On Wed, May 15, 2019 at 07:23:17PM +0530, Parth Shah wrote: > Subject: [RFCv2 1/6] sched/core: Add manual jitter classification from cgroup > interface
How can this be v2 ?! I've never seen v1. > Jitter tasks are usually of less important in terms of performance > and are short/bursty in characteristics. TurboSched uses this jitter > classification to pack jitters into the already running busy cores to > keep the total idle core count high. > > The patch describes the use of UCLAMP mechanism to classify tasks. Patrick > Bellasi came up with a mechanism to classify tasks from the userspace > https://lore.kernel.org/lkml/20190402104153.25404-1-patrick.bell...@arm.com/ The canonical form is: https://lkml.kernel.org/r/$MSGID > This UCLAMP mechanism can be useful in classifying tasks as jitter. Jitters > can be classified for the cgroup by keeping util.max of the tasks as the > least(=0). This also provides benefit of giving the least frequency to > those jitter tasks, which is useful if all jitters are packed onto a > separate core. > > Use Case with UCLAMP > =================== > To create a cgroup with all the tasks classified as jitters; > > ``` > mkdir -p /sys/fs/cgroup/cpu/jitter > echo 0 > /proc/sys/kernel/sched_uclamp_util_min; > echo 0 > /sys/fs/cgroup/cpu/jitter/cpu.util.min; > echo 0 > /sys/fs/cgroup/cpu/jitter/cpu.util.max; > i=8; > ./turbo_bench -t 30 -h $i -n $i & > ./turbo_bench -t 30 -h 0 -n $i & > echo $! > /sys/fs/cgroup/cpu/jitter/cgroup.procs; > ``` > > Signed-off-by: Parth Shah <pa...@linux.ibm.com> > --- > kernel/sched/core.c | 9 +++++++++ > kernel/sched/sched.h | 1 + > 2 files changed, 10 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index d42c0f5eefa9..77aa4aee4478 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7192,6 +7192,15 @@ static int cpu_util_max_write_u64(struct > cgroup_subsys_state *css, > tg->uclamp_req[UCLAMP_MAX].value = max_value; > tg->uclamp_req[UCLAMP_MAX].bucket_id = uclamp_bucket_id(max_value); > > + /* > + * Classify the tasks belonging to the last bucket of MAX UCLAMP as > + * jitters > + */ > + if (uclamp_bucket_id(max_value) == 0) > + tg->turbo_sched_enabled = 1; > + else if (tg->turbo_sched_enabled) > + tg->turbo_sched_enabled = 0; > + > /* Update effective clamps to track the most restrictive value */ > cpu_util_update_eff(css, UCLAMP_MAX); > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index b4019012d84b..e75ffaf3ff34 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -407,6 +407,7 @@ struct task_group { > struct uclamp_se uclamp[UCLAMP_CNT]; > #endif > > + bool turbo_sched_enabled; > }; Your simple patch has 3 problems: - it limits itself; for no apparent reason; to the cgroup interface. - it is inconsistent in the terminology; pick either jitter or turbo-sched, and I think the latter is a horrid name, it wants to be 'pack' or something similar. Also, jitter really doesn't make sense given the classification. - you use '_Bool' in a composite type.
