On 27 February 2015 at 16:54, Vincent Guittot <[email protected]> wrote: > This patchset consolidates several changes in the capacity and the usage > tracking of the CPU. It provides a frequency invariant metric of the usage of > CPUs and generally improves the accuracy of load/usage tracking in the > scheduler. The frequency invariant metric is the foundation required for the > consolidation of cpufreq and implementation of a fully invariant load > tracking. > These are currently WIP and require several changes to the load balancer > (including how it will use and interprets load and capacity metrics) and > extensive validation. The frequency invariance is done with > arch_scale_freq_capacity and this patchset doesn't provide the backends of > the function which are architecture dependent. > > As discussed at LPC14, Morten and I have consolidated our changes into a > single > patchset to make it easier to review and merge. > > During load balance, the scheduler evaluates the number of tasks that a group > of CPUs can handle. The current method assumes that tasks have a fix load of > SCHED_LOAD_SCALE and CPUs have a default capacity of SCHED_CAPACITY_SCALE. > This assumption generates wrong decision by creating ghost cores or by > removing real ones when the original capacity of CPUs is different from the > default SCHED_CAPACITY_SCALE. With this patch set, we don't try anymore to > evaluate the number of available cores based on the group_capacity but instead > we evaluate the usage of a group and compare it with its capacity. > > This patchset mainly replaces the old capacity_factor method by a new one and > keeps the general policy almost unchanged. These new metrics will be also used > in later patches. > > The CPU usage is based on a running time tracking version of the current > implementation of the load average tracking. I also have a version that is > based on the new implementation proposal [1] but I haven't provide the patches > and results as [1] is still under review. I can provide change above [1] to > change how CPU usage is computed and to adapt to new mecanism. > > Change since V9 > - add a dedicated patch for removing unused capacity_orig > - update some comments and fix typo > - change the condition for actively migrating task on CPU with higher > capacity > > Change since V8 > - reorder patches > > Change since V7 > - add freq invariance for usage tracking > - add freq invariance for scale_rt > - update comments and commits' message > - fix init of utilization_avg_contrib > - fix prefer_sibling > > Change since V6 > - add group usage tracking > - fix some commits' messages > - minor fix like comments and argument order > > Change since V5 > - remove patches that have been merged since v5 : patches 01, 02, 03, 04, > 05, 07 > - update commit log and add more details on the purpose of the patches > - fix/remove useless code with the rebase on patchset [2] > - remove capacity_orig in sched_group_capacity as it is not used > - move code in the right patch > - add some helper function to factorize code > > Change since V4 > - rebase to manage conflicts with changes in selection of busiest group > > Change since V3: > - add usage_avg_contrib statistic which sums the running time of tasks on a > rq > - use usage_avg_contrib instead of runnable_avg_sum for cpu_utilization > - fix replacement power by capacity > - update some comments > > Change since V2: > - rebase on top of capacity renaming > - fix wake_affine statistic update > - rework nohz_kick_needed > - optimize the active migration of a task from CPU with reduced capacity > - rename group_activity by group_utilization and remove unused > total_utilization > - repair SD_PREFER_SIBLING and use it for SMT level > - reorder patchset to gather patches with same topics > > Change since V1: > - add 3 fixes > - correct some commit messages > - replace capacity computation by activity > - take into account current cpu capacity > > [1] https://lkml.org/lkml/2014/10/10/131 > [2] https://lkml.org/lkml/2014/7/25/589 > > Morten Rasmussen (2): > sched: Track group sched_entity usage contributions > sched: Make sched entity usage tracking scale-invariant > > Vincent Guittot (9): > sched: add utilization_avg_contrib > sched: remove frequency scaling from cpu_capacity > sched: make scale_rt invariant with frequency > sched: add per rq cpu_capacity_orig > sched: get CPU's usage statistic > sched: replace capacity_factor by usage > sched; remove unused capacity_orig from > sched: add SD_PREFER_SIBLING for SMT level > sched: move cfs task on a CPU with higher capacity > > include/linux/sched.h | 21 ++- > kernel/sched/core.c | 15 +-- > kernel/sched/debug.c | 12 +- > kernel/sched/fair.c | 366 > +++++++++++++++++++++++++++++++------------------- > kernel/sched/sched.h | 15 ++- > 5 files changed, 271 insertions(+), 158 deletions(-) > > -- > 1.9.1 >
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