Hi Austin,
thank you for the patch.
-----Original Message-----
> Sometimes kernel image is generated without CONFIG_SCHEDSTATS or CONFIG_SCHED_INFO.
> Where relevant commit id is f6db83479932 ("sched/stat: Simplify the sched_info accounting")
>
> - CONFIG_SCHED_INFO: KERNEL_VERSION >= LINUX(4,2,0)
> - CONFIG_SCHEDSTATS: KERNEL_VERSION < LINUX(4,2,0)
>
> Running crash-utility with above kernel image,
> "ps -l" option cannot display all processes sorted with most recently-run process.
> Also "ps -m" option cannot display all processes with timestamp.
>
> crash> ps -l or crash> ps -m
> ps: last-run timestamps do not exist in this kernel
> Usage: ps [-k|-u|-G] [-s]
> [-p|-c|-t|-[l|m][-C cpu]|-a|-g|-r|-S]
> [pid | task | command] ...
> Enter "help ps" for details.
>
> This is because output of "ps -l|-m" depends on task_struct.sched_info.last_arrival.
>
> Without CONFIG_SCHEDSTATS or CONFIG_SCHED_INFO, 'sched_info' field is not included
> in task_struct.
>
> So we make "ps -l|-m" option to access 'exec_start' field of sched_entity
> where 'exec_start' is task_struct.se.exec_start.
Could you describe what the exec_start means? When is it updated?
Checking a vmcore on hand, those values are different each other.
crash> task | grep -e exec_start -e last_arrival
exec_start = 737120183773,
last_arrival = 737112829272,
crash> task 1 | grep -e exec_start -e last_arrival
exec_start = 736519632741,
last_arrival = 736515663193,
The current last_arrival looks to be updated only by this path and
I think it's the time when a task gets a CPU:
context_switch
prepare_task_switch
sched_info_switch
sched_info_arrive
So if the meaning of the exec_start is different from last_arrival,
it would be better to have a description about it in the help text.
>
> With this patch, "ps -l|-m" option works well without CONFIG_SCHEDSTATS or
> CONFIG_SCHED_INFO.
>
> Signed-off-by: Austin Kim <austindh.kim@xxxxxxxxx>
> ---
> defs.h | 2 ++
> symbols.c | 2 ++
> task.c | 20 ++++++++++++++++----
> 3 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index bf2c59b..5dda176 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -2168,6 +2168,8 @@ struct offset_table { /* stash of commonly-used offsets */
> long sbitmap_queue_min_shallow_depth;
> long sbq_wait_state_wait_cnt;
> long sbq_wait_state_wait;
> + long task_struct_sched_entity;
> + long se_exec_start;
Normally names in this table are "struct_name_member_name", so
these should be "task_struct_se" and "sched_entity_exec_start"
respectively.
And "task_struct_se" already exists, so please fix those.
long cfs_rq_tasks_timeline;
long task_struct_se;
long sched_entity_run_node;
> };
>
> struct size_table { /* stash of commonly-used sizes */
> diff --git a/symbols.c b/symbols.c
> index ba5e274..e5abe87 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -8892,6 +8892,8 @@ dump_offset_table(char *spec, ulong makestruct)
> OFFSET(sched_rt_entity_run_list));
> fprintf(fp, " sched_info_last_arrival: %ld\n",
> OFFSET(sched_info_last_arrival));
> + fprintf(fp, " se_exec_start: %ld\n",
> + OFFSET(se_exec_start));
There are already some sched_entity members, please move this here.
fprintf(fp, " task_struct_se: %ld\n",
OFFSET(task_struct_se));
fprintf(fp, " sched_entity_run_node: %ld\n",
OFFSET(sched_entity_run_node));
fprintf(fp, " sched_entity_cfs_rq: %ld\n",
OFFSET(sched_entity_cfs_rq));
fprintf(fp, " sched_entity_my_q: %ld\n",
OFFSET(sched_entity_my_q));
fprintf(fp, " sched_entity_on_rq: %ld\n",
OFFSET(sched_entity_on_rq));
Thanks,
Kazu
> fprintf(fp, " task_struct_thread_info: %ld\n",
> OFFSET(task_struct_thread_info));
> fprintf(fp, " task_struct_stack: %ld\n",
> diff --git a/task.c b/task.c
> index 864c838..55e2312 100644
> --- a/task.c
> +++ b/task.c
> @@ -334,9 +334,15 @@ task_init(void)
> if (VALID_MEMBER(task_struct_sched_info))
> MEMBER_OFFSET_INIT(sched_info_last_arrival,
> "sched_info", "last_arrival");
> + MEMBER_OFFSET_INIT(task_struct_sched_entity, "task_struct", "se");
> + if (VALID_MEMBER(task_struct_sched_entity)) {
> + STRUCT_SIZE_INIT(sched_entity, "sched_entity");
> + MEMBER_OFFSET_INIT(se_exec_start, "sched_entity", "exec_start");
> + }
> if (VALID_MEMBER(task_struct_last_run) ||
> VALID_MEMBER(task_struct_timestamp) ||
> - VALID_MEMBER(sched_info_last_arrival)) {
> + VALID_MEMBER(sched_info_last_arrival) ||
> + VALID_MEMBER(se_exec_start)) {
> char buf[BUFSIZE];
> strcpy(buf, "alias last ps -l");
> alias_init(buf);
> @@ -3559,7 +3565,8 @@ cmd_ps(void)
> case 'm':
> if (INVALID_MEMBER(task_struct_last_run) &&
> INVALID_MEMBER(task_struct_timestamp) &&
> - INVALID_MEMBER(sched_info_last_arrival)) {
> + INVALID_MEMBER(sched_info_last_arrival) &&
> + INVALID_MEMBER(se_exec_start)) {
> error(INFO,
> "last-run timestamps do not exist in this kernel\n");
> argerrs++;
> @@ -3574,7 +3581,8 @@ cmd_ps(void)
> case 'l':
> if (INVALID_MEMBER(task_struct_last_run) &&
> INVALID_MEMBER(task_struct_timestamp) &&
> - INVALID_MEMBER(sched_info_last_arrival)) {
> + INVALID_MEMBER(sched_info_last_arrival) &&
> + INVALID_MEMBER(se_exec_start)) {
> error(INFO,
> "last-run timestamps do not exist in this kernel\n");
> argerrs++;
> @@ -6020,7 +6028,11 @@ task_last_run(ulong task)
> timestamp = tt->last_task_read ? ULONGLONG(tt->task_struct +
> OFFSET(task_struct_sched_info) +
> OFFSET(sched_info_last_arrival)) : 0;
> -
> + else if (VALID_MEMBER(se_exec_start))
> + timestamp = tt->last_task_read ? ULONGLONG(tt->task_struct +
> + OFFSET(task_struct_sched_entity) +
> + OFFSET(se_exec_start)) : 0;
> +
> return timestamp;
> }
>
> --
> 2.20.1
--
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