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2011-02-17sched: Fix wake_affine() vs RT tasksPeter Zijlstra
Commit: e51fd5e22e12b39f49b1bb60b37b300b17378a43 upstream Mike reports that since e9e9250b (sched: Scale down cpu_power due to RT tasks), wake_affine() goes funny on RT tasks due to them still having a !0 weight and wake_affine() still subtracts that from the rq weight. Since nobody should be using se->weight for RT tasks, set the value to zero. Also, since we now use ->cpu_power to normalize rq weights to account for RT cpu usage, add that factor into the imbalance computation. Reported-by: Mike Galbraith <efault@gmx.de> Tested-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1275316109.27810.22969.camel@twins> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-02-17sched, cgroup: Fixup broken cgroup movementPeter Zijlstra
Commit: b2b5ce022acf5e9f52f7b78c5579994fdde191d4 upstream Dima noticed that we fail to correct the ->vruntime of sleeping tasks when we move them between cgroups. Reported-by: Dima Zavin <dima@android.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Mike Galbraith <efault@gmx.de> LKML-Reference: <1287150604.29097.1513.camel@twins> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-02-17sched: Do not account irq time to current taskVenkatesh Pallipadi
Commit: 305e6835e05513406fa12820e40e4a8ecb63743c upstream Scheduler accounts both softirq and interrupt processing times to the currently running task. This means, if the interrupt processing was for some other task in the system, then the current task ends up being penalized as it gets shorter runtime than otherwise. Change sched task accounting to acoount only actual task time from currently running task. Now update_curr(), modifies the delta_exec to depend on rq->clock_task. Note that this change only handles CONFIG_IRQ_TIME_ACCOUNTING case. We can extend this to CONFIG_VIRT_CPU_ACCOUNTING with minimal effort. But, thats for later. This change will impact scheduling behavior in interrupt heavy conditions. Tested on a 4-way system with eth0 handled by CPU 2 and a network heavy task (nc) running on CPU 3 (and no RSS/RFS). With that I have CPU 2 spending 75%+ of its time in irq processing. CPU 3 spending around 35% time running nc task. Now, if I run another CPU intensive task on CPU 2, without this change /proc/<pid>/schedstat shows 100% of time accounted to this task. With this change, it rightly shows less than 25% accounted to this task as remaining time is actually spent on irq processing. Signed-off-by: Venkatesh Pallipadi <venki@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1286237003-12406-7-git-send-email-venki@google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-02-17sched: suppress RCU lockdep splat in task_fork_fairPaul E. McKenney
Commit: b0a0f667a349247bd7f05f806b662a25653822bc upstream > =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > /home/greearb/git/linux.wireless-testing/kernel/sched.c:618 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 1 > 1 lock held by ifup/23517: > #0: (&rq->lock){-.-.-.}, at: [<c042f782>] task_fork_fair+0x3b/0x108 > > stack backtrace: > Pid: 23517, comm: ifup Not tainted 2.6.36-rc6-wl+ #5 > Call Trace: > [<c075e219>] ? printk+0xf/0x16 > [<c0455842>] lockdep_rcu_dereference+0x74/0x7d > [<c0426854>] task_group+0x6d/0x79 > [<c042686e>] set_task_rq+0xe/0x57 > [<c042f79e>] task_fork_fair+0x57/0x108 > [<c042e965>] sched_fork+0x82/0xf9 > [<c04334b3>] copy_process+0x569/0xe8e > [<c0433ef0>] do_fork+0x118/0x262 > [<c076302f>] ? do_page_fault+0x16a/0x2cf > [<c044b80c>] ? up_read+0x16/0x2a > [<c04085ae>] sys_clone+0x1b/0x20 > [<c04030a5>] ptregs_clone+0x15/0x30 > [<c0402f1c>] ? sysenter_do_call+0x12/0x38 Here a newly created task is having its runqueue assigned. The new task is not yet on the tasklist, so cannot go away. This is therefore a false positive, suppress with an RCU read-side critical section. Reported-by: Ben Greear <greearb@candelatech.com Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Ben Greear <greearb@candelatech.com Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Fix select_idle_sibling() logic in select_task_rq_fair()Suresh Siddha
commit 99bd5e2f245d8cd17d040c82d40becdb3efd9b69 upstream Issues in the current select_idle_sibling() logic in select_task_rq_fair() in the context of a task wake-up: a) Once we select the idle sibling, we use that domain (spanning the cpu that the task is currently woken-up and the idle sibling that we found) in our wake_affine() decisions. This domain is completely different from the domain(we are supposed to use) that spans the cpu that the task currently woken-up and the cpu where the task previously ran. b) We do select_idle_sibling() check only for the cpu that the task is currently woken-up on. If select_task_rq_fair() selects the previously run cpu for waking the task, doing a select_idle_sibling() check for that cpu also helps and we don't do this currently. c) In the scenarios where the cpu that the task is woken-up is busy but with its HT siblings are idle, we are selecting the task be woken-up on the idle HT sibling instead of a core that it previously ran and currently completely idle. i.e., we are not taking decisions based on wake_affine() but directly selecting an idle sibling that can cause an imbalance at the SMT/MC level which will be later corrected by the periodic load balancer. Fix this by first going through the load imbalance calculations using wake_affine() and once we make a decision of woken-up cpu vs previously-ran cpu, then choose a possible idle sibling for waking up the task on. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1270079265.7835.8.camel@sbs-t61.sc.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Pre-compute cpumask_weight(sched_domain_span(sd))Peter Zijlstra
commit 669c55e9f99b90e46eaa0f98a67ec53d46dc969a upstream Dave reported that his large SPARC machines spend lots of time in hweight64(), try and optimize some of those needless cpumask_weight() invocations (esp. with the large offstack cpumasks these are very expensive indeed). Reported-by: David Miller <davem@davemloft.net> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Fix select_idle_sibling()Mike Galbraith
commit 8b911acdf08477c059d1c36c21113ab1696c612b upstream Don't bother with selection when the current cpu is idle. Recent load balancing changes also make it no longer necessary to check wake_affine() success before returning the selected sibling, so we now always use it. Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1268301369.6785.36.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Fix vmark regression on big machinesMike Galbraith
commit 50b926e439620c469565e8be0f28be78f5fca1ce upstream SD_PREFER_SIBLING is set at the CPU domain level if power saving isn't enabled, leading to many cache misses on large machines as we traverse looking for an idle shared cache to wake to. Change the enabler of select_idle_sibling() to SD_SHARE_PKG_RESOURCES, and enable same at the sibling domain level. Reported-by: Lin Ming <ming.m.lin@intel.com> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1262612696.15495.15.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: More generic WAKE_AFFINE vs select_idle_sibling()Peter Zijlstra
commit fe3bcfe1f6c1fc4ea7706ac2d05e579fd9092682 upstream Instead of only considering SD_WAKE_AFFINE | SD_PREFER_SIBLING domains also allow all SD_PREFER_SIBLING domains below a SD_WAKE_AFFINE domain to change the affinity target. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091112145610.909723612@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Cleanup select_task_rq_fair()Peter Zijlstra
commit a50bde5130f65733142b32975616427d0ea50856 upstream Clean up the new affine to idle sibling bits while trying to grok them. Should not have any function differences. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091112145610.832503781@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: apply RCU protection to wake_affine()Daniel J Blueman
commit f3b577dec1f2ce32d2db6d2ca6badff7002512af upstream The task_group() function returns a pointer that must be protected by either RCU, the ->alloc_lock, or the cgroup lock (see the rcu_dereference_check() in task_subsys_state(), which is invoked by task_group()). The wake_affine() function currently does none of these, which means that a concurrent update would be within its rights to free the structure returned by task_group(). Because wake_affine() uses this structure only to compute load-balancing heuristics, there is no reason to acquire either of the two locks. Therefore, this commit introduces an RCU read-side critical section that starts before the first call to task_group() and ends after the last use of the "tg" pointer returned from task_group(). Thanks to Li Zefan for pointing out the need to extend the RCU read-side critical section from that proposed by the original patch. Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Remove unnecessary RCU exclusionPeter Zijlstra
commit fb58bac5c75bfff8bbf7d02071a10a62f32fe28b upstream As Nick pointed out, and realized by myself when doing: sched: Fix balance vs hotplug race the patch: sched: for_each_domain() vs RCU is wrong, sched_domains are freed after synchronize_sched(), which means disabling preemption is enough. Reported-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Fix rq->clock synchronization when migrating tasksPeter Zijlstra
commit 861d034ee814917a83bd5de4b26e3b8336ddeeb8 upstream sched_fork() -- we do task placement in ->task_fork_fair() ensure we update_rq_clock() so we work with current time. We leave the vruntime in relative state, so the time delay until wake_up_new_task() doesn't matter. wake_up_new_task() -- Since task_fork_fair() left p->vruntime in relative state we can safely migrate, the activate_task() on the remote rq will call update_rq_clock() and causes the clock to be synced (enough). Tested-by: Jack Daniel <wanders.thirst@gmail.com> Tested-by: Philby John <pjohn@mvista.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1281002322.1923.1708.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Fix TASK_WAKING vs fork deadlockPeter Zijlstra
commit 0017d735092844118bef006696a750a0e4ef6ebd upstream Oleg noticed a few races with the TASK_WAKING usage on fork. - since TASK_WAKING is basically a spinlock, it should be IRQ safe - since we set TASK_WAKING (*) without holding rq->lock it could be there still is a rq->lock holder, thereby not actually providing full serialization. (*) in fact we clear PF_STARTING, which in effect enables TASK_WAKING. Cure the second issue by not setting TASK_WAKING in sched_fork(), but only temporarily in wake_up_new_task() while calling select_task_rq(). Cure the first by holding rq->lock around the select_task_rq() call, this will disable IRQs, this however requires that we push down the rq->lock release into select_task_rq_fair()'s cgroup stuff. Because select_task_rq_fair() still needs to drop the rq->lock we cannot fully get rid of TASK_WAKING. Reported-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Extend enqueue_task to allow head queueingThomas Gleixner
commit ea87bb7853168434f4a82426dd1ea8421f9e604d upstream The ability of enqueueing a task to the head of a SCHED_FIFO priority list is required to fix some violations of POSIX scheduling policy. Extend the related functions with a "head" argument. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Tested-by: Carsten Emde <cbe@osadl.org> Tested-by: Mathias Weber <mathias.weber.mw1@roche.com> LKML-Reference: <20100120171629.734886007@linutronix.de> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Remove the cfs_rq dependency from set_task_cpu()Peter Zijlstra
commit 88ec22d3edb72b261f8628226cd543589a6d5e1b upstream In order to remove the cfs_rq dependency from set_task_cpu() we need to ensure the task is cfs_rq invariant for all callsites. The simple approach is to substract cfs_rq->min_vruntime from se->vruntime on dequeue, and add cfs_rq->min_vruntime on enqueue. However, this has the downside of breaking FAIR_SLEEPERS since we loose the old vruntime as we only maintain the relative position. To solve this, we observe that we only migrate runnable tasks, we do this using deactivate_task(.sleep=0) and activate_task(.wakeup=0), therefore we can restrain the min_vruntime invariance to that state. The only other case is wakeup balancing, since we want to maintain the old vruntime we cannot make it relative on dequeue, but since we don't migrate inactive tasks, we can do so right before we activate it again. This is where we need the new pre-wakeup hook, we need to call this while still holding the old rq->lock. We could fold it into ->select_task_rq(), but since that has multiple callsites and would obfuscate the locking requirements, that seems like a fudge. This leaves the fork() case, simply make sure that ->task_fork() leaves the ->vruntime in a relative state. This covers all cases where set_task_cpu() gets called, and ensures it sees a relative vruntime. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091216170518.191697025@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Sanitize fork() handlingPeter Zijlstra
commit cd29fe6f2637cc2ccbda5ac65f5332d6bf5fa3c6 upstream Currently we try to do task placement in wake_up_new_task() after we do the load-balance pass in sched_fork(). This yields complicated semantics in that we have to deal with tasks on different RQs and the set_task_cpu() calls in copy_process() and sched_fork() Rename ->task_new() to ->task_fork() and call it from sched_fork() before the balancing, this gives the policy a clear point to place the task. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-09-20sched: Protect sched_rr_get_param() access to task->sched_classThomas Gleixner
commit dba091b9e3522b9d32fc9975e48d3b69633b45f0 upstream sched_rr_get_param calls task->sched_class->get_rr_interval(task) without protection against a concurrent sched_setscheduler() call which modifies task->sched_class. Serialize the access with task_rq_lock(task) and hand the rq pointer into get_rr_interval() as it's needed at least in the sched_fair implementation. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> LKML-Reference: <alpine.LFD.2.00.0912090930120.3089@localhost.localdomain> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-01-28sched: Fix missing sched tunable recalculation on cpu add/removeChristian Ehrhardt
commit 0bcdcf28c979869f44e05121b96ff2cfb05bd8e6 upstream. Based on Peter Zijlstras patch suggestion this enables recalculation of the scheduler tunables in response of a change in the number of cpus. It also adds a max of eight cpus that are considered in that scaling. Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1259579808-11357-2-git-send-email-ehrhardt@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-01-06sched: Select_task_rq_fair() must honour SD_LOAD_BALANCEPeter Zijlstra
commit e4f4288842ee12747e10c354d72be7d424c0b627 upstream. We should skip !SD_LOAD_BALANCE domains. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091216170517.653578430@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-12-18sched: Fix affinity logic in select_task_rq_fair()Mike Galbraith
commit fd210738f6601d0fb462df9a2fe5a41896ff6a8f upstream. Ingo Molnar reported: [ 26.804000] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/10 [ 26.808000] caller is vmstat_update+0x26/0x70 [ 26.812000] Pid: 10, comm: events/1 Not tainted 2.6.32-rc5 #6887 [ 26.816000] Call Trace: [ 26.820000] [<c1924a24>] ? printk+0x28/0x3c [ 26.824000] [<c13258a0>] debug_smp_processor_id+0xf0/0x110 [ 26.824000] mount used greatest stack depth: 1464 bytes left [ 26.828000] [<c111d086>] vmstat_update+0x26/0x70 [ 26.832000] [<c1086418>] worker_thread+0x188/0x310 [ 26.836000] [<c10863b7>] ? worker_thread+0x127/0x310 [ 26.840000] [<c108d310>] ? autoremove_wake_function+0x0/0x60 [ 26.844000] [<c1086290>] ? worker_thread+0x0/0x310 [ 26.848000] [<c108cf0c>] kthread+0x7c/0x90 [ 26.852000] [<c108ce90>] ? kthread+0x0/0x90 [ 26.856000] [<c100c0a7>] kernel_thread_helper+0x7/0x10 [ 26.860000] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/10 [ 26.864000] caller is vmstat_update+0x3c/0x70 Because this commit: a1f84a3: sched: Check for an idle shared cache in select_task_rq_fair() broke ->cpus_allowed. Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: arjan@infradead.org LKML-Reference: <1257415066.12867.1.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-12-18sched: Check for an idle shared cache in select_task_rq_fair()Mike Galbraith
commit a1f84a3ab8e002159498814eaa7e48c33752b04b upstream. When waking affine, check for an idle shared cache, and if found, wake to that CPU/sibling instead of the waker's CPU. This improves pgsql+oltp ramp up by roughly 8%. Possibly more for other loads, depending on overlap. The trade-off is a roughly 1% peak downturn if tasks are truly synchronous. Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> LKML-Reference: <1256654138.17752.7.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-10-23sched: Strengthen buddies and mitigate buddy induced latenciesMike Galbraith
This patch restores the effectiveness of LAST_BUDDY in preventing pgsql+oltp from collapsing due to wakeup preemption. It also switches LAST_BUDDY to exclusively do what it does best, namely mitigate the effects of aggressive wakeup preemption, which improves vmark throughput markedly, and restores mysql+oltp scalability. Since buddies are about scalability, enable them beginning at the point where we begin expanding sched_latency, namely sched_nr_latency. Previously, buddies were cleared aggressively, which seriously reduced their effectiveness. Not clearing aggressively however, produces a small drop in mysql+oltp throughput immediately after peak, indicating that LAST_BUDDY is actually doing some harm. This is right at the point where X on the desktop in competition with another load wants low latency service. Ergo, do not enable until we need to scale. To mitigate latency induced by buddies, or by a task just missing wakeup preemption, check latency at tick time. Last hunk prevents buddies from stymieing BALANCE_NEWIDLE via CACHE_HOT_BUDDY. Supporting performance tests: tip = v2.6.32-rc5-1497-ga525b32 tipx = NO_GENTLE_FAIR_SLEEPERS NEXT_BUDDY granularity knobs = 31 knobs + 31 buddies tip+x = NO_GENTLE_FAIR_SLEEPERS granularity knobs = 31 knobs (Three run averages except where noted.) vmark: ------ tip 108466 messages per second tip+ 125307 messages per second tip+x 125335 messages per second tipx 117781 messages per second 2.6.31.3 122729 messages per second mysql+oltp: ----------- clients 1 2 4 8 16 32 64 128 256 .......................................................................................... tip 9949.89 18690.20 34801.24 34460.04 32682.88 30765.97 28305.27 25059.64 19548.08 tip+ 10013.90 18526.84 34900.38 34420.14 33069.83 32083.40 30578.30 28010.71 25605.47 tipx 9698.71 18002.70 34477.56 33420.01 32634.30 31657.27 29932.67 26827.52 21487.18 2.6.31.3 8243.11 18784.20 34404.83 33148.38 31900.32 31161.90 29663.81 25995.94 18058.86 pgsql+oltp: ----------- clients 1 2 4 8 16 32 64 128 256 .......................................................................................... tip 13686.37 26609.25 51934.28 51347.81 49479.51 45312.65 36691.91 26851.57 24145.35 tip+ (1x) 13907.85 27135.87 52951.98 52514.04 51742.52 50705.43 49947.97 48374.19 46227.94 tip+x 13906.78 27065.81 52951.19 52542.59 52176.11 51815.94 50838.90 49439.46 46891.00 tipx 13742.46 26769.81 52351.99 51891.73 51320.79 50938.98 50248.65 48908.70 46553.84 2.6.31.3 13815.35 26906.46 52683.34 52061.31 51937.10 51376.80 50474.28 49394.47 47003.25 Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-14sched: Do less agressive buddy clearingPeter Zijlstra
Yanmin reported a hackbench regression due to: > commit de69a80be32445b0a71e8e3b757e584d7beb90f7 > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Thu Sep 17 09:01:20 2009 +0200 > > sched: Stop buddies from hogging the system I really liked de69a80b, and it affecting hackbench shows I wasn't crazy ;-) So hackbench is a multi-cast, with one sender spraying multiple receivers, who in their turn don't spray back. This would be exactly the scenario that patch 'cures'. Previously we would not clear the last buddy after running the next task, allowing the sender to get back to work sooner than it otherwise ought to have been, increasing latencies for other tasks. Now, since those receivers don't poke back, they don't enforce the buddy relation, which means there's nothing to re-elect the sender. Cure this by less agressively clearing the buddy stats. Only clear buddies when they were not chosen. It should still avoid a buddy sticking around long after its served its time. Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> CC: Mike Galbraith <efault@gmx.de> LKML-Reference: <1255084986.8802.46.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-24sysctl: remove "struct file *" argument of ->proc_handlerAlexey Dobriyan
It's unused. It isn't needed -- read or write flag is already passed and sysctl shouldn't care about the rest. It _was_ used in two places at arch/frv for some reason. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-09-21Merge branch 'sched-fixes-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: sched: Simplify sys_sched_rr_get_interval() system call sched: Fix potential NULL derference of doms_cur sched: Fix raciness in runqueue_is_locked() sched: Re-add lost cpu_allowed check to sched_fair.c::select_task_rq_fair() sched: Remove unneeded indentation in sched_fair.c::place_entity()
2009-09-21sched: Simplify sys_sched_rr_get_interval() system callPeter Williams
By removing the need for it to know details of scheduling classes. This allows PlugSched to define orthogonal scheduling classes. Signed-off-by: Peter Williams <pwil3058@bigpond.net.au> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <06d1b89ee15a0eef82d7.1253496713@mudlark.pw.nest> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-19sched: Re-add lost cpu_allowed check to sched_fair.c::select_task_rq_fair()Mike Galbraith
While doing some testing, I pinned mplayer, only to find it following X around like a puppy. Looking at commit c88d591, I found a cpu_allowed check that went AWOL. I plugged it back in where it looks like it needs to go, and now when I say "sit, stay!", mplayer obeys again. 'c88d591 sched: Merge select_task_rq_fair() and sched_balance_self()' accidentally dropped the check, causing wake_affine() to pull pinned tasks - put it back. [ v2: use a cheaper version from Peter ] Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-19Merge branch 'linus' into perfcounters/coreIngo Molnar
Merge reason: Bring in tracing changes we depend on. Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-18sched: Remove unneeded indentation in sched_fair.c::place_entity()Mike Galbraith
Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1253258365.22787.33.camel@marge.simson.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-17sched: Fix SD_POWERSAVING_BALANCE|SD_PREFER_LOCAL vs SD_WAKE_AFFINEPeter Zijlstra
The SD_POWERSAVING_BALANCE|SD_PREFER_LOCAL code can break out of the domain iteration early, making us miss the SD_WAKE_AFFINE bits. Fix this by continuing iteration until there is no need for a larger domain. This also cleans up the cgroup stuff a bit, but not having two update_shares() invocations. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-17sched: Stop buddies from hogging the systemPeter Zijlstra
Clear buddies more agressively. The (theoretical, haven't actually observed any of this) problem is that when we do not select either buddy in pick_next_entity() because they are too far ahead of the left-most task, we do not clear the buddies. This means that as soon as we service the left-most task, these same buddies will be tried again on the next schedule. Now if the left-most task was a pure hog, it wouldn't have done any wakeups and it wouldn't have set buddies of its own. That leads to the old buddies dominating, which would lead to bad latencies. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-17sched: Add new wakeup preemption mode: WAKEUP_RUNNINGPeter Zijlstra
Create a new wakeup preemption mode, preempt towards tasks that run shorter on avg. It sets next buddy to be sure we actually run the task we preempted for. Test results: root@twins:~# while :; do :; done & [1] 6537 root@twins:~# while :; do :; done & [2] 6538 root@twins:~# while :; do :; done & [3] 6539 root@twins:~# while :; do :; done & [4] 6540 root@twins:/home/peter# ./latt -c4 sleep 4 Entries: 48 (clients=4) Averages: ------------------------------ Max 4750 usec Avg 497 usec Stdev 737 usec root@twins:/home/peter# echo WAKEUP_RUNNING > /debug/sched_features root@twins:/home/peter# ./latt -c4 sleep 4 Entries: 48 (clients=4) Averages: ------------------------------ Max 14 usec Avg 5 usec Stdev 3 usec Disabled by default - needs more testing. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> LKML-Reference: <new-submission>
2009-09-16sched: Rename flags to wake_flagsPeter Zijlstra
For consistencies sake, rename the argument (again). Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-16sched: Clean up the load_idx selection in select_task_rq_fairPeter Zijlstra
Clean up the code a little. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-16sched: Optimize cgroup vs wakeup a bitPeter Zijlstra
We don't need to call update_shares() for each domain we iterate, just got the largets one. However, we should call it before wake_affine() as well, so that that can use up-to-date values too. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-16sched: Implement a gentler fair-sleepers featureIngo Molnar
Add back FAIR_SLEEPERS and GENTLE_FAIR_SLEEPERS. FAIR_SLEEPERS is the old logic: credit sleepers with their sleep time. GENTLE_FAIR_SLEEPERS dampens this a bit: 50% of their sleep time gets credited. The hope here is to still give the benefits of fair-sleepers logic (quick wakeups, etc.) while not allow them to have 100% of their sleep time as if they were running. Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-16sched: Add SD_PREFER_LOCALPeter Zijlstra
And turn it on for NUMA and MC domains. This improves locality in balancing decisions by keeping up to capacity amount of tasks local before looking for idle CPUs. (and twice the capacity if SD_POWERSAVINGS_BALANCE is set.) Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Add a few SYNC hint knobs to play withPeter Zijlstra
Currently we use overlap to weaken the SYNC hint, but allow it to set the hint as well. echo NO_SYNC_WAKEUP > /debug/sched_features echo SYNC_MORE > /debug/sched_features preserves pipe-test behaviour without using the WF_SYNC hint. Worth playing with on more workloads... Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Add WF_FORKPeter Zijlstra
Avoid the cache buddies from biasing the time distribution away from fork()ers. Normally the next buddy will be the preferred scheduling target, but this makes fork()s prefer to run the new child, whereas we prefer to run the parent, since that will generate more work. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Rename sync argumentsPeter Zijlstra
In order to extend the functions to have more than 1 flag (sync), rename the argument to flags, and explicitly define a WF_ space for individual flags. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Rename select_task_rq() argumentPeter Zijlstra
In order to be able to rename the sync argument, we need to rename the current flag argument. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Tweak wake_idxPeter Zijlstra
When merging select_task_rq_fair() and sched_balance_self() we lost the use of wake_idx, restore that and set them to 0 to make wake balancing more aggressive. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Fix task affinity for select_task_rq_fairPeter Zijlstra
While merging select_task_rq_fair() and sched_balance_self() I made a mistake that leads to testing the wrong task affinty. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: for_each_domain() vs RCUPeter Zijlstra
for_each_domain() uses RCU to serialize the sched_domains, except it doesn't actually use rcu_read_lock() and instead relies on disabling preemption -> FAIL. XXX: audit other sched_domain code. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Weaken SD_POWERSAVINGS_BALANCEPeter Zijlstra
One of the problems of power-saving balancing is that under certain scenarios it is too slow and allows tons of real work to pile up. Avoid this by ignoring the powersave stuff when there's real work to be done. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Merge select_task_rq_fair() and sched_balance_self()Peter Zijlstra
The problem with wake_idle() is that is doesn't respect things like cpu_power, which means it doesn't deal well with SMT nor the recent RT interaction. To cure this, it needs to do what sched_balance_self() does, which leads to the possibility of merging select_task_rq_fair() and sched_balance_self(). Modify sched_balance_self() to: - update_shares() when walking up the domain tree, (it only called it for the top domain, but it should have done this anyway), which allows us to remove this ugly bit from try_to_wake_up(). - do wake_affine() on the smallest domain that contains both this (the waking) and the prev (the wakee) cpu for WAKE invocations. Then use the top-down balance steps it had to replace wake_idle(). This leads to the dissapearance of SD_WAKE_BALANCE and SD_WAKE_IDLE_FAR, with SD_WAKE_IDLE replaced with SD_BALANCE_WAKE. SD_WAKE_AFFINE needs SD_BALANCE_WAKE to be effective. Touch all topology bits to replace the old with new SD flags -- platforms might need re-tuning, enabling SD_BALANCE_WAKE conditionally on a NUMA distance seems like a good additional feature, magny-core and small nehalem systems would want this enabled, systems with slow interconnects would not. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Hook sched_balance_self() into sched_class::select_task_rq()Peter Zijlstra
Rather ugly patch to fully place the sched_balance_self() code inside the fair class. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Move sched_balance_self() into sched_fair.cPeter Zijlstra
Move the sched_balance_self() code into sched_fair.c This facilitates the merger of sched_balance_self() and sched_fair::select_task_rq(). Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-15sched: Complete buddy switchesMike Galbraith
Add a NEXT_BUDDY feature flag to aid in debugging. Signed-off-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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