| Message ID | 20210327101254.56872-1-laoar.shao@gmail.com |
|---|---|
| Headers | show |
| Series | sched: support schedstats for RT sched class | expand |
On Sat, Mar 27, 2021 at 6:13 PM Yafang Shao <laoar.shao@gmail.com> wrote: > > 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. In order to support if for other sched > classes, we should make it independent of fair sched class. The struct > sched_statistics is the schedular statistics of a task_struct or a > task_group, both of which are independent of sched class. So we can move > struct sched_statistics into struct task_struct and struct task_group to > achieve the goal. > > After the patchset, schestats are orgnized as follows, > 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 > ... > }; > > The sched_statistics members may be frequently modified when schedstats is > enabled, in order to avoid impacting on random data which may in the same > cacheline with them, the struct sched_statistics is defined as cacheline > aligned. > > Then we can use schedstats to trace RT tasks as well, for example, > Interface File > task schedstats : /proc/[pid]/sched > group schedstats: /proc/sched_debug > tracepoints : sched:sched_stat_{runtime, wait, sleep, iowait, blocked} > > As PATCH #2 and #3 changes the core struct in the scheduler, so I did > 'perf bench sched pipe' to measure the sched performance before and after > the change, suggested by Mel. Below is the data, which are all in > usecs/op. > Before After > kernel.sched_schedstats=0 6.0~6.1 6.0~6.1 > kernel.sched_schedstats=1 6.2~6.4 6.2~6.4 > No obvious difference after the change. > > Changes since v1: > - Fix the build failure reported by kernel test robot. > - Add the performance data with 'perf bench sched pipe', suggested by > Mel. > - Make the struct sched_statistics cacheline aligned. > - Introduce task block time in schedstats > > Changes since RFC: > - improvement of schedstats helpers, per Mel. > - make struct schedstats independent of fair sched class > > Yafang Shao (6): > 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: introduce task block time in schedstats > sched, rt: support sched_stat_runtime tracepoint for RT sched class > sched, rt: support schedstats for RT sched class > > include/linux/sched.h | 7 +- > kernel/sched/core.c | 24 +++-- > kernel/sched/deadline.c | 4 +- > kernel/sched/debug.c | 90 +++++++++-------- > kernel/sched/fair.c | 210 ++++++++++++++++----------------------- > kernel/sched/rt.c | 143 +++++++++++++++++++++++++- > kernel/sched/sched.h | 3 + > kernel/sched/stats.c | 104 +++++++++++++++++++ > kernel/sched/stats.h | 89 +++++++++++++++++ > kernel/sched/stop_task.c | 4 +- > 10 files changed, 489 insertions(+), 189 deletions(-) > > -- > 2.18.2 > Peter, Ingo, Mel, Any comments on this version ? -- Thanks Yafang
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. In order to support if for other sched classes, we should make it independent of fair sched class. The struct sched_statistics is the schedular statistics of a task_struct or a task_group, both of which are independent of sched class. So we can move struct sched_statistics into struct task_struct and struct task_group to achieve the goal. After the patchset, schestats are orgnized as follows, 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 ... }; The sched_statistics members may be frequently modified when schedstats is enabled, in order to avoid impacting on random data which may in the same cacheline with them, the struct sched_statistics is defined as cacheline aligned. Then we can use schedstats to trace RT tasks as well, for example, Interface File task schedstats : /proc/[pid]/sched group schedstats: /proc/sched_debug tracepoints : sched:sched_stat_{runtime, wait, sleep, iowait, blocked} As PATCH #2 and #3 changes the core struct in the scheduler, so I did 'perf bench sched pipe' to measure the sched performance before and after the change, suggested by Mel. Below is the data, which are all in usecs/op. Before After kernel.sched_schedstats=0 6.0~6.1 6.0~6.1 kernel.sched_schedstats=1 6.2~6.4 6.2~6.4 No obvious difference after the change. Changes since v1: - Fix the build failure reported by kernel test robot. - Add the performance data with 'perf bench sched pipe', suggested by Mel. - Make the struct sched_statistics cacheline aligned. - Introduce task block time in schedstats Changes since RFC: - improvement of schedstats helpers, per Mel. - make struct schedstats independent of fair sched class Yafang Shao (6): 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: introduce task block time in schedstats sched, rt: support sched_stat_runtime tracepoint for RT sched class sched, rt: support schedstats for RT sched class include/linux/sched.h | 7 +- kernel/sched/core.c | 24 +++-- kernel/sched/deadline.c | 4 +- kernel/sched/debug.c | 90 +++++++++-------- kernel/sched/fair.c | 210 ++++++++++++++++----------------------- kernel/sched/rt.c | 143 +++++++++++++++++++++++++- kernel/sched/sched.h | 3 + kernel/sched/stats.c | 104 +++++++++++++++++++ kernel/sched/stats.h | 89 +++++++++++++++++ kernel/sched/stop_task.c | 4 +- 10 files changed, 489 insertions(+), 189 deletions(-)