_tick. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20241219085839.302378-1-bigeasy@linutronix.de
2024-12-18PM: EM: Move sched domains rebuild function from schedutil to EMRafael J. Wysocki
Function sugov_eas_rebuild_sd() defined in the schedutil cpufreq governor implements generic functionality that may be useful in other places. In particular, there is a plan to use it in the intel_pstate driver in the future. For this reason, move it from schedutil to the energy model code and rename it to em_rebuild_sched_domains(). This also helps to get rid of some #ifdeffery in schedutil which is a plus. No intentional functional impact. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Christian Loehle <christian.loehle@arm.com>
2024-12-18cpufreq: schedutil: Fix superfluous updates caused by need_freq_updateSultan Alsawaf (unemployed)
A redundant frequency update is only truly needed when there is a policy limits change with a driver that specifies CPUFREQ_NEED_UPDATE_LIMITS. In spite of that, drivers specifying CPUFREQ_NEED_UPDATE_LIMITS receive a frequency update _all the time_, not just for a policy limits change, because need_freq_update is never cleared. Furthermore, ignore_dl_rate_limit()'s usage of need_freq_update also leads to a redundant frequency update, regardless of whether or not the driver specifies CPUFREQ_NEED_UPDATE_LIMITS, when the next chosen frequency is the same as the current one. Fix the superfluous updates by only honoring CPUFREQ_NEED_UPDATE_LIMITS when there's a policy limits change, and clearing need_freq_update when a requisite redundant update occurs. This is neatly achieved by moving up the CPUFREQ_NEED_UPDATE_LIMITS test and instead setting need_freq_update to false in sugov_update_next_freq(). Fixes: 600f5badb78c ("cpufreq: schedutil: Don't skip freq update when limits change") Signed-off-by: Sultan Alsawaf (unemployed) <sultan@kerneltoast.com> Reviewed-by: Christian Loehle <christian.loehle@arm.com> Link: https://patch.msgid.link/20241212015734.41241-2-sultan@kerneltoast.com Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2024-12-17sched/fair: Fix CPU bandwidth limit bypass during CPU hotplugVishal Chourasia
CPU controller limits are not properly enforced during CPU hotplug operations, particularly during CPU offline. When a CPU goes offline, throttled processes are unintentionally being unthrottled across all CPUs in the system, allowing them to exceed their assigned quota limits. Consider below for an example, Assigning 6.25% bandwidth limit to a cgroup in a 8 CPU system, where, workload is running 8 threads for 20 seconds at 100% CPU utilization, expected (user+sys) time = 10 seconds. $ cat /sys/fs/cgroup/test/cpu.max 50000 100000 $ ./ebizzy -t 8 -S 20 // non-hotplug case real 20.00 s user 10.81 s // intended behaviour sys 0.00 s $ ./ebizzy -t 8 -S 20 // hotplug case real 20.00 s user 14.43 s // Workload is able to run for 14 secs sys 0.00 s // when it should have only run for 10 secs During CPU hotplug, scheduler domains are rebuilt and cpu_attach_domain is called for every active CPU to update the root domain. That ends up calling rq_offline_fair which un-throttles any throttled hierarchies. Unthrottling should only occur for the CPU being hotplugged to allow its throttled processes to become runnable and get migrated to other CPUs. With current patch applied, $ ./ebizzy -t 8 -S 20 // hotplug case real 21.00 s user 10.16 s // intended behaviour sys 0.00 s This also has another symptom, when a CPU goes offline, and if the cfs_rq is not in throttled state and the runtime_remaining still had plenty remaining, it gets reset to 1 here, causing the runtime_remaining of cfs_rq to be quickly depleted. Note: hotplug operation (online, offline) was performed in while(1) loop v3: https://lore.kernel.org/all/20241210102346.228663-2-vishalc@linux.ibm.com v2: https://lore.kernel.org/all/20241207052730.1746380-2-vishalc@linux.ibm.com v1: https://lore.kernel.org/all/20241126064812.809903-2-vishalc@linux.ibm.com Suggested-by: Zhang Qiao <zhangqiao22@huawei.com> Signed-off-by: Vishal Chourasia <vishalc@linux.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com> Tested-by: Samir Mulani <samir@linux.ibm.com> Link: https://lore.kernel.org/r/20241212043102.584863-2-vishalc@linux.ibm.com
2024-12-15Merge tag 'sched_urgent_for_v6.13_rc3-p2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fixes from Borislav Petkov: - Prevent incorrect dequeueing of the deadline dlserver helper task and fix its time accounting - Properly track the CFS runqueue runnable stats - Check the total number of all queued tasks in a sched fair's runqueue hierarchy before deciding to stop the tick - Fix the scheduling of the task that got woken last (NEXT_BUDDY) by preventing those from being delayed * tag 'sched_urgent_for_v6.13_rc3-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/dlserver: Fix dlserver time accounting sched/dlserver: Fix dlserver double enqueue sched/eevdf: More PELT vs DELAYED_DEQUEUE sched/fair: Fix sched_can_stop_tick() for fair tasks sched/fair: Fix NEXT_BUDDY
2024-12-13sched_ext: Use sizeof_field for key_len in dsq_hash_paramsLiang Jie
Update the `dsq_hash_params` initialization to use `sizeof_field` for the `key_len` field instead of a hardcoded value. This improves code readability and ensures the key length dynamically matches the size of the `id` field in the `scx_dispatch_q` structure. Signed-off-by: Liang Jie <liangjie@lixiang.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-13sched/dlserver: Fix dlserver time accountingVineeth Pillai (Google)
dlserver time is accounted when: - dlserver is active and the dlserver proxies the cfs task. - dlserver is active but deferred and cfs task runs after being picked through the normal fair class pick. dl_server_update is called in two places to make sure that both the above times are accounted for. But it doesn't check if dlserver is active or not. Now that we have this dl_server_active flag, we can consolidate dl_server_update into one place and all we need to check is whether dlserver is active or not. When dlserver is active there is only two possible conditions: - dlserver is deferred. - cfs task is running on behalf of dlserver. Fixes: a110a81c52a9 ("sched/deadline: Deferrable dl server") Signed-off-by: "Vineeth Pillai (Google)" <vineeth@bitbyteword.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk> # ROCK 5B Link: https://lore.kernel.org/r/20241213032244.877029-2-vineeth@bitbyteword.org
2024-12-13sched/dlserver: Fix dlserver double enqueueVineeth Pillai (Google)
dlserver can get dequeued during a dlserver pick_task due to the delayed deueue feature and this can lead to issues with dlserver logic as it still thinks that dlserver is on the runqueue. The dlserver throttling and replenish logic gets confused and can lead to double enqueue of dlserver. Double enqueue of dlserver could happend due to couple of reasons: Case 1 ------ Delayed dequeue feature[1] can cause dlserver being stopped during a pick initiated by dlserver: __pick_next_task pick_task_dl -> server_pick_task pick_task_fair pick_next_entity (if (sched_delayed)) dequeue_entities dl_server_stop server_pick_task goes ahead with update_curr_dl_se without knowing that dlserver is dequeued and this confuses the logic and may lead to unintended enqueue while the server is stopped. Case 2 ------ A race condition between a task dequeue on one cpu and same task's enqueue on this cpu by a remote cpu while the lock is released causing dlserver double enqueue. One cpu would be in the schedule() and releasing RQ-lock: current->state = TASK_INTERRUPTIBLE(); schedule(); deactivate_task() dl_stop_server(); pick_next_task() pick_next_task_fair() sched_balance_newidle() rq_unlock(this_rq) at which point another CPU can take our RQ-lock and do: try_to_wake_up() ttwu_queue() rq_lock() ... activate_task() dl_server_start() --> first enqueue wakeup_preempt() := check_preempt_wakeup_fair() update_curr() update_curr_task() if (current->dl_server) dl_server_update() enqueue_dl_entity() --> second enqueue This bug was not apparent as the enqueue in dl_server_start doesn't usually happen because of the defer logic. But as a side effect of the first case(dequeue during dlserver pick), dl_throttled and dl_yield will be set and this causes the time accounting of dlserver to messup and then leading to a enqueue in dl_server_start. Have an explicit flag representing the status of dlserver to avoid the confusion. This is set in dl_server_start and reset in dlserver_stop. Fixes: 63ba8422f876 ("sched/deadline: Introduce deadline servers") Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: "Vineeth Pillai (Google)" <vineeth@bitbyteword.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Marcel Ziswiler <marcel.ziswiler@codethink.co.uk> # ROCK 5B Link: https://lkml.kernel.org/r/20241213032244.877029-1-vineeth@bitbyteword.org
2024-12-11sched_ext: Fix invalid irq restore in scx_ops_bypass()Tejun Heo
While adding outer irqsave/restore locking, 0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()") forgot to convert an inner rq_unlock_irqrestore() to rq_unlock() which could re-enable IRQ prematurely leading to the following warning: raw_local_irq_restore() called with IRQs enabled WARNING: CPU: 1 PID: 96 at kernel/locking/irqflag-debug.c:10 warn_bogus_irq_restore+0x30/0x40 ... Sched_ext: create_dsq (enabling) pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : warn_bogus_irq_restore+0x30/0x40 lr : warn_bogus_irq_restore+0x30/0x40 ... Call trace: warn_bogus_irq_restore+0x30/0x40 (P) warn_bogus_irq_restore+0x30/0x40 (L) scx_ops_bypass+0x224/0x3b8 scx_ops_enable.isra.0+0x2c8/0xaa8 bpf_scx_reg+0x18/0x30 ... irq event stamp: 33739 hardirqs last enabled at (33739): [<ffff8000800b699c>] scx_ops_bypass+0x174/0x3b8 hardirqs last disabled at (33738): [<ffff800080d48ad4>] _raw_spin_lock_irqsave+0xb4/0xd8 Drop the stray _irqrestore(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Ihor Solodrai <ihor.solodrai@pm.me> Link: http://lkml.kernel.org/r/qC39k3UsonrBYD_SmuxHnZIQLsuuccoCrkiqb_BT7DvH945A1_LZwE4g-5Pu9FcCtqZt4lY1HhIPi0homRuNWxkgo1rgP3bkxa0donw8kV4=@pm.me Fixes: 0e7ffff1b811 ("scx: Fix raciness in scx_ops_bypass()") Cc: stable@vger.kernel.org # v6.12
2024-12-10sched: deadline: Cleanup goto label in pick_earliest_pushable_dl_taskJohn Stultz
Commit 8b5e770ed7c0 ("sched/deadline: Optimize pull_dl_task()") added a goto label seems would be better written as a while loop. So replace the goto with a while loop, to make it easier to read. Reported-by: Todd Kjos <tkjos@google.com> Signed-off-by: John Stultz <jstultz@google.com> Reviewed-and-tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Juri Lelli <juri.lelli@redhat.com> Link: https://lore.kernel.org/r/20241206000009.1226085-1-jstultz@google.com
2024-12-09Merge tag 'sched_urgent_for_v6.13_rc3' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fixes from Borislav Petkov: - Remove wrong enqueueing of a task for a later wakeup when a task blocks on a RT mutex - Do not setup a new deadline entity on a boosted task as that has happened already - Update preempt= kernel command line param - Prevent needless softirqd wakeups in the idle task's context - Detect the case where the idle load balancer CPU becomes busy and avoid unnecessary load balancing invocation - Remove an unnecessary load balancing need_resched() call in nohz_csd_func() - Allow for raising of SCHED_SOFTIRQ softirq type on RT but retain the warning to catch any other cases - Remove a wrong warning when a cpuset update makes the task affinity no longer a subset of the cpuset * tag 'sched_urgent_for_v6.13_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking: rtmutex: Fix wake_q logic in task_blocks_on_rt_mutex sched/deadline: Fix warning in migrate_enable for boosted tasks sched/core: Update kernel boot parameters for LAZY preempt. sched/core: Prevent wakeup of ksoftirqd during idle load balance sched/fair: Check idle_cpu() before need_resched() to detect ilb CPU turning busy sched/core: Remove the unnecessary need_resched() check in nohz_csd_func() softirq: Allow raising SCHED_SOFTIRQ from SMP-call-function on RT kernel sched: fix warning in sched_setaffinity sched/deadline: Fix replenish_dl_new_period dl_server condition
2024-12-09sched/fair: Untangle NEXT_BUDDY and pick_next_task()Peter Zijlstra
There are 3 sites using set_next_buddy() and only one is conditional on NEXT_BUDDY, the other two sites are unconditional; to note: - yield_to_task() - cgroup dequeue / pick optimization However, having NEXT_BUDDY control both the wakeup-preemption and the picking side of things means its near useless. Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20241129101541.GA33464@noisy.programming.kicks-ass.net
2024-12-09sched/fair: Mark m*_vruntime() with __maybe_unusedAndy Shevchenko
When max_vruntime() is unused, it prevents kernel builds with clang, `make W=1` and CONFIG_WERROR=y: kernel/sched/fair.c:526:19: error: unused function 'max_vruntime' [-Werror,-Wunused-function] 526 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) | ^~~~~~~~~~~~ Fix this by marking them with __maybe_unused (all cases for the sake of symmetry). See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static inline functions for W=1 build"). Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20241202173546.634433-1-andriy.shevchenko@linux.intel.com
2024-12-09sched/fair: Fix variable declaration positionVincent Guittot
Move variable declaration at the beginning of the function Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-12-vincent.guittot@linaro.org
2024-12-09sched/fair: Do not try to migrate delayed dequeue taskVincent Guittot
Migrating a delayed dequeued task doesn't help in balancing the number of runnable tasks in the system. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-11-vincent.guittot@linaro.org
2024-12-09sched/fair: Rename cfs_rq.nr_running into nr_queuedVincent Guittot
Rename cfs_rq.nr_running into cfs_rq.nr_queued which better reflects the reality as the value includes both the ready to run tasks and the delayed dequeue tasks. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-10-vincent.guittot@linaro.org
2024-12-09sched/fair: Remove unused cfs_rq.idle_nr_runningVincent Guittot
cfs_rq.idle_nr_running field is not used anywhere so we can remove the useless associated computation. Last user went in commit 5e963f2bd465 ("sched/fair: Commit to EEVDF"). Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-9-vincent.guittot@linaro.org
2024-12-09sched/fair: Rename cfs_rq.idle_h_nr_running into h_nr_idleVincent Guittot
Use same naming convention as others starting with h_nr_* and rename idle_h_nr_running into h_nr_idle. The "running" is not correct anymore as it includes delayed dequeue tasks as well. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-8-vincent.guittot@linaro.org
2024-12-09sched/fair: Removed unsued cfs_rq.h_nr_delayedVincent Guittot
h_nr_delayed is not used anymore. We now have: - h_nr_runnable which tracks tasks ready to run - h_nr_queued which tracks enqueued tasks either ready to run or delayed dequeue Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-7-vincent.guittot@linaro.org
2024-12-09sched/fair: Use the new cfs_rq.h_nr_runnableVincent Guittot
Use the new h_nr_runnable that tracks only queued and runnable tasks in the statistics that are used to balance the system: - PELT runnable_avg - deciding if a group is overloaded or has spare capacity - numa stats - reduced capacity management - load balance - nohz kick It should be noticed that the rq->nr_running still counts the delayed dequeued tasks as delayed dequeue is a fair feature that is meaningless at core level. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-6-vincent.guittot@linaro.org
2024-12-09sched/fair: Add new cfs_rq.h_nr_runnableVincent Guittot
With delayed dequeued feature, a sleeping sched_entity remains queued in the rq until its lag has elapsed. As a result, it stays also visible in the statistics that are used to balance the system and in particular the field cfs.h_nr_queued when the sched_entity is associated to a task. Create a new h_nr_runnable that tracks only queued and runnable tasks. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-5-vincent.guittot@linaro.org
2024-12-09sched/fair: Rename h_nr_running into h_nr_queuedVincent Guittot
With delayed dequeued feature, a sleeping sched_entity remains queued in the rq until its lag has elapsed but can't run. Rename h_nr_running into h_nr_queued to reflect this new behavior. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-4-vincent.guittot@linaro.org
2024-12-09Merge branch 'sched/urgent'Peter Zijlstra
Sync with urgent bits as a base for further work. Signed-off-by: Peter Zijlstra <peterz@infradead.org>
2024-12-09sched/eevdf: More PELT vs DELAYED_DEQUEUEPeter Zijlstra
Vincent and Dietmar noted that while commit fc1892becd56 ("sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE") fixes the entity runnable stats, it does not adjust the cfs_rq runnable stats, which are based off of h_nr_running. Track h_nr_delayed such that we can discount those and adjust the signal. Fixes: fc1892becd56 ("sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE") Closes: https://lore.kernel.org/lkml/a9a45193-d0c6-4ba2-a822-464ad30b550e@arm.com/ Closes: https://lore.kernel.org/lkml/CAKfTPtCNUvWE_GX5LyvTF-WdxUT=ZgvZZv-4t=eWntg5uOFqiQ@mail.gmail.com/ [ Fixes checkpatch warnings and rebased ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Reported-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Link: https://lore.kernel.org/r/20241202174606.4074512-3-vincent.guittot@linaro.org
2024-12-09sched/fair: Fix sched_can_stop_tick() for fair tasksVincent Guittot
We can't stop the tick of a rq if there are at least 2 tasks enqueued in the whole hierarchy and not only at the root cfs rq. rq->cfs.nr_running tracks the number of sched_entity at one level whereas rq->cfs.h_nr_running tracks all queued tasks in the hierarchy. Fixes: 11cc374f4643b ("sched_ext: Simplify scx_can_stop_tick() invocation in sched_can_stop_tick()") Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20241202174606.4074512-2-vincent.guittot@linaro.org
2024-12-09sched/fair: Fix NEXT_BUDDYK Prateek Nayak
Adam reports that enabling NEXT_BUDDY insta triggers a WARN in pick_next_entity(). Moving clear_buddies() up before the delayed dequeue bits ensures no ->next buddy becomes delayed. Further ensure no new ->next buddy ever starts as delayed. Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue") Reported-by: Adam Li <adamli@os.amperecomputing.com> Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Adam Li <adamli@os.amperecomputing.com> Link: https://lkml.kernel.org/r/670a0d54-e398-4b1f-8a6e-90784e2fdf89@amd.com
2024-12-05sched/numa: fix memory leak due to the overwritten vma->numab_stateAdrian Huang
[Problem Description] When running the hackbench program of LTP, the following memory leak is reported by kmemleak. # /opt/ltp/testcases/bin/hackbench 20 thread 1000 Running with 20*40 (== 800) tasks. # dmesg | grep kmemleak ... kmemleak: 480 new suspected memory leaks (see /sys/kernel/debug/kmemleak) kmemleak: 665 new suspected memory leaks (see /sys/kernel/debug/kmemleak) # cat /sys/kernel/debug/kmemleak unreferenced object 0xffff888cd8ca2c40 (size 64): comm "hackbench", pid 17142, jiffies 4299780315 hex dump (first 32 bytes): ac 74 49 00 01 00 00 00 4c 84 49 00 01 00 00 00 .tI.....L.I..... 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc bff18fd4): [<ffffffff81419a89>] __kmalloc_cache_noprof+0x2f9/0x3f0 [<ffffffff8113f715>] task_numa_work+0x725/0xa00 [<ffffffff8110f878>] task_work_run+0x58/0x90 [<ffffffff81ddd9f8>] syscall_exit_to_user_mode+0x1c8/0x1e0 [<ffffffff81dd78d5>] do_syscall_64+0x85/0x150 [<ffffffff81e0012b>] entry_SYSCALL_64_after_hwframe+0x76/0x7e ... This issue can be consistently reproduced on three different servers: * a 448-core server * a 256-core server * a 192-core server [Root Cause] Since multiple threads are created by the hackbench program (along with the command argument 'thread'), a shared vma might be accessed by two or more cores simultaneously. When two or more cores observe that vma->numab_state is NULL at the same time, vma->numab_state will be overwritten. Although current code ensures that only one thread scans the VMAs in a single 'numa_scan_period', there might be a chance for another thread to enter in the next 'numa_scan_period' while we have not gotten till numab_state allocation [1]. Note that the command `/opt/ltp/testcases/bin/hackbench 50 process 1000` cannot the reproduce the issue. It is verified with 200+ test runs. [Solution] Use the cmpxchg atomic operation to ensure that only one thread executes the vma->numab_state assignment. [1] https://lore.kernel.org/lkml/1794be3c-358c-4cdc-a43d-a1f841d91ef7@amd.com/ Link: https://lkml.kernel.org/r/20241113102146.2384-1-ahuang12@lenovo.com Fixes: ef6a22b70f6d ("sched/numa: apply the scan delay to every new vma") Signed-off-by: Adrian Huang <ahuang12@lenovo.com> Reported-by: Jiwei Sun <sunjw10@lenovo.com> Reviewed-by: Raghavendra K T <raghavendra.kt@amd.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Ben Segall <bsegall@google.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Valentin Schneider <vschneid@redhat.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-12-04sched_ext: Use the NUMA scheduling domain for NUMA optimizationsAndrea Righi
Rely on the NUMA scheduling domain topology, instead of accessing NUMA topology information directly. There is basically no functional change, but in this way we ensure consistent use of the same topology information determined by the scheduling subsystem. Fixes: f6ce6b949304 ("sched_ext: Do not enable LLC/NUMA optimizations when domains overlap") Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2024-12-02sched: Unify HK_TYPE_{TIMER|TICK|MISC} to HK_TYPE_KERNEL_NOISEWaiman Long
As all the non-domain and non-managed_irq housekeeping types have been unified to HK_TYPE_KERNEL_NOISE, replace all these references in the scheduler to use HK_TYPE_KERNEL_NOISE. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20241030175253.125248-5-longman@redhat.com
2024-12-02sched/isolation: Consolidate housekeeping cpumasks that are always identicalWaiman Long
The housekeeping cpumasks are only set by two boot commandline parameters: "nohz_full" and "isolcpus". When there is more than one of "nohz_full" or "isolcpus", the extra ones must have the same CPU list or the setup will fail partially. The HK_TYPE_DOMAIN and HK_TYPE_MANAGED_IRQ types are settable by "isolcpus" only and their settings can be independent of the other types. The other housekeeping types are all set by "nohz_full" or "isolcpus=nohz" without a way to set them individually. So they all have identical cpumasks. There is actually no point in having different cpumasks for these "nohz_full" only housekeeping types. Consolidate these types to use the same cpumask by aliasing them to the same value. If there is a need to set any of them independently in the future, we can break them out to their own cpumasks again. With this change, the number of cpumasks in the housekeeping structure drops from 9 to 3. Other than that, there should be no other functional change. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20241030175253.125248-4-longman@redhat.com
2024-12-02sched/isolation: Make "isolcpus=nohz" equivalent to "nohz_full"Waiman Long
The "isolcpus=nohz" boot parameter and flag were used to disable tick when running a single task. Nowsdays, this "nohz" flag is seldomly used as it is included as part of the "nohz_full" parameter. Extend this flag to cover other kernel noises disabled by the "nohz_full" parameter to make them equivalent. This also eliminates the need to use both the "isolcpus" and the "nohz_full" parameters to fully isolated a given set of CPUs. Suggested-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20241030175253.125248-3-longman@redhat.com
2024-12-02sched/core: Remove HK_TYPE_SCHEDWaiman Long
The HK_TYPE_SCHED housekeeping type is defined but not set anywhere. So any code that try to use HK_TYPE_SCHED are essentially dead code. So remove HK_TYPE_SCHED and any code that use it. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20241030175253.125248-2-longman@redhat.com
2024-12-02sched/fair: Remove CONFIG_CFS_BANDWIDTH=n definition of cfs_bandwidth_used()Valentin Schneider
Andy reported that clang gets upset with CONFIG_CFS_BANDWIDTH=n: kernel/sched/fair.c:6580:20: error: unused function 'cfs_bandwidth_used' [-Werror,-Wunused-function] 6580 | static inline bool cfs_bandwidth_used(void) | ^~~~~~~~~~~~~~~~~~ Indeed, cfs_bandwidth_used() is only used within functions defined under CONFIG_CFS_BANDWIDTH=y. Remove its CONFIG_CFS_BANDWIDTH=n declaration & definition. Reported-by: Andy Shevchenko <andy.shevchenko@gmail.com> Signed-off-by: Valentin Schneider <vschneid@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Link: https://lore.kernel.org/r/20241127165501.160004-1-vschneid@redhat.com
2024-12-02sched/deadline: Consolidate Timer CancellationWander Lairson Costa
After commit b58652db66c9 ("sched/deadline: Fix task_struct reference leak"), I identified additional calls to hrtimer_try_to_cancel that might also require a dl_server check. It remains unclear whether this omission was intentional or accidental in those contexts. This patch consolidates the timer cancellation logic into dedicated functions, ensuring consistent behavior across all calls. Additionally, it reduces code duplication and improves overall code cleanliness. Note the use of the __always_inline keyword. In some instances, we have a task_struct pointer, dereference the dl member, and then use the container_of macro to retrieve the task_struct pointer again. By inlining the code, the compiler can potentially optimize out this redundant round trip. Signed-off-by: Wander Lairson Costa <wander@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Juri Lelli <juri.lelli@redhat.com> Link: https://lore.kernel.org/r/20240724142253.27145-3-wander@redhat.com
2024-12-02sched/deadline: Check bandwidth overflow earlier for hotplugJuri Lelli
Currently we check for bandwidth overflow potentially due to hotplug operations at the end of sched_cpu_deactivate(), after the cpu going offline has already been removed from scheduling, active_mask, etc. This can create issues for DEADLINE tasks, as there is a substantial race window between the start of sched_cpu_deactivate() and the moment we possibly decide to roll-back the operation if dl_bw_deactivate() returns failure in cpuset_cpu_inactive(). An example is a throttled task that sees its replenishment timer firing while the cpu it was previously running on is considered offline, but before dl_bw_deactivate() had a chance to say no and roll-back happened. Fix this by directly calling dl_bw_deactivate() first thing in sched_cpu_deactivate() and do the required calculation in the former function considering the cpu passed as an argument as offline already. By doing so we also simplify sched_cpu_deactivate(), as there is no need anymore for any kind of roll-back if we fail early. Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Phil Auld <pauld@redhat.com> Tested-by: Waiman Long <longman@redhat.com> Link: https://lore.kernel.org/r/Zzc1DfPhbvqDDIJR@jlelli-thinkpadt14gen4.remote.csb
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