From: Yafang Shao <laoar.shao@gmail.com>
To: mgorman@suse.de, mingo@redhat.com, peterz@infradead.org,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, bristot@redhat.com, qianjun.kernel@gmail.com
Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
Yafang Shao <laoar.shao@gmail.com>
Subject: [PATCH 0/6] sched: support schedstats for RT sched class
Date: Tue, 1 Dec 2020 19:54:10 +0800 [thread overview]
Message-ID: <20201201115416.26515-1-laoar.shao@gmail.com> (raw)
We want to measure the latency of RT tasks in our production
environment with schedstats facility, but currently schedstats is only
supported for fair sched class. This patch enable it for RT sched class
as well.
- Structure
Before we make schedstats available for RT sched class, we should make
struct sched_statistics independent of fair sched class first.
The struct sched_statistics is the schedular statistics of a task_struct
or a task_group. So we can move it into struct task_struct and
struct task_group to achieve the goal.
Below is the detailed explaination of the change in the structs.
The struct before this patch:
struct task_struct { |-> struct sched_entity {
... | ...
struct sched_entity *se; ---| struct sched_statistics statistics;
struct sched_rt_entity *rt; ...
... ...
}; };
struct task_group { |--> se[0]->statistics : schedstats of CPU0
... |
#ifdef CONFIG_FAIR_GROUP_SCHED |
struct sched_entity **se; --|--> se[1]->statistics : schedstats of CPU1
|
#endif |
|--> se[N]->statistics : schedstats of CPUn
#ifdef CONFIG_FAIR_GROUP_SCHED
struct sched_rt_entity **rt_se; (N/A)
#endif
...
};
The '**se' in task_group is allocated in the fair sched class, which is
hard to be reused by other sched class.
The struct after this patch:
struct task_struct {
...
struct sched_statistics statistics;
...
struct sched_entity *se;
struct sched_rt_entity *rt;
...
};
struct task_group { |---> stats[0] : of CPU0
... |
struct sched_statistics **stats; --|---> stats[1] : of CPU1
... |
|---> stats[n] : of CPUn
#ifdef CONFIG_FAIR_GROUP_SCHED
struct sched_entity **se;
#endif
#ifdef CONFIG_RT_GROUP_SCHED
struct sched_rt_entity **rt_se;
#endif
...
};
After the patch it is clearly that both of se or rt_se can easily get the
sched_statistics by a task_struct or a task_group.
- Function Interface
The original prototype of the schedstats helpers are
update_stats_wait_*(struct cfs_rq *cfs_rq, struct sched_entity *se)
The cfs_rq in these helpers is used to get the rq_clock, and the se is
used to get the struct sched_statistics and the struct task_struct. In
order to make these helpers available by all sched classes, we can pass
the rq, sched_statistics and task_struct directly.
Then the new helpers are
update_stats_wait_*(struct rq *rq, struct task_struct *p,
struct sched_statistics *stats)
which are independent of fair sched class.
To avoid vmlinux growing too large or introducing ovehead when
!schedstat_enabled(), some new helpers after schedstat_enabled() are also
introduced, Suggested by Mel. These helpers are in sched/stats.c,
__update_stats_wait_*(struct rq *rq, struct task_struct *p,
struct sched_statistics *stats)
- Implementation
After we make the struct sched_statistics and the helpers of it
independent of fair sched class, we can easily use the schedstats
facility for RT sched class.
The schedstat usage in RT sched class is similar with fair sched class,
for example,
fair RT
enqueue update_stats_enqueue_fair update_stats_enqueue_rt
dequeue update_stats_dequeue_fair update_stats_dequeue_rt
put_prev_task update_stats_wait_start update_stats_wait_start
set_next_task update_stats_wait_end update_stats_wait_end
- Usage
The user can get the schedstats information in the same way in fair sched
class. For example,
fair RT
task show /proc/[pid]/sched /proc/[pid]/sched
group show cpu.stat in cgroup cpu.stat in cgroup
The sched:sched_stat_{wait, sleep, iowait, blocked, runtime} tracepoints
can be used to trace RT tasks as well.
Detailed examples of the output of schedstats for RT tasks are in patch #6.
Changes since RFC:
- improvement of schedstats helpers, per Mel.
- make struct schedstats independent of fair sched class
Yafang Shao (6):
sched: don't include stats.h in sched.h
sched, fair: use __schedstat_set() in set_next_entity()
sched: make struct sched_statistics independent of fair sched class
sched: make schedstats helpers independent of fair sched class
sched, rt: support sched_stat_runtime tracepoint for RT sched class
sched, rt: support schedstats for RT sched class
include/linux/sched.h | 3 +-
kernel/sched/core.c | 25 +++--
kernel/sched/deadline.c | 5 +-
kernel/sched/debug.c | 82 +++++++--------
kernel/sched/fair.c | 209 +++++++++++++++------------------------
kernel/sched/idle.c | 1 +
kernel/sched/rt.c | 142 +++++++++++++++++++++++++-
kernel/sched/sched.h | 9 +-
kernel/sched/stats.c | 105 ++++++++++++++++++++
kernel/sched/stats.h | 80 +++++++++++++++
kernel/sched/stop_task.c | 5 +-
11 files changed, 476 insertions(+), 190 deletions(-)
--
2.18.4
next reply other threads:[~2020-12-01 11:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 11:54 Yafang Shao [this message]
2020-12-01 11:54 ` [PATCH 1/6] sched: don't include stats.h in sched.h Yafang Shao
2020-12-01 11:54 ` [PATCH 2/6] sched, fair: use __schedstat_set() in set_next_entity() Yafang Shao
2020-12-01 12:28 ` Mel Gorman
2020-12-01 11:54 ` [PATCH 3/6] sched: make struct sched_statistics independent of fair sched class Yafang Shao
2020-12-01 12:41 ` Mel Gorman
2020-12-02 2:06 ` Yafang Shao
2020-12-01 11:54 ` [PATCH 4/6] sched: make schedstats helpers " Yafang Shao
2020-12-01 12:46 ` Mel Gorman
2020-12-02 2:04 ` Yafang Shao
2020-12-01 11:54 ` [PATCH 5/6] sched, rt: support sched_stat_runtime tracepoint for RT " Yafang Shao
2020-12-01 11:54 ` [PATCH 6/6] sched, rt: support schedstats " Yafang Shao
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