bb74b7f456
While doing newidle load balancing, it is possible for new tasks to arrive, such as with pending wakeups. newidle_balance() already accounts for this by exiting the sched_domain load_balance() iteration if it detects these cases. This is very important for minimizing wakeup latency. However, if we are already in load_balance(), we may stay there for a while before returning back to newidle_balance(). This is most exacerbated if we enter a 'goto redo' loop in the LBF_ALL_PINNED case. A very straightforward workaround to this is to adjust should_we_balance() to bail out if we're doing a CPU_NEWLY_IDLE balance and new tasks are detected. This was tested with the following reproduction: - two threads that take turns sleeping and waking each other up are affined to two cores - a large number of threads with 100% utilization are pinned to all other cores Without this patch, wakeup latency was ~120us for the pair of threads, almost entirely spent in load_balance(). With this patch, wakeup latency is ~6us. Signed-off-by: Josh Don <joshdon@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20220609025515.2086253-1-joshdon@google.com |
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| .. | ||
| ems | ||
| autogroup.c | ||
| autogroup.h | ||
| clock.c | ||
| completion.c | ||
| core.c | ||
| cpuacct.c | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpufreq.c | ||
| cpufreq_schedutil.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle.c | ||
| isolation.c | ||
| loadavg.c | ||
| Makefile | ||
| membarrier.c | ||
| pelt.c | ||
| pelt.h | ||
| psi.c | ||
| rt.c | ||
| sched-pelt.h | ||
| sched.h | ||
| sec_mpam.c | ||
| sec_mpam_cpbm.h | ||
| sec_mpam_sysfs.c | ||
| sec_mpam_sysfs.h | ||
| smp.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| swait.c | ||
| topology.c | ||
| wait.c | ||
| wait_bit.c | ||