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* sched/fair: Fix typo describing flags in enqueue_entityKamalesh Babulal2013-06-27
| | | | | | | | | | Fix spelling of 'calling' in description of se flags in enqueue_entity(). Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Cc: peterz@infradead.org Link: http://lkml.kernel.org/r/20130627055418.GA18582@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/cfs_rq: Change atomic64_t removed_load to atomic_long_tAlex Shi2013-06-27
| | | | | | | | | | | | | | Similar to runnable_load_avg, blocked_load_avg variable, long type is enough for removed_load in 64 bit or 32 bit machine. Then we avoid the expensive atomic64 operations on 32 bit machine. Signed-off-by: Alex Shi <alex.shi@intel.com> Reviewed-by: Paul Turner <pjt@google.com> Tested-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-12-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/tg: Use 'unsigned long' for load variable in task groupAlex Shi2013-06-27
| | | | | | | | | | | | | | | Since tg->load_avg is smaller than tg->load_weight, we don't need a atomic64_t variable for load_avg in 32 bit machine. The same reason for cfs_rq->tg_load_contrib. The atomic_long_t/unsigned long variable type are more efficient and convenience for them. Signed-off-by: Alex Shi <alex.shi@intel.com> Tested-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-11-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Change cfs_rq load avg to unsigned longAlex Shi2013-06-27
| | | | | | | | | | | | | Since the 'u64 runnable_load_avg, blocked_load_avg' in cfs_rq struct are smaller than 'unsigned long' cfs_rq->load.weight. We don't need u64 vaiables to describe them. unsigned long is more efficient and convenience. Signed-off-by: Alex Shi <alex.shi@intel.com> Reviewed-by: Paul Turner <pjt@google.com> Tested-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-10-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Consider runnable load average in move_tasks()Alex Shi2013-06-27
| | | | | | | | | | | | | | | Aside from using runnable load average in background, move_tasks is also the key function in load balance. We need consider the runnable load average in it in order to make it an apple to apple load comparison. Morten had caught a div u64 bug on ARM, thanks! Thanks-to: Morten Rasmussen <morten.rasmussen@arm.com> Signed-off-by: Alex Shi <alex.shi@intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-8-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Compute runnable load avg in cpu_load and cpu_avg_load_per_taskAlex Shi2013-06-27
| | | | | | | | | | | | | | | | | | They are the base values in load balance, update them with rq runnable load average, then the load balance will consider runnable load avg naturally. We also try to include the blocked_load_avg as cpu load in balancing, but that cause kbuild performance drop 6% on every Intel machine, and aim7/oltp drop on some of 4 CPU sockets machines. Or only add blocked_load_avg into get_rq_runable_load, hackbench still drop a little on NHM EX. Signed-off-by: Alex Shi <alex.shi@intel.com> Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-7-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Fix sleep time double accounting in enqueue entityAlex Shi2013-06-27
| | | | | | | | | | | | | | | | | | | | | | The woken migrated task will __synchronize_entity_decay(se); in migrate_task_rq_fair, then it needs to set `se->avg.last_runnable_update -= (-se->avg.decay_count) << 20' before update_entity_load_avg, in order to avoid sleep time is updated twice for se.avg.load_avg_contrib in both __syncchronize and update_entity_load_avg. However if the sleeping task is woken up from the same cpu, it miss the last_runnable_update before update_entity_load_avg(se, 0, 1), then the sleep time was used twice in both functions. So we need to remove the double sleep time accounting. Paul also contributed some code comments in this commit. Signed-off-by: Alex Shi <alex.shi@intel.com> Reviewed-by: Paul Turner <pjt@google.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-5-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Set an initial value of runnable avg for new forked taskAlex Shi2013-06-27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We need to initialize the se.avg.{decay_count, load_avg_contrib} for a new forked task. Otherwise random values of above variables cause a mess when a new task is enqueued: enqueue_task_fair enqueue_entity enqueue_entity_load_avg and make fork balancing imbalance due to incorrect load_avg_contrib. Further more, Morten Rasmussen notice some tasks were not launched at once after created. So Paul and Peter suggest giving a start value for new task runnable avg time same as sched_slice(). PeterZ said: > So the 'problem' is that our running avg is a 'floating' average; ie. it > decays with time. Now we have to guess about the future of our newly > spawned task -- something that is nigh impossible seeing these CPU > vendors keep refusing to implement the crystal ball instruction. > > So there's two asymptotic cases we want to deal well with; 1) the case > where the newly spawned program will be 'nearly' idle for its lifetime; > and 2) the case where its cpu-bound. > > Since we have to guess, we'll go for worst case and assume its > cpu-bound; now we don't want to make the avg so heavy adjusting to the > near-idle case takes forever. We want to be able to quickly adjust and > lower our running avg. > > Now we also don't want to make our avg too light, such that it gets > decremented just for the new task not having had a chance to run yet -- > even if when it would run, it would be more cpu-bound than not. > > So what we do is we make the initial avg of the same duration as that we > guess it takes to run each task on the system at least once -- aka > sched_slice(). > > Of course we can defeat this with wakeup/fork bombs, but in the 'normal' > case it should be good enough. Paul also contributed most of the code comments in this commit. Signed-off-by: Alex Shi <alex.shi@intel.com> Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com> Reviewed-by: Paul Turner <pjt@google.com> [peterz; added explanation of sched_slice() usage] Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1371694737-29336-4-git-send-email-alex.shi@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Revert "sched: Introduce temporary FAIR_GROUP_SCHED dependency for ↵Alex Shi2013-06-27
| | | | | | | | | | | | | | | load-tracking" Remove CONFIG_FAIR_GROUP_SCHED that covers the runnable info, then we can use runnable load variables. Also remove 2 CONFIG_FAIR_GROUP_SCHED setting which is not in reverted patch(introduced in 9ee474f), but also need to revert. Signed-off-by: Alex Shi <alex.shi@intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/51CA76A3.3050207@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Femove the useless declaration in kernel/sched/fair.cMichael Wang2013-06-19
| | | | | | | | | | default_cfs_period(), do_sched_cfs_period_timer(), do_sched_cfs_slack_timer() already defined previously, no need to declare again. Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/51AD8808.7020608@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Refine the code in unthrottle_cfs_rq()Michael Wang2013-06-19
| | | | | | | | | Directly use rq to save some code. Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/51AD87EB.1070605@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/fair: Remove unused variable from expire_cfs_rq_runtime()Kamalesh Babulal2013-05-31
| | | | | | | | | | | | | | | | Commit 78becc2709 ("sched: Use an accessor to read the rq clock") introduces rq_clock(), which obsoletes the use of the "rq" variable in expire_cfs_rq_runtime() and triggers this build warning: kernel/sched/fair.c: In function 'expire_cfs_rq_runtime': kernel/sched/fair.c:2159:13: warning: unused variable 'rq' [-Wunused-variable] Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Paul Turner <pjt@google.com> Cc: peterz@infradead.org Link: http://lkml.kernel.org/r/1369904660-14169-1-git-send-email-kamalesh@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Use an accessor to read the rq clockFrederic Weisbecker2013-05-28
| | | | | | | | | | | | | | | | Read the runqueue clock through an accessor. This prepares for adding a debugging infrastructure to detect missing or redundant calls to update_rq_clock() between a scheduler's entry and exit point. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Turner <pjt@google.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1365724262-20142-6-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Update rq clock earlier in unthrottle_cfs_rqFrederic Weisbecker2013-05-28
| | | | | | | | | | | | | | | In this function we are making use of rq->clock right before the update of the rq clock, let's just call update_rq_clock() just before that to avoid using a stale rq clock value. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Turner <pjt@google.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1365724262-20142-5-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Update rq clock before setting fair group sharesFrederic Weisbecker2013-05-28
| | | | | | | | | | | | | | | | | | Because we may update the execution time in sched_group_set_shares()->update_cfs_shares()->reweight_entity()->update_curr() before reweighting the entity while setting the group shares and this requires an uptodate version of the runqueue clock. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Turner <pjt@google.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1365724262-20142-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched/cleanups' into sched/coreIngo Molnar2013-05-28
|\ | | | | | | | | | | Merge reason: these bits, formerly in sched/urgent, are too late for v3.10. Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Move update_load_*() methods from sched.h to fair.cPaul Gortmaker2013-05-07
| | | | | | | | | | | | | | | | | | | | | | These inlines are only used by kernel/sched/fair.c so they do not need to be present in the main kernel/sched/sched.h file. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: http://lkml.kernel.org/r/1366398650-31599-3-git-send-email-paul.gortmaker@windriver.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Use this_rq() helperNathan Zimmer2013-05-10
|/ | | | | | | | | | | | | | | | It is a few instructions more efficent to and slightly more readable to use this_rq()-> instead of cpu_rq(smp_processor_id())-> . Size comparison of kernel/sched/fair.o: text data bss dec hex filename 27972 122 26 28120 6dd8 fair.o.before 27956 122 26 28104 6dc8 fair.o.after Signed-off-by: Nathan Zimmer <nzimmer@sgi.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1368116643-87971-1-git-send-email-nzimmer@sgi.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge commit '8700c95adb03' into timers/nohzFrederic Weisbecker2013-05-02
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | The full dynticks tree needs the latest RCU and sched upstream updates in order to fix some dependencies. Merge a common upstream merge point that has these updates. Conflicts: include/linux/perf_event.h kernel/rcutree.h kernel/rcutree_plugin.h Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
| * sched: Fix init NOHZ_IDLE flagVincent Guittot2013-04-26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On my SMP platform which is made of 5 cores in 2 clusters, I have the nr_busy_cpu field of sched_group_power struct that is not null when the platform is fully idle - which makes the scheduler unhappy. The root cause is: During the boot sequence, some CPUs reach the idle loop and set their NOHZ_IDLE flag while waiting for others CPUs to boot. But the nr_busy_cpus field is initialized later with the assumption that all CPUs are in the busy state whereas some CPUs have already set their NOHZ_IDLE flag. More generally, the NOHZ_IDLE flag must be initialized when new sched_domains are created in order to ensure that NOHZ_IDLE and nr_busy_cpus are aligned. This condition can be ensured by adding a synchronize_rcu() between the destruction of old sched_domains and the creation of new ones so the NOHZ_IDLE flag will not be updated with old sched_domain once it has been initialized. But this solution introduces a additionnal latency in the rebuild sequence that is called during cpu hotplug. As suggested by Frederic Weisbecker, another solution is to have the same rcu lifecycle for both NOHZ_IDLE and sched_domain struct. A new nohz_idle field is added to sched_domain so both status and sched_domain will share the same RCU lifecycle and will be always synchronized. In addition, there is no more need to protect nohz_idle against concurrent access as it is only modified by 2 exclusive functions called by local cpu. This solution has been prefered to the creation of a new struct with an extra pointer indirection for sched_domain. The synchronization is done at the cost of : - An additional indirection and a rcu_dereference for accessing nohz_idle. - We use only the nohz_idle field of the top sched_domain. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: linaro-kernel@lists.linaro.org Cc: peterz@infradead.org Cc: fweisbec@gmail.com Cc: pjt@google.com Cc: rostedt@goodmis.org Cc: efault@gmx.de Link: http://lkml.kernel.org/r/1366729142-14662-1-git-send-email-vincent.guittot@linaro.org [ Fixed !NO_HZ build bug. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Prevent to re-select dst-cpu in load_balance()Joonsoo Kim2013-04-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 88b8dac0 makes load_balance() consider other cpus in its group. But, in that, there is no code for preventing to re-select dst-cpu. So, same dst-cpu can be selected over and over. This patch add functionality to load_balance() in order to exclude cpu which is selected once. We prevent to re-select dst_cpu via env's cpus, so now, env's cpus is a candidate not only for src_cpus, but also dst_cpus. With this patch, we can remove lb_iterations and max_lb_iterations, because we decide whether we can go ahead or not via env's cpus. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Jason Low <jason.low2@hp.com> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366705662-3587-7-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Rename load_balance_tmpmask to load_balance_maskJoonsoo Kim2013-04-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | This name doesn't represent specific meaning. So rename it to imply it's purpose. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Jason Low <jason.low2@hp.com> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366705662-3587-6-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Move up affinity check to mitigate useless redoing overheadJoonsoo Kim2013-04-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, LBF_ALL_PINNED is cleared after affinity check is passed. So, if task migration is skipped by small load value or small imbalance value in move_tasks(), we don't clear LBF_ALL_PINNED. At last, we trigger 'redo' in load_balance(). Imbalance value is often so small that any tasks cannot be moved to other cpus and, of course, this situation may be continued after we change the target cpu. So this patch move up affinity check code and clear LBF_ALL_PINNED before evaluating load value in order to mitigate useless redoing overhead. In addition, re-order some comments correctly. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Jason Low <jason.low2@hp.com> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366705662-3587-5-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Don't consider other cpus in our group in case of NEWLY_IDLEJoonsoo Kim2013-04-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 88b8dac0 makes load_balance() consider other cpus in its group, regardless of idle type. When we do NEWLY_IDLE balancing, we should not consider it, because a motivation of NEWLY_IDLE balancing is to turn this cpu to non idle state if needed. This is not the case of other cpus. So, change code not to consider other cpus for NEWLY_IDLE balancing. With this patch, assign 'if (pulled_task) this_rq->idle_stamp = 0' in idle_balance() is corrected, because NEWLY_IDLE balancing doesn't consider other cpus. Assigning to 'this_rq->idle_stamp' is now valid. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Tested-by: Jason Low <jason.low2@hp.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366705662-3587-4-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Explicitly cpu_idle_type checking in rebalance_domains()Joonsoo Kim2013-04-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After commit 88b8dac0, dst-cpu can be changed in load_balance(), then we can't know cpu_idle_type of dst-cpu when load_balance() return positive. So, add explicit cpu_idle_type checking. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Tested-by: Jason Low <jason.low2@hp.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366705662-3587-3-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Change position of resched_cpu() in load_balance()Joonsoo Kim2013-04-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cur_ld_moved is reset if env.flags hit LBF_NEED_BREAK. So, there is possibility that we miss doing resched_cpu(). Correct it as changing position of resched_cpu() before checking LBF_NEED_BREAK. Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Tested-by: Jason Low <jason.low2@hp.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1366705662-3587-2-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Fix wrong rq's runnable_avg update with rt tasksVincent Guittot2013-04-21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current update of the rq's load can be erroneous when RT tasks are involved. The update of the load of a rq that becomes idle, is done only if the avg_idle is less than sysctl_sched_migration_cost. If RT tasks and short idle duration alternate, the runnable_avg will not be updated correctly and the time will be accounted as idle time when a CFS task wakes up. A new idle_enter function is called when the next task is the idle function so the elapsed time will be accounted as run time in the load of the rq, whatever the average idle time is. The function update_rq_runnable_avg is removed from idle_balance. When a RT task is scheduled on an idle CPU, the update of the rq's load is not done when the rq exit idle state because CFS's functions are not called. Then, the idle_balance, which is called just before entering the idle function, updates the rq's load and makes the assumption that the elapsed time since the last update, was only running time. As a consequence, the rq's load of a CPU that only runs a periodic RT task, is close to LOAD_AVG_MAX whatever the running duration of the RT task is. A new idle_exit function is called when the prev task is the idle function so the elapsed time will be accounted as idle time in the rq's load. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: linaro-kernel@lists.linaro.org Cc: peterz@infradead.org Cc: pjt@google.com Cc: fweisbec@gmail.com Cc: efault@gmx.de Link: http://lkml.kernel.org/r/1366302867-5055-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Fix comment in rebalance_domains()Libin2013-04-10
| | | | | | | | | | | | | | | | | | | | | | A comment in function rebalance_domains() mentions arch_init_sched_domains(), but that function does not exist anymore. The proper function is init_sched_domains(). Signed-off-by: Libin <huawei.libin@huawei.com> Cc: <peterz@infradead.org> Link: http://lkml.kernel.org/r/1364814841-49156-1-git-send-email-huawei.libin@huawei.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Simplify can_migrate_task()Zhang Hang2013-04-10
| | | | | | | | | | | | | | | | | | | | At this point tsk_cache_hot is always true, so no need to check it. Signed-off-by: Zhang Hang <bob.zhanghang@huawei.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/51650107.9040606@huawei.com [ Also remove unnecessary schedstat #ifdefs. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | nohz: Rename CONFIG_NO_HZ to CONFIG_NO_HZ_COMMONFrederic Weisbecker2013-04-03
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We are planning to convert the dynticks Kconfig options layout into a choice menu. The user must be able to easily pick any of the following implementations: constant periodic tick, idle dynticks, full dynticks. As this implies a mutual exclusion, the two dynticks implementions need to converge on the selection of a common Kconfig option in order to ease the sharing of a common infrastructure. It would thus seem pretty natural to reuse CONFIG_NO_HZ to that end. It already implements all the idle dynticks code and the full dynticks depends on all that code for now. So ideally the choice menu would propose CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED then both would select CONFIG_NO_HZ. On the other hand we want to stay backward compatible: if CONFIG_NO_HZ is set in an older config file, we want to enable CONFIG_NO_HZ_IDLE by default. But we can't afford both at the same time or we run into a circular dependency: 1) CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED both select CONFIG_NO_HZ 2) If CONFIG_NO_HZ is set, we default to CONFIG_NO_HZ_IDLE We might be able to support that from Kconfig/Kbuild but it may not be wise to introduce such a confusing behaviour. So to solve this, create a new CONFIG_NO_HZ_COMMON option which gathers the common code between idle and full dynticks (that common code for now is simply the idle dynticks code) and select it from their referring Kconfig. Then we'll later create CONFIG_NO_HZ_IDLE and map CONFIG_NO_HZ to it for backward compatibility. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
* sched: Fix variable name misnomer, add commentsAndrei Epure2013-03-14
| | | | | | | | | | The min_vruntime variable actually stores the maximum value. The added comment was taken from place_entity function. Signed-off-by: Andrei Epure <epure.andrei@gmail.com> Cc: peterz@infradead.org Link: http://lkml.kernel.org/r/1363115544-1964-1-git-send-email-epure.andrei@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Spelling fixAndrei Epure2013-03-11
| | | | | | | | Signed-off-by: Andrei Epure <epure.andrei@gmail.com> Cc: trivial@kernel.org Cc: peterz@infradead.org Link: http://lkml.kernel.org/r/1362996200-2674-1-git-send-email-epure.andrei@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Make default_scale_freq_power() staticLi Zefan2013-03-06
| | | | | | | | | | | As default_scale_{freq,smt}_power() and update_rt_power() are used in kernel/sched/fair.c only, annotate them as static functions. Signed-off-by: Li Zefan <lizefan@huawei.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/5135A7AF.8010900@huawei.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2013-02-19
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes from Ingo Molnar: "Main changes: - scheduler side full-dynticks (user-space execution is undisturbed and receives no timer IRQs) preparation changes that convert the cputime accounting code to be full-dynticks ready, from Frederic Weisbecker. - Initial sched.h split-up changes, by Clark Williams - select_idle_sibling() performance improvement by Mike Galbraith: " 1 tbench pair (worst case) in a 10 core + SMT package: pre 15.22 MB/sec 1 procs post 252.01 MB/sec 1 procs " - sched_rr_get_interval() ABI fix/change. We think this detail is not used by apps (so it's not an ABI in practice), but lets keep it under observation. - misc RT scheduling cleanups, optimizations" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) sched/rt: Add <linux/sched/rt.h> header to <linux/init_task.h> cputime: Remove irqsave from seqlock readers sched, powerpc: Fix sched.h split-up build failure cputime: Restore CPU_ACCOUNTING config defaults for PPC64 sched/rt: Move rt specific bits into new header file sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice sched: Move sched.h sysctl bits into separate header sched: Fix signedness bug in yield_to() sched: Fix select_idle_sibling() bouncing cow syndrome sched/rt: Further simplify pick_rt_task() sched/rt: Do not account zero delta_exec in update_curr_rt() cputime: Safely read cputime of full dynticks CPUs kvm: Prepare to add generic guest entry/exit callbacks cputime: Use accessors to read task cputime stats cputime: Allow dynamic switch between tick/virtual based cputime accounting cputime: Generic on-demand virtual cputime accounting cputime: Move default nsecs_to_cputime() to jiffies based cputime file cputime: Librarize per nsecs resolution cputime definitions cputime: Avoid multiplication overflow on utime scaling context_tracking: Export context state for generic vtime ... Fix up conflict in kernel/context_tracking.c due to comment additions.
| * sched: Fix select_idle_sibling() bouncing cow syndromeMike Galbraith2013-02-04
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If the previous CPU is cache affine and idle, select it. The current implementation simply traverses the sd_llc domain, taking the first idle CPU encountered, which walks buddy pairs hand in hand over the package, inflicting excruciating pain. 1 tbench pair (worst case) in a 10 core + SMT package: pre 15.22 MB/sec 1 procs post 252.01 MB/sec 1 procs Signed-off-by: Mike Galbraith <bitbucket@online.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1359371965.5783.127.camel@marge.simpson.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/fair: Set se->vruntime directly in place_entity()Viresh Kumar2013-01-24
| | | | | | | | | | | | | | | | | | | | | | | | We are first storing the new vruntime in a variable and then storing it in se->vruntime. Simply update se->vruntime directly. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Cc: linaro-dev@lists.linaro.org Cc: patches@linaro.org Cc: peterz@infradead.org Link: http://lkml.kernel.org/r/ae59db1945518d6f6250920d46eb1f1a9cc0024e.1352361704.git.viresh.kumar@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched: Fix the broken sched_rr_get_interval()Zhu Yanhai2013-01-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The caller of sched_sliced() should pass se.cfs_rq and se as the arguments, however in sched_rr_get_interval() we gave it rq.cfs_rq and se, which made the following computation obviously wrong. The change was introduced by commit: 77034937dc45 sched: fix crash in sys_sched_rr_get_interval() ... 5 years ago, while it had been the correct 'cfs_rq_of' before the commit. The change seems to be irrelevant to the commit msg, which was to return a 0 timeslice for tasks that are on an idle runqueue. So I believe that was just a plain typo. Signed-off-by: Zhu Yanhai <gaoyang.zyh@taobao.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Turner <pjt@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1357621012-15039-1-git-send-email-gaoyang.zyh@taobao.com [ Since this is an ABI and an old bug, we'll test this via a slow upstream route, to hopefully discover any app breakage. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Fix warning in kernel/sched/fair.cArnd Bergmann2013-01-25
|/ | | | | | | | | | | | | | | | | | | | | | a4c96ae319 "sched: Unthrottle rt runqueues in __disable_runtime()" turned the unthrottle_offline_cfs_rqs function into a static symbol, which now triggers a warning about it being potentially unused: kernel/sched/fair.c:2055:13: warning: 'unthrottle_offline_cfs_rqs' defined but not used [-Wunused-function] Marking it __maybe_unused shuts up the gcc warning and lets the compiler safely drop the function body when it's not being used. To reproduce, build the ARM bcm2835_defconfig. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Peter Boonstoppel <pboonstoppel@nvidia.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Turner <pjt@google.com> Cc: linux-arm-kernel@list.infradead.org Link: http://lkml.kernel.org/r/1359123276-15833-6-git-send-email-arnd@arndb.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: numa: ksm: fix oops in task_numa_placment()Hugh Dickins2012-12-20
| | | | | | | | | | | task_numa_placement() oopsed on NULL p->mm when task_numa_fault() got called in the handling of break_ksm() for ksmd. That might be a peculiar case, which perhaps KSM could takes steps to avoid? but it's more robust if task_numa_placement() allows for such a possibility. Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sched: numa: Fix build error if CONFIG_NUMA_BALANCING && ↵Mel Gorman2012-12-17
| | | | | | | | | | | | | | | | | !CONFIG_TRANSPARENT_HUGEPAGE Michal Hocko reported that the following build error occurs if CONFIG_NUMA_BALANCING is set without THP support kernel/sched/fair.c: In function ‘task_numa_work’: kernel/sched/fair.c:932:55: error: call to ‘__build_bug_failed’ declared with attribute error: BUILD_BUG failed The problem is that HPAGE_PMD_SHIFT triggers a BUILD_BUG() on !CONFIG_TRANSPARENT_HUGEPAGE. This patch addresses the problem. Reported-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge tag 'balancenuma-v11' of ↵Linus Torvalds2012-12-16
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma Pull Automatic NUMA Balancing bare-bones from Mel Gorman: "There are three implementations for NUMA balancing, this tree (balancenuma), numacore which has been developed in tip/master and autonuma which is in aa.git. In almost all respects balancenuma is the dumbest of the three because its main impact is on the VM side with no attempt to be smart about scheduling. In the interest of getting the ball rolling, it would be desirable to see this much merged for 3.8 with the view to building scheduler smarts on top and adapting the VM where required for 3.9. The most recent set of comparisons available from different people are mel: https://lkml.org/lkml/2012/12/9/108 mingo: https://lkml.org/lkml/2012/12/7/331 tglx: https://lkml.org/lkml/2012/12/10/437 srikar: https://lkml.org/lkml/2012/12/10/397 The results are a mixed bag. In my own tests, balancenuma does reasonably well. It's dumb as rocks and does not regress against mainline. On the other hand, Ingo's tests shows that balancenuma is incapable of converging for this workloads driven by perf which is bad but is potentially explained by the lack of scheduler smarts. Thomas' results show balancenuma improves on mainline but falls far short of numacore or autonuma. Srikar's results indicate we all suffer on a large machine with imbalanced node sizes. My own testing showed that recent numacore results have improved dramatically, particularly in the last week but not universally. We've butted heads heavily on system CPU usage and high levels of migration even when it shows that overall performance is better. There are also cases where it regresses. Of interest is that for specjbb in some configurations it will regress for lower numbers of warehouses and show gains for higher numbers which is not reported by the tool by default and sometimes missed in treports. Recently I reported for numacore that the JVM was crashing with NullPointerExceptions but currently it's unclear what the source of this problem is. Initially I thought it was in how numacore batch handles PTEs but I'm no longer think this is the case. It's possible numacore is just able to trigger it due to higher rates of migration. These reports were quite late in the cycle so I/we would like to start with this tree as it contains much of the code we can agree on and has not changed significantly over the last 2-3 weeks." * tag 'balancenuma-v11' of git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma: (50 commits) mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable mm/rmap: Convert the struct anon_vma::mutex to an rwsem mm: migrate: Account a transhuge page properly when rate limiting mm: numa: Account for failed allocations and isolations as migration failures mm: numa: Add THP migration for the NUMA working set scanning fault case build fix mm: numa: Add THP migration for the NUMA working set scanning fault case. mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node mm: sched: numa: Control enabling and disabling of NUMA balancing if !SCHED_DEBUG mm: sched: numa: Control enabling and disabling of NUMA balancing mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate mm: numa: Use a two-stage filter to restrict pages being migrated for unlikely task<->node relationships mm: numa: migrate: Set last_nid on newly allocated page mm: numa: split_huge_page: Transfer last_nid on tail page mm: numa: Introduce last_nid to the page frame sched: numa: Slowly increase the scanning period as NUMA faults are handled mm: numa: Rate limit setting of pte_numa if node is saturated mm: numa: Rate limit the amount of memory that is migrated between nodes mm: numa: Structures for Migrate On Fault per NUMA migration rate limiting mm: numa: Migrate pages handled during a pmd_numa hinting fault mm: numa: Migrate on reference policy ...
| * mm: sched: numa: Delay PTE scanning until a task is scheduled on a new nodeMel Gorman2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Due to the fact that migrations are driven by the CPU a task is running on there is no point tracking NUMA faults until one task runs on a new node. This patch tracks the first node used by an address space. Until it changes, PTE scanning is disabled and no NUMA hinting faults are trapped. This should help workloads that are short-lived, do not care about NUMA placement or have bound themselves to a single node. This takes advantage of the logic in "mm: sched: numa: Implement slow start for working set sampling" to delay when the checks are made. This will take advantage of processes that set their CPU and node bindings early in their lifetime. It will also potentially allow any initial load balancing to take place. Signed-off-by: Mel Gorman <mgorman@suse.de>
| * mm: sched: numa: Control enabling and disabling of NUMA balancingMel Gorman2012-12-11
| | | | | | | | | | | | | | | | | | | | This patch adds Kconfig options and kernel parameters to allow the enabling and disabling of automatic NUMA balancing. The existance of such a switch was and is very important when debugging problems related to transparent hugepages and we should have the same for automatic NUMA placement. Signed-off-by: Mel Gorman <mgorman@suse.de>
| * mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrateMel Gorman2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The PTE scanning rate and fault rates are two of the biggest sources of system CPU overhead with automatic NUMA placement. Ideally a proper policy would detect if a workload was properly placed, schedule and adjust the PTE scanning rate accordingly. We do not track the necessary information to do that but we at least know if we migrated or not. This patch scans slower if a page was not migrated as the result of a NUMA hinting fault up to sysctl_numa_balancing_scan_period_max which is now higher than the previous default. Once every minute it will reset the scanner in case of phase changes. This is hilariously crude and the numbers are arbitrary. Workloads will converge quite slowly in comparison to what a proper policy should be able to do. On the plus side, we will chew up less CPU for workloads that have no need for automatic balancing. Signed-off-by: Mel Gorman <mgorman@suse.de>
| * sched: numa: Slowly increase the scanning period as NUMA faults are handledMel Gorman2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the rate of scanning for an address space is controlled by the individual tasks. The next scan is simply determined by 2*p->numa_scan_period. The 2*p->numa_scan_period is arbitrary and never changes. At this point there is still no proper policy that decides if a task or process is properly placed. It just scans and assumes the next NUMA fault will place it properly. As it is assumed that pages will get properly placed over time, increase the scan window each time a fault is incurred. This is a big assumption as noted in the comments. It should be noted that changing to p->numa_scan_period will increase system CPU usage because now the scanning rate has effectively doubled. If that is a problem then the min_rate should be made 200ms instead of restoring the 2* logic. Signed-off-by: Mel Gorman <mgorman@suse.de>
| * mm: numa: Rate limit setting of pte_numa if node is saturatedMel Gorman2012-12-11
| | | | | | | | | | | | | | | | | | | | | | If there are a large number of NUMA hinting faults and all of them are resulting in migrations it may indicate that memory is just bouncing uselessly around. NUMA balancing cost is likely exceeding any benefit from locality. Rate limit the PTE updates if the node is migration rate-limited. As noted in the comments, this distorts the NUMA faulting statistics. Signed-off-by: Mel Gorman <mgorman@suse.de>
| * mm: sched: numa: Implement slow start for working set samplingPeter Zijlstra2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add a 1 second delay before starting to scan the working set of a task and starting to balance it amongst nodes. [ note that before the constant per task WSS sampling rate patch the initial scan would happen much later still, in effect that patch caused this regression. ] The theory is that short-run tasks benefit very little from NUMA placement: they come and go, and they better stick to the node they were started on. As tasks mature and rebalance to other CPUs and nodes, so does their NUMA placement have to change and so does it start to matter more and more. In practice this change fixes an observable kbuild regression: # [ a perf stat --null --repeat 10 test of ten bzImage builds to /dev/shm ] !NUMA: 45.291088843 seconds time elapsed ( +- 0.40% ) 45.154231752 seconds time elapsed ( +- 0.36% ) +NUMA, no slow start: 46.172308123 seconds time elapsed ( +- 0.30% ) 46.343168745 seconds time elapsed ( +- 0.25% ) +NUMA, 1 sec slow start: 45.224189155 seconds time elapsed ( +- 0.25% ) 45.160866532 seconds time elapsed ( +- 0.17% ) and it also fixes an observable perf bench (hackbench) regression: # perf stat --null --repeat 10 perf bench sched messaging -NUMA: -NUMA: 0.246225691 seconds time elapsed ( +- 1.31% ) +NUMA no slow start: 0.252620063 seconds time elapsed ( +- 1.13% ) +NUMA 1sec delay: 0.248076230 seconds time elapsed ( +- 1.35% ) The implementation is simple and straightforward, most of the patch deals with adding the /proc/sys/kernel/numa_balancing_scan_delay_ms tunable knob. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> [ Wrote the changelog, ran measurements, tuned the default. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
| * sched, numa, mm: Count WS scanning against present PTEs, not virtual memory ↵Mel Gorman2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ranges By accounting against the present PTEs, scanning speed reflects the actual present (mapped) memory. Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de>
| * mm: sched: numa: Implement constant, per task Working Set Sampling (WSS) ratePeter Zijlstra2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Previously, to probe the working set of a task, we'd use a very simple and crude method: mark all of its address space PROT_NONE. That method has various (obvious) disadvantages: - it samples the working set at dissimilar rates, giving some tasks a sampling quality advantage over others. - creates performance problems for tasks with very large working sets - over-samples processes with large address spaces but which only very rarely execute Improve that method by keeping a rotating offset into the address space that marks the current position of the scan, and advance it by a constant rate (in a CPU cycles execution proportional manner). If the offset reaches the last mapped address of the mm then it then it starts over at the first address. The per-task nature of the working set sampling functionality in this tree allows such constant rate, per task, execution-weight proportional sampling of the working set, with an adaptive sampling interval/frequency that goes from once per 100ms up to just once per 8 seconds. The current sampling volume is 256 MB per interval. As tasks mature and converge their working set, so does the sampling rate slow down to just a trickle, 256 MB per 8 seconds of CPU time executed. This, beyond being adaptive, also rate-limits rarely executing systems and does not over-sample on overloaded systems. [ In AutoNUMA speak, this patch deals with the effective sampling rate of the 'hinting page fault'. AutoNUMA's scanning is currently rate-limited, but it is also fundamentally single-threaded, executing in the knuma_scand kernel thread, so the limit in AutoNUMA is global and does not scale up with the number of CPUs, nor does it scan tasks in an execution proportional manner. So the idea of rate-limiting the scanning was first implemented in the AutoNUMA tree via a global rate limit. This patch goes beyond that by implementing an execution rate proportional working set sampling rate that is not implemented via a single global scanning daemon. ] [ Dan Carpenter pointed out a possible NULL pointer dereference in the first version of this patch. ] Based-on-idea-by: Andrea Arcangeli <aarcange@redhat.com> Bug-Found-By: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> [ Wrote changelog and fixed bug. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
| * mm: numa: Add fault driven placement and migrationPeter Zijlstra2012-12-11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | NOTE: This patch is based on "sched, numa, mm: Add fault driven placement and migration policy" but as it throws away all the policy to just leave a basic foundation I had to drop the signed-offs-by. This patch creates a bare-bones method for setting PTEs pte_numa in the context of the scheduler that when faulted later will be faulted onto the node the CPU is running on. In itself this does nothing useful but any placement policy will fundamentally depend on receiving hints on placement from fault context and doing something intelligent about it. Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com>
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