- 11 Feb, 2020 1 commit
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Suren Baghdasaryan authored
Issuing write() with count parameter set to 0 on any file under /proc/pressure/ will cause an OOB write because of the access to buf[buf_size-1] when NUL-termination is performed. Fix this by checking for buf_size to be non-zero. Signed-off-by:
Suren Baghdasaryan <surenb@google.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by:
Ingo Molnar <mingo@kernel.org> Acked-by:
Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/20200203212216.7076-1-surenb@google.com
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- 10 Feb, 2020 1 commit
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Mel Gorman authored
sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression The following XFS commit: 8ab39f11 ("xfs: prevent CIL push holdoff in log recovery") changed the logic from using bound workqueues to using unbound workqueues. Functionally this makes sense but it was observed at the time that the dbench performance dropped quite a lot and CPU migrations were increased. The current pattern of the task migration is straight-forward. With XFS, an IO issuer delegates work to xlog_cil_push_work ()on an unbound kworker. This runs on a nearby CPU and on completion, dbench wakes up on its old CPU as it is still idle and no migration occurs. dbench then queues the real IO on the blk_mq_requeue_work() work item which runs on a bound kworker which is forced to run on the same CPU as dbench. When IO completes, the bound kworker wakes dbench but as the kworker is a bound but, real task, the CPU is not considered idle and dbench gets migrated by select_idle_sibling() to a new CPU. dbench may ping-pong between two CPUs for a while but ultimately it starts a round-robin of all CPUs sharing the same LLC. High-frequency migration on each IO completion has poor performance overall. It has negative implications both in commication costs and power management. mpstat confirmed that at low thread counts that all CPUs sharing an LLC has low level of activity. Note that even if the CIL patch was reverted, there still would be migrations but the impact is less noticeable. It turns out that individually the scheduler, XFS, blk-mq and workqueues all made sensible decisions but in combination, the overall effect was sub-optimal. This patch special cases the IO issue/completion pattern and allows a bound kworker waker and a task wakee to stack on the same CPU if there is a strong chance they are directly related. The expectation is that the kworker is likely going back to sleep shortly. This is not guaranteed as the IO could be queued asynchronously but there is a very strong relationship between the task and kworker in this case that would justify stacking on the same CPU instead of migrating. There should be few concerns about kworker starvation given that the special casing is only when the kworker is the waker. DBench on XFS MMTests config: io-dbench4-async modified to run on a fresh XFS filesystem UMA machine with 8 cores sharing LLC 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack Amean 1 22.63 ( 0.00%) 20.54 * 9.23%* Amean 2 25.56 ( 0.00%) 23.40 * 8.44%* Amean 4 28.63 ( 0.00%) 27.85 * 2.70%* Amean 8 37.66 ( 0.00%) 37.68 ( -0.05%) Amean 64 469.47 ( 0.00%) 468.26 ( 0.26%) Stddev 1 1.00 ( 0.00%) 0.72 ( 28.12%) Stddev 2 1.62 ( 0.00%) 1.97 ( -21.54%) Stddev 4 2.53 ( 0.00%) 3.58 ( -41.19%) Stddev 8 5.30 ( 0.00%) 5.20 ( 1.92%) Stddev 64 86.36 ( 0.00%) 94.53 ( -9.46%) NUMA machine, 48 CPUs total, 24 CPUs share cache 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Amean 1 58.69 ( 0.00%) 30.21 * 48.53%* Amean 2 60.90 ( 0.00%) 35.29 * 42.05%* Amean 4 66.77 ( 0.00%) 46.55 * 30.28%* Amean 8 81.41 ( 0.00%) 68.46 * 15.91%* Amean 16 113.29 ( 0.00%) 107.79 * 4.85%* Amean 32 199.10 ( 0.00%) 198.22 * 0.44%* Amean 64 478.99 ( 0.00%) 477.06 * 0.40%* Amean 128 1345.26 ( 0.00%) 1372.64 * -2.04%* Stddev 1 2.64 ( 0.00%) 4.17 ( -58.08%) Stddev 2 4.35 ( 0.00%) 5.38 ( -23.73%) Stddev 4 6.77 ( 0.00%) 6.56 ( 3.00%) Stddev 8 11.61 ( 0.00%) 10.91 ( 6.04%) Stddev 16 18.63 ( 0.00%) 19.19 ( -3.01%) Stddev 32 38.71 ( 0.00%) 38.30 ( 1.06%) Stddev 64 100.28 ( 0.00%) 91.24 ( 9.02%) Stddev 128 186.87 ( 0.00%) 160.34 ( 14.20%) Dbench has been modified to report the time to complete a single "load file". This is a more meaningful metric for dbench that a throughput metric as the benchmark makes many different system calls that are not throughput-related Patch shows a 9.23% and 48.53% reduction in the time to process a load file with the difference partially explained by the number of CPUs sharing a LLC. In a separate run, task migrations were almost eliminated by the patch for low client counts. In case people have issue with the metric used for the benchmark, this is a comparison of the throughputs as reported by dbench on the NUMA machine. dbench4 Throughput (misleading but traditional) 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Hmean 1 321.41 ( 0.00%) 617.82 * 92.22%* Hmean 2 622.87 ( 0.00%) 1066.80 * 71.27%* Hmean 4 1134.56 ( 0.00%) 1623.74 * 43.12%* Hmean 8 1869.96 ( 0.00%) 2212.67 * 18.33%* Hmean 16 2673.11 ( 0.00%) 2806.13 * 4.98%* Hmean 32 3032.74 ( 0.00%) 3039.54 ( 0.22%) Hmean 64 2514.25 ( 0.00%) 2498.96 * -0.61%* Hmean 128 1778.49 ( 0.00%) 1746.05 * -1.82%* Note that this is somewhat specific to XFS and ext4 shows no performance difference as it does not rely on kworkers in the same way. No major problem was observed running other workloads on different machines although not all tests have completed yet. Signed-off-by:
Mel Gorman <mgorman@techsingularity.net> Signed-off-by:
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- 28 Jan, 2020 6 commits
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Vincent Guittot authored
When a running task is moved on a throttled task group and there is no other task enqueued on the CPU, the task can keep running using 100% CPU whatever the allocated bandwidth for the group and although its cfs rq is throttled. Furthermore, the group entity of the cfs_rq and its parents are not enqueued but only set as curr on their respective cfs_rqs. We have the following sequence: sched_move_task -dequeue_task: dequeue task and group_entities. -put_prev_task: put task and group entities. -sched_change_group: move task to new group. -enqueue_task: enqueue only task but not group entities because cfs_rq is throttled. -set_next_task : set task and group_entities as current sched_entity of their cfs_rq. Another impact is that the root cfs_rq runnable_load_avg at root rq stays null because the group_entities are not enqueued. This situation will stay the same until an "external" event triggers a reschedule. Let trigger it immediately instead. Signed-off-by:Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by:
Ben Segall <bsegall@google.com> Link: https://lkml.kernel.org/r/1579011236-31256-1-git-send-email-vincent.guittot@linaro.org
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Wanpeng Li authored
On a machine, CPU 0 is used for housekeeping, the other 39 CPUs in the same socket are in nohz_full mode. We can observe huge time burn in the loop for seaching nearest busy housekeeper cpu by ftrace. 2) | get_nohz_timer_target() { 2) 0.240 us | housekeeping_test_cpu(); 2) 0.458 us | housekeeping_test_cpu(); ... 2) 0.292 us | housekeeping_test_cpu(); 2) 0.240 us | housekeeping_test_cpu(); 2) 0.227 us | housekeeping_any_cpu(); 2) + 43.460 us | } This patch optimizes the searching logic by finding a nearest housekeeper CPU in the housekeeping cpumask, it can minimize the worst searching time from ~44us to < 10us in my testing. In addition, the last iterated busy housekeeper can become a random candidate while current CPU is a better fallback if it is a housekeeper. Signed-off-by:Wanpeng Li <wanpengli@tencent.com> Signed-off-by:
Frederic Weisbecker <frederic@kernel.org> Link: https://lkml.kernel.org/r/1578876627-11938-1-git-send-email-wanpengli@tencent.com
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Qais Yousef authored
The check to ensure that the new written value into cpu.uclamp.{min,max} is within range, [0:100], wasn't working because of the signed comparison 7301 if (req.percent > UCLAMP_PERCENT_SCALE) { 7302 req.ret = -ERANGE; 7303 return req; 7304 } # echo -1 > cpu.uclamp.min # cat cpu.uclamp.min 42949671.96 Cast req.percent into u64 to force the comparison to be unsigned and work as intended in capacity_from_percent(). # echo -1 > cpu.uclamp.min sh: write error: Numerical result out of range Fixes: 2480c093 ("sched/uclamp: Extend CPU's cgroup controller") Signed-off-by:Qais Yousef <qais.yousef@arm.com> Signed-off-by:
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Mel Gorman authored
The CPU load balancer balances between different domains to spread load and strives to have equal balance everywhere. Communicating tasks can migrate so they are topologically close to each other but these decisions are independent. On a lightly loaded NUMA machine, two communicating tasks pulled together at wakeup time can be pushed apart by the load balancer. In isolation, the load balancer decision is fine but it ignores the tasks data locality and the wakeup/LB paths continually conflict. NUMA balancing is also a factor but it also simply conflicts with the load balancer. This patch allows a fixed degree of imbalance of two tasks to exist between NUMA domains regardless of utilisation levels. In many cases, this prevents communicating tasks being pulled apart. It was evaluated whether the imbalance should be scaled to the domain size. However, no additional benefit was measured across a range of workloads and machines and scaling adds the risk that lower domains have to be rebalanced. While this could change again in the future, such a change should specify the use case and benefit. The most obvious impact is on netperf TCP_STREAM -- two simple communicating tasks with some softirq offload depending on the transmission rate. 2-socket Haswell machine 48 core, HT enabled netperf-tcp -- mmtests config config-network-netperf-unbound baseline lbnuma-v3 Hmean 64 568.73 ( 0.00%) 577.56 * 1.55%* Hmean 128 1089.98 ( 0.00%) 1128.06 * 3.49%* Hmean 256 2061.72 ( 0.00%) 2104.39 * 2.07%* Hmean 1024 7254.27 ( 0.00%) 7557.52 * 4.18%* Hmean 2048 11729.20 ( 0.00%) 13350.67 * 13.82%* Hmean 3312 15309.08 ( 0.00%) 18058.95 * 17.96%* Hmean 4096 17338.75 ( 0.00%) 20483.66 * 18.14%* Hmean 8192 25047.12 ( 0.00%) 27806.84 * 11.02%* Hmean 16384 27359.55 ( 0.00%) 33071.88 * 20.88%* Stddev 64 2.16 ( 0.00%) 2.02 ( 6.53%) Stddev 128 2.31 ( 0.00%) 2.19 ( 5.05%) Stddev 256 11.88 ( 0.00%) 3.22 ( 72.88%) Stddev 1024 23.68 ( 0.00%) 7.24 ( 69.43%) Stddev 2048 79.46 ( 0.00%) 71.49 ( 10.03%) Stddev 3312 26.71 ( 0.00%) 57.80 (-116.41%) Stddev 4096 185.57 ( 0.00%) 96.15 ( 48.19%) Stddev 8192 245.80 ( 0.00%) 100.73 ( 59.02%) Stddev 16384 207.31 ( 0.00%) 141.65 ( 31.67%) In this case, there was a sizable improvement to performance and a general reduction in variance. However, this is not univeral. For most machines, the impact was roughly a 3% performance gain. Ops NUMA base-page range updates 19796.00 292.00 Ops NUMA PTE updates 19796.00 292.00 Ops NUMA PMD updates 0.00 0.00 Ops NUMA hint faults 16113.00 143.00 Ops NUMA hint local faults % 8407.00 142.00 Ops NUMA hint local percent 52.18 99.30 Ops NUMA pages migrated 4244.00 1.00 Without the patch, only 52.18% of sampled accesses are local. In an earlier changelog, 100% of sampled accesses are local and indeed on most machines, this was still the case. In this specific case, the local sampled rates was 99.3% but note the "base-page range updates" and "PTE updates". The activity with the patch is negligible as were the number of faults. The small number of pages migrated were related to shared libraries. A 2-socket Broadwell showed better results on average but are not presented for brevity as the performance was similar except it showed 100% of the sampled NUMA hints were local. The patch holds up for a 4-socket Haswell, an AMD EPYC and AMD Epyc 2 machine. For dbench, the impact depends on the filesystem used and the number of clients. On XFS, there is little difference as the clients typically communicate with workqueues which have a separate class of scheduler problem at the moment. For ext4, performance is generally better, particularly for small numbers of clients as NUMA balancing activity is negligible with the patch applied. A more interesting example is the Facebook schbench which uses a number of messaging threads to communicate with worker threads. In this configuration, one messaging thread is used per NUMA node and the number of worker threads is varied. The 50, 75, 90, 95, 99, 99.5 and 99.9 percentiles for response latency is then reported. Lat 50.00th-qrtle-1 44.00 ( 0.00%) 37.00 ( 15.91%) Lat 75.00th-qrtle-1 53.00 ( 0.00%) 41.00 ( 22.64%) Lat 90.00th-qrtle-1 57.00 ( 0.00%) 42.00 ( 26.32%) Lat 95.00th-qrtle-1 63.00 ( 0.00%) 43.00 ( 31.75%) Lat 99.00th-qrtle-1 76.00 ( 0.00%) 51.00 ( 32.89%) Lat 99.50th-qrtle-1 89.00 ( 0.00%) 52.00 ( 41.57%) Lat 99.90th-qrtle-1 98.00 ( 0.00%) 55.00 ( 43.88%) Lat 50.00th-qrtle-2 42.00 ( 0.00%) 42.00 ( 0.00%) Lat 75.00th-qrtle-2 48.00 ( 0.00%) 47.00 ( 2.08%) Lat 90.00th-qrtle-2 53.00 ( 0.00%) 52.00 ( 1.89%) Lat 95.00th-qrtle-2 55.00 ( 0.00%) 53.00 ( 3.64%) Lat 99.00th-qrtle-2 62.00 ( 0.00%) 60.00 ( 3.23%) Lat 99.50th-qrtle-2 63.00 ( 0.00%) 63.00 ( 0.00%) Lat 99.90th-qrtle-2 68.00 ( 0.00%) 66.00 ( 2.94% For higher worker threads, the differences become negligible but it's interesting to note the difference in wakeup latency at low utilisation and mpstat confirms that activity was almost all on one node until the number of worker threads increase. Hackbench generally showed neutral results across a range of machines. This is different to earlier versions of the patch which allowed imbalances for higher degrees of utilisation. perf bench pipe showed negligible differences in overall performance as the differences are very close to the noise. An earlier prototype of the patch showed major regressions for NAS C-class when running with only half of the available CPUs -- 20-30% performance hits were measured at the time. With this version of the patch, the impact is negligible with small gains/losses within the noise measured. This is because the number of threads far exceeds the small imbalance the aptch cares about. Similarly, there were report of regressions for the autonuma benchmark against earlier versions but again, normal load balancing now applies for that workload. In general, the patch simply seeks to avoid unnecessary cross-node migrations in the basic case where imbalances are very small. For low utilisation communicating workloads, this patch generally behaves better with less NUMA balancing activity. For high utilisation, there is no change in behaviour. Signed-off-by:
Valentin Schneider <valentin.schneider@arm.com> Reviewed-by:
Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by:
Phil Auld <pauld@redhat.com> Tested-by:
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Peter Zijlstra (Intel) authored
The way loadavg is tracked during nohz only pays attention to the load upon entering nohz. This can be particularly noticeable if full nohz is entered while non-idle, and then the cpu goes idle and stays that way for a long time. Use the remote tick to ensure that full nohz cpus report their deltas within a reasonable time. [ swood: Added changelog and removed recheck of stopped tick. ] Signed-off-by:
Scott Wood <swood@redhat.com> Signed-off-by:
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Scott Wood authored
This will be used in the next patch to get a loadavg update from nohz cpus. The delta check is skipped because idle_sched_class doesn't update se.exec_start. Signed-off-by:
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- 20 Jan, 2020 1 commit
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Viresh Kumar authored
sched_idle_cpu() isn't used for non SMP configuration and with a recent change, we have started getting following warning: kernel/sched/fair.c:5221:12: warning: ‘sched_idle_cpu’ defined but not used [-Wunused-function] Fix that by defining sched_idle_cpu() only for SMP configurations. Fixes: 323af6de ("sched/fair: Load balance aggressively for SCHED_IDLE CPUs") Reported-by:
Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by:
Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by:
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- 17 Jan, 2020 14 commits
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Valentin Schneider authored
topology.c::get_group() relies on the assumption that non-NUMA domains do not partially overlap. Zeng Tao pointed out in [1] that such topology descriptions, while completely bogus, can end up being exposed to the scheduler. In his example (8 CPUs, 2-node system), we end up with: MC span for CPU3 == 3-7 MC span for CPU4 == 4-7 The first pass through get_group(3, sdd@MC) will result in the following sched_group list: 3 -> 4 -> 5 -> 6 -> 7 ^ / `----------------' And a later pass through get_group(4, sdd@MC) will "corrupt" that to: 3 -> 4 -> 5 -> 6 -> 7 ^ / `-----------' which will completely break things like 'while (sg != sd->groups)' when using CPU3's base sched_domain. There already are some architecture-specific checks in place such as x86/kernel/smpboot.c::topology.sane(), but this is something we can detect in the core scheduler, so it seems worthwhile to do so. Warn and abort the construction of the sched domains if such a broken topology description is detected. Note that this is somewhat expensive (O(t.c²), 't' non-NUMA topology levels and 'c' CPUs) and could be gated under SCHED_DEBUG if deemed necessary. Testing ======= Dietmar managed to reproduce this using the following qemu incantation: $ qemu-system-aarch64 -kernel ./Image -hda ./qemu-image-aarch64.img \ -append 'root=/dev/vda console=ttyAMA0 loglevel=8 sched_debug' -smp \ cores=8 --nographic -m 512 -cpu cortex-a53 -machine virt -numa \ node,cpus=0-2,nodeid=0 -numa node,cpus=3-7,nodeid=1 alongside the following drivers/base/arch_topology.c hack (AIUI wouldn't be needed if '-smp cores=X, sockets=Y' would work with qemu): 8<--- @@ -465,6 +465,9 @@ void update_siblings_masks(unsigned int cpuid) if (cpuid_topo->package_id != cpu_topo->package_id) continue; + if ((cpu < 4 && cpuid > 3) || (cpu > 3 && cpuid < 4)) + continue; + cpumask_set_cpu(cpuid, &cpu_topo->core_sibling); cpumask_set_cpu(cpu, &cpuid_topo->core_sibling); 8<--- [1]: https://lkml.kernel.org/r/1577088979-8545-1-git-send-email-prime.zeng@hisilicon.comReported-by:Zeng Tao <prime.zeng@hisilicon.com> Signed-off-by:
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Hewenliang authored
There is a spelling misake in comments of cpuidle_idle_call. Fix it. Signed-off-by:
Hewenliang <hewenliang4@huawei.com> Signed-off-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lkml.kernel.org/r/20200110025604.34373-1-hewenliang4@huawei.com
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Vincent Guittot authored
With commit bef69dd8 ("sched/cpufreq: Move the cfs_rq_util_change() call to cpufreq_update_util()") update_load_avg() has become the central point for calling cpufreq (not including the update of blocked load). This change helps to simplify further the number of calls to cpufreq_update_util() and to remove last redundant ones. With update_load_avg(), we are now sure that cpufreq_update_util() will be called after every task attachment to a cfs_rq and especially after propagating this event down to the util_avg of the root cfs_rq, which is the level that is used by cpufreq governors like schedutil to set the frequency of a CPU. The SCHED_CPUFREQ_MIGRATION flag forces an early call to cpufreq when the migration happens in a cgroup whereas util_avg of root cfs_rq is not yet updated and this call is duplicated with the one that happens immediately after when the migration event reaches the root cfs_rq. The dedicated flag SCHED_CPUFREQ_MIGRATION is now useless and can be removed. The interface of attach_entity_load_avg() can also be simplified accordingly. Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://lkml.kernel.org/r/1579083620-24943-1-git-send-email-vincent.guittot@linaro.org
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Wang Long authored
when CONFIG_PSI_DEFAULT_DISABLED set to N or the command line set psi=0, I think we should not create /proc/pressure and /proc/pressure/{io|memory|cpu}. In the future, user maybe determine whether the psi feature is enabled by checking the existence of the /proc/pressure dir or /proc/pressure/{io|memory|cpu} files. Signed-off-by:Wang Long <w@laoqinren.net> Signed-off-by:
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Peng Liu authored
commit bf475ce0 ("sched/fair: Add per-CPU min capacity to sched_group_capacity") introduced per-cpu min_capacity. commit e3d6d0cb ("sched/fair: Add sched_group per-CPU max capacity") introduced per-cpu max_capacity. In the SD_OVERLAP case, the local variable 'capacity' represents the sum of CPU capacity of all CPUs in the first sched group (sg) of the sched domain (sd). It is erroneously used to calculate sg's min and max CPU capacity. To fix this use capacity_of(cpu) instead of 'capacity'. The code which achieves this via cpu_rq(cpu)->sd->groups->sgc->capacity (for rq->sd != NULL) can be removed since it delivers the same value as capacity_of(cpu) which is currently only used for the (!rq->sd) case (see update_cpu_capacity()). An sg of the lowest sd (rq->sd or sd->child == NULL) represents a single CPU (and hence sg->sgc->capacity == capacity_of(cpu)). Signed-off-by:
Peng Liu <iwtbavbm@gmail.com> Signed-off-by:
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Peng Wang authored
Move the code of calculation for delta_sum/delta_avg to where it is really needed to be done. Signed-off-by:
Peng Wang <rocking@linux.alibaba.com> Signed-off-by:
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Alex Shi authored
Every time we call irqtime_account_process_tick() is in a interrupt, Every caller will get and assign a parameter rq = this_rq(), This is unnecessary and increase the code size a little bit. Move the rq getting action to irqtime_account_process_tick internally is better. base with this patch cputime.o 578792 bytes 577888 bytes Signed-off-by:Alex Shi <alex.shi@linux.alibaba.com> Signed-off-by:
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Yangtao Li authored
The function stop_cpus() is only used internally by the stop_machine for stop multiple cpus. Make it static. Signed-off-by:
Yangtao Li <tiny.windzz@gmail.com> Signed-off-by:
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Wei Li authored
Lengthy output of sysrq-t may take a lot of time on slow serial console with lots of processes and CPUs. So we need to reset NMI-watchdog to avoid spurious lockup messages, and we also reset softlockup watchdogs on all other CPUs since another CPU might be blocked waiting for us to process an IPI or stop_machine. Add to sysrq_sched_debug_show() as what we did in show_state_filter(). Signed-off-by:
Wei Li <liwei391@huawei.com> Signed-off-by:
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Li Guanglei authored
rq::uclamp is an array of struct uclamp_rq, make sure we clear the whole thing. Fixes: 69842cba ("sched/uclamp: Add CPU's clamp buckets refcountinga") Signed-off-by:
Li Guanglei <guanglei.li@unisoc.com> Signed-off-by:
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Qais Yousef authored
When a new cgroup is created, the effective uclamp value wasn't updated with a call to cpu_util_update_eff() that looks at the hierarchy and update to the most restrictive values. Fix it by ensuring to call cpu_util_update_eff() when a new cgroup becomes online. Without this change, the newly created cgroup uses the default root_task_group uclamp values, which is 1024 for both uclamp_{min, max}, which will cause the rq to to be clamped to max, hence cause the system to run at max frequency. The problem was observed on Ubuntu server and was reproduced on Debian and Buildroot rootfs. By default, Ubuntu and Debian create a cpu controller cgroup hierarchy and add all tasks to it - which creates enough noise to keep the rq uclamp value at max most of the time. Imitating this behavior makes the problem visible in Buildroot too which otherwise looks fine since it's a minimal userspace. Fixes: 0b60ba2d ("sched/uclamp: Propagate parent clamps") Reported-by:Doug Smythies <dsmythies@telus.net> Signed-off-by:
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Viresh Kumar authored
The fair scheduler performs periodic load balance on every CPU to check if it can pull some tasks from other busy CPUs. The duration of this periodic load balance is set to sd->balance_interval for the idle CPUs and is calculated by multiplying the sd->balance_interval with the sd->busy_factor (set to 32 by default) for the busy CPUs. The multiplication is done for busy CPUs to avoid doing load balance too often and rather spend more time executing actual task. While that is the right thing to do for the CPUs busy with SCHED_OTHER or SCHED_BATCH tasks, it may not be the optimal thing for CPUs running only SCHED_IDLE tasks. With the recent enhancements in the fair scheduler around SCHED_IDLE CPUs, we now prefer to enqueue a newly-woken task to a SCHED_IDLE CPU instead of other busy or idle CPUs. The same reasoning should be applied to the load balancer as well to make it migrate tasks more aggressively to a SCHED_IDLE CPU, as that will reduce the scheduling latency of the migrated (SCHED_OTHER) tasks. This patch makes minimal changes to the fair scheduler to do the next load balance soon after the last non SCHED_IDLE task is dequeued from a runqueue, i.e. making the CPU SCHED_IDLE. Also the sd->busy_factor is ignored while calculating the balance_interval for such CPUs. This is done to avoid delaying the periodic load balance by few hundred milliseconds for SCHED_IDLE CPUs. This is tested on ARM64 Hikey620 platform (octa-core) with the help of rt-app and it is verified, using kernel traces, that the newly SCHED_IDLE CPU does load balancing shortly after it becomes SCHED_IDLE and pulls tasks from other busy CPUs. Signed-off-by:
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Vincent Guittot authored
Similarly to calculate_imbalance() and find_busiest_group(), using the number of idle CPUs when there is only 1 CPU in the group is not efficient because we can't make a difference between a CPU running 1 task and a CPU running dozens of small tasks competing for the same CPU but not enough to overload it. More generally speaking, we should use the number of running tasks when there is the same number of idle CPUs in a group instead of blindly select the 1st one. When the groups have spare capacity and the same number of idle CPUs, we compare the number of running tasks to select the busiest group. Signed-off-by:
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Jisheng Zhang authored
After commit 9cf57731 ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work"), the percpu soft_lockup_hrtimer_cnt is not used any more, so remove it and related code. Signed-off-by:
Jisheng Zhang <Jisheng.Zhang@synaptics.com> Signed-off-by:
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- 25 Dec, 2019 9 commits
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Qais Yousef authored
Capacity Awareness refers to the fact that on heterogeneous systems (like Arm big.LITTLE), the capacity of the CPUs is not uniform, hence when placing tasks we need to be aware of this difference of CPU capacities. In such scenarios we want to ensure that the selected CPU has enough capacity to meet the requirement of the running task. Enough capacity means here that capacity_orig_of(cpu) >= task.requirement. The definition of task.requirement is dependent on the scheduling class. For CFS, utilization is used to select a CPU that has >= capacity value than the cfs_task.util. capacity_orig_of(cpu) >= cfs_task.util DL isn't capacity aware at the moment but can make use of the bandwidth reservation to implement that in a similar manner CFS uses utilization. The following patchset implements that: https://lore.kernel.org/lkml/20190506044836.2914-1-luca.abeni@santannapisa.it/ capacity_orig_of(cpu)/SCHED_CAPACITY >= dl_deadline/dl_runtime For RT we don't have a per task utilization signal and we lack any information in general about what performance requirement the RT task needs. But with the introduction of uclamp, RT tasks can now control that by setting uclamp_min to guarantee a minimum performance point. ATM the uclamp value are only used for frequency selection; but on heterogeneous systems this is not enough and we need to ensure that the capacity of the CPU is >= uclamp_min. Which is what implemented here. capacity_orig_of(cpu) >= rt_task.uclamp_min Note that by default uclamp.min is 1024, which means that RT tasks will always be biased towards the big CPUs, which make for a better more predictable behavior for the default case. Must stress that the bias acts as a hint rather than a definite placement strategy. For example, if all big cores are busy executing other RT tasks we can't guarantee that a new RT task will be placed there. On non-heterogeneous systems the original behavior of RT should be retained. Similarly if uclamp is not selected in the config. [ mingo: Minor edits to comments. ] Signed-off-by:
Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by:
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Valentin Schneider authored
task_fits_capacity() has just been made uclamp-aware, and find_energy_efficient_cpu() needs to go through the same treatment. Things are somewhat different here however - using the task max clamp isn't sufficient. Consider the following setup: The target runqueue, rq: rq.cpu_capacity_orig = 512 rq.cfs.avg.util_avg = 200 rq.uclamp.max = 768 // the max p.uclamp.max of all enqueued p's is 768 The waking task, p (not yet enqueued on rq): p.util_est = 600 p.uclamp.max = 100 Now, consider the following code which doesn't use the rq clamps: util = uclamp_task_util(p); // Does the task fit in the spare CPU capacity? cpu = cpu_of(rq); fits_capacity(util, cpu_capacity(cpu) - cpu_util(cpu)) This would lead to: util = 100; fits_capacity(100, 512 - 200) fits_capacity() would return true. However, enqueuing p on that CPU *will* cause it to become overutilized since rq clamp values are max-aggregated, so we'd remain with rq.uclamp.max = 768 which comes from the other tasks already enqueued on rq. Thus, we could select a high enough frequency to reach beyond 0.8 * 512 utilization (== overutilized) after enqueuing p on rq. What find_energy_efficient_cpu() needs here is uclamp_rq_util_with() which lets us peek at the future utilization landscape, including rq-wide uclamp values. Make find_energy_efficient_cpu() use uclamp_rq_util_with() for its fits_capacity() check. This is in line with what compute_energy() ends up using for estimating utilization. Tested-By:Quentin Perret <qperret@google.com> Signed-off-by:
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Valentin Schneider authored
task_fits_capacity() drives CPU selection at wakeup time, and is also used to detect misfit tasks. Right now it does so by comparing task_util_est() with a CPU's capacity, but doesn't take into account uclamp restrictions. There's a few interesting uses that can come out of doing this. For instance, a low uclamp.max value could prevent certain tasks from being flagged as misfit tasks, so they could merrily remain on low-capacity CPUs. Similarly, a high uclamp.min value would steer tasks towards high capacity CPUs at wakeup (and, should that fail, later steered via misfit balancing), so such "boosted" tasks would favor CPUs of higher capacity. Introduce uclamp_task_util() and make task_fits_capacity() use it. Tested-By:
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Valentin Schneider authored
The current helper returns (CPU) rq utilization with uclamp restrictions taken into account. A uclamp task utilization helper would be quite helpful, but this requires some renaming. Prepare the code for the introduction of a uclamp_task_util() by renaming the existing uclamp_util_with() to uclamp_rq_util_with(). Tested-By:
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Valentin Schneider authored
Vincent pointed out recently that the canonical type for utilization values is 'unsigned long'. Internally uclamp uses 'unsigned int' values for cache optimization, but this doesn't have to be exported to its users. Make the uclamp helpers that deal with utilization use and return unsigned long values. Tested-By:
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Valentin Schneider authored
The sole user of uclamp_util(), schedutil_cpu_util(), was made to use uclamp_util_with() instead in commit: af24bde8 ("sched/uclamp: Add uclamp support to energy_compute()") From then on, uclamp_util() has remained unused. Being a simple wrapper around uclamp_util_with(), we can get rid of it and win back a few lines. Tested-By:
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Viresh Kumar authored
There are instances where we keep searching for an idle CPU despite already having a sched-idle CPU (in find_idlest_group_cpu(), select_idle_smt() and select_idle_cpu() and then there are places where we don't necessarily do that and return a sched-idle CPU as soon as we find one (in select_idle_sibling()). This looks a bit inconsistent and it may be worth having the same policy everywhere. On the other hand, choosing a sched-idle CPU over a idle one shall be beneficial from performance and power point of view as well, as we don't need to get the CPU online from a deep idle state which wastes quite a lot of time and energy and delays the scheduling of the newly woken up task. This patch tries to simplify code around sched-idle CPU selection and make it consistent throughout. Testing is done with the help of rt-app on hikey board (ARM64 octa-core, 2 clusters, 0-3 and 4-7). The cpufreq governor was set to performance to avoid any side affects from CPU frequency. Following are the tests performed: Test 1: 1-cfs-task: A single SCHED_NORMAL task is pinned to CPU5 which runs for 2333 us out of 7777 us (so gives time for the cluster to go in deep idle state). Test 2: 1-cfs-1-idle-task: A single SCHED_NORMAL task is pinned on CPU5 and single SCHED_IDLE task is pinned on CPU6 (to make sure cluster 1 doesn't go in deep idle state). Test 3: 1-cfs-8-idle-task: A single SCHED_NORMAL task is pinned on CPU5 and eight SCHED_IDLE tasks are created which run forever (not pinned anywhere, so they run on all CPUs). Checked with kernelshark that as soon as NORMAL task sleeps, the SCHED_IDLE task starts running on CPU5. And here are the results on mean latency (in us), using the "st" tool. $ st 1-cfs-task/rt-app-cfs_thread-0.log N min max sum mean stddev 642 90 592 197180 307.134 109.906 $ st 1-cfs-1-idle-task/rt-app-cfs_thread-0.log N min max sum mean stddev 642 67 311 113850 177.336 41.4251 $ st 1-cfs-8-idle-task/rt-app-cfs_thread-0.log N min max sum mean stddev 643 29 173 41364 64.3297 13.2344 The mean latency when we need to: - wakeup from deep idle state is 307 us. - wakeup from shallow idle state is 177 us. - preempt a SCHED_IDLE task is 64 us. Signed-off-by:
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Qian Cai authored
This commit left behind an unused variable: 5443a0be ("sched: Use fair:prio_changed() instead of ad-hoc implementation") left behind an unused variable. kernel/sched/core.c: In function 'set_user_nice': kernel/sched/core.c:4507:16: warning: variable 'delta' set but not used int old_prio, delta; ^~~~~ Signed-off-by:
Qian Cai <cai@lca.pw> Signed-off-by:
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Ingo Molnar authored
Signed-off-by:
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- 23 Dec, 2019 2 commits
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Linus Torvalds authored
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfsLinus Torvalds authored
Pull vfs fixes from Al Viro: "Eric's s_inodes softlockup fixes + Jan's fix for recent regression from pipe rework" * 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: fs: call fsnotify_sb_delete after evict_inodes fs: avoid softlockups in s_inodes iterators pipe: Fix bogus dereference in iov_iter_alignment()
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- 22 Dec, 2019 6 commits
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git://git.kernel.org/pub/scm/fs/xfs/xfs-linuxLinus Torvalds authored
Pull xfs fixes from Darrick Wong: "Fix a few bugs that could lead to corrupt files, fsck complaints, and filesystem crashes: - Minor documentation fixes - Fix a file corruption due to read racing with an insert range operation. - Fix log reservation overflows when allocating large rt extents - Fix a buffer log item flags check - Don't allow administrators to mount with sunit= options that will cause later xfs_repair complaints about the root directory being suspicious because the fs geometry appeared inconsistent - Fix a non-static helper that should have been static" * tag 'xfs-5.5-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: xfs: Make the symbol 'xfs_rtalloc_log_count' static xfs: don't commit sunit/swidth updates to disk if that would cause repair failures xfs: split the sunit parameter update into two parts xfs: refactor agfl length computation function libxfs: resync with the userspace libxfs xfs: use bitops interface for buf log item AIL flag check xfs: fix log reservation overflows when allocating large rt extents xfs: stabilize insert range start boundary to avoid COW writeback race xfs: fix Sphinx documentation warning -
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4Linus Torvalds authored
Pull ext4 bug fixes from Ted Ts'o: "Ext4 bug fixes, including a regression fix" * tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: ext4: clarify impact of 'commit' mount option ext4: fix unused-but-set-variable warning in ext4_add_entry() jbd2: fix kernel-doc notation warning ext4: use RCU API in debug_print_tree ext4: validate the debug_want_extra_isize mount option at parse time ext4: reserve revoke credits in __ext4_new_inode ext4: unlock on error in ext4_expand_extra_isize() ext4: optimize __ext4_check_dir_entry() ext4: check for directory entries too close to block end ext4: fix ext4_empty_dir() for directories with holes
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git://git.kernel.dk/linux-blockLinus Torvalds authored
Pull block fixes from Jens Axboe: "Let's try this one again, this time without the compat_ioctl changes. We've got those fixed up, but that can go out next week. This contains: - block queue flush lockdep annotation (Bart) - Type fix for bsg_queue_rq() (Bart) - Three dasd fixes (Stefan, Jan) - nbd deadlock fix (Mike) - Error handling bio user map fix (Yang) - iocost fix (Tejun) - sbitmap waitqueue addition fix that affects the kyber IO scheduler (David)" * tag 'block-5.5-20191221' of git://git.kernel.dk/linux-block: sbitmap: only queue kyber's wait callback if not already active block: fix memleak when __blk_rq_map_user_iov() is failed s390/dasd: fix typo in copyright statement s390/dasd: fix memleak in path handling error case s390/dasd/cio: Interpret ccw_device_get_mdc return value correctly block: Fix a lockdep complaint triggered by request queue flushing block: Fix the type of 'sts' in bsg_queue_rq() block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT nbd: fix shutdown and recv work deadlock v2 iocost: over-budget forced IOs should schedule async delay -
git://git.kernel.org/pub/scm/virt/kvm/kvmLinus Torvalds authored
Pull KVM fixes from Paolo Bonzini: "PPC: - Fix a bug where we try to do an ultracall on a system without an ultravisor KVM: - Fix uninitialised sysreg accessor - Fix handling of demand-paged device mappings - Stop spamming the console on IMPDEF sysregs - Relax mappings of writable memslots - Assorted cleanups MIPS: - Now orphan, James Hogan is stepping down x86: - MAINTAINERS change, so long Radim and thanks for all the fish - supported CPUID fixes for AMD machines without SPEC_CTRL" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: MAINTAINERS: remove Radim from KVM maintainers MAINTAINERS: Orphan KVM for MIPS kvm: x86: Host feature SSBD doesn't imply guest feature AMD_SSBD kvm: x86: Host feature SSBD doesn't imply guest feature SPEC_CTRL_SSBD KVM: PPC: Book3S HV: Don't do ultravisor calls on systems without ultravisor KVM: arm/arm64: Properly handle faulting of device mappings KVM: arm64: Ensure 'params' is initialised when looking up sys register KVM: arm/arm64: Remove excessive permission check in kvm_arch_prepare_memory_region KVM: arm64: Don't log IMP DEF sysreg traps KVM: arm64: Sanely ratelimit sysreg messages KVM: arm/arm64: vgic: Use wrapper function to lock/unlock all vcpus in kvm_vgic_create() KVM: arm/arm64: vgic: Fix potential double free dist->spis in __kvm_vgic_destroy() KVM: arm/arm64: Get rid of unused arg in cpu_init_hyp_mode() -
git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linuxLinus Torvalds authored
Pull RISC-V fixes from Paul Walmsley: "Several fixes, and one cleanup, for RISC-V. Fixes: - Fix an error in a Kconfig file that resulted in an undefined Kconfig option "CONFIG_CONFIG_MMU" - Fix undefined Kconfig option "CONFIG_CONFIG_MMU" - Fix scratch register clearing in M-mode (affects nommu users) - Fix a mismerge on my part that broke the build for CONFIG_SPARSEMEM_VMEMMAP users Cleanup: - Move SiFive L2 cache-related code to drivers/soc, per request" * tag 'riscv/for-v5.5-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: riscv: move sifive_l2_cache.c to drivers/soc riscv: define vmemmap before pfn_to_page calls riscv: fix scratch register clearing in M-mode. riscv: Fix use of undefined config option CONFIG_CONFIG_MMU -
git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netLinus Torvalds authored
Pull networking fixes from David Miller: 1) Several nf_flow_table_offload fixes from Pablo Neira Ayuso, including adding a missing ipv6 match description. 2) Several heap overflow fixes in mwifiex from qize wang and Ganapathi Bhat. 3) Fix uninit value in bond_neigh_init(), from Eric Dumazet. 4) Fix non-ACPI probing of nxp-nci, from Stephan Gerhold. 5) Fix use after free in tipc_disc_rcv(), from Tuong Lien. 6) Enforce limit of 33 tail calls in mips and riscv JIT, from Paul Chaignon. 7) Multicast MAC limit test is off by one in qede, from Manish Chopra. 8) Fix established socket lookup race when socket goes from TCP_ESTABLISHED to TCP_LISTEN, because there lacks an intervening RCU grace period. From Eric Dumazet. 9) Don't send empty SKBs from tcp_write_xmit(), also from Eric Dumazet. 10) Fix active backup transition after link failure in bonding, from Mahesh Bandewar. 11) Avoid zero sized hash table in gtp driver, from Taehee Yoo. 12) Fix wrong interface passed to ->mac_link_up(), from Russell King. 13) Fix DSA egress flooding settings in b53, from Florian Fainelli. 14) Memory leak in gmac_setup_txqs(), from Navid Emamdoost. 15) Fix double free in dpaa2-ptp code, from Ioana Ciornei. 16) Reject invalid MTU values in stmmac, from Jose Abreu. 17) Fix refcount leak in error path of u32 classifier, from Davide Caratti. 18) Fix regression causing iwlwifi firmware crashes on boot, from Anders Kaseorg. 19) Fix inverted return value logic in llc2 code, from Chan Shu Tak. 20) Disable hardware GRO when XDP is attached to qede, frm Manish Chopra. 21) Since we encode state in the low pointer bits, dst metrics must be at least 4 byte aligned, which is not necessarily true on m68k. Add annotations to fix this, from Geert Uytterhoeven. * git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (160 commits) sfc: Include XDP packet headroom in buffer step size. sfc: fix channel allocation with brute force net: dst: Force 4-byte alignment of dst_metrics selftests: pmtu: fix init mtu value in description hv_netvsc: Fix unwanted rx_table reset net: phy: ensure that phy IDs are correctly typed mod_devicetable: fix PHY module format qede: Disable hardware gro when xdp prog is installed net: ena: fix issues in setting interrupt moderation params in ethtool net: ena: fix default tx interrupt moderation interval net/smc: unregister ib devices in reboot_event net: stmmac: platform: Fix MDIO init for platforms without PHY llc2: Fix return statement of llc_stat_ev_rx_null_dsap_xid_c (and _test_c) net: hisilicon: Fix a BUG trigered by wrong bytes_compl net: dsa: ksz: use common define for tag len s390/qeth: don't return -ENOTSUPP to userspace s390/qeth: fix promiscuous mode after reset s390/qeth: handle error due to unsupported transport mode cxgb4: fix refcount init for TC-MQPRIO offload tc-testing: initial tdc selftests for cls_u32 ...
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