Commit 7c8cd569 authored by Swapnil Sapkal's avatar Swapnil Sapkal Committed by Peter Zijlstra
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docs: Update Schedstat version to 17 



Update the Schedstat version to 17 as more fields are added to report
different kinds of imbalances in the sched domain. Also domain field
started printing corresponding domain name.

Signed-off-by: default avatarSwapnil Sapkal <swapnil.sapkal@amd.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241220063224.17767-7-swapnil.sapkal@amd.com
parent 011b3a14

Documentation/scheduler/sched-stats.rst

+75 −51
Original line number Diff line number Diff line
@@ -2,6 +2,12 @@ 
Scheduler Statistics

====================



Version 17 of schedstats removed 'lb_imbalance' field as it has no

significance anymore and instead added more relevant fields namely

'lb_imbalance_load', 'lb_imbalance_util', 'lb_imbalance_task' and

'lb_imbalance_misfit'. The domain field prints the name of the

corresponding sched domain from this version onwards.



Version 16 of schedstats changed the order of definitions within

'enum cpu_idle_type', which changed the order of [CPU_MAX_IDLE_TYPES]

columns in show_schedstat(). In particular the position of CPU_IDLE
@@ -9,7 +15,9 @@ and __CPU_NOT_IDLE changed places. The size of the array is unchanged. 


Version 15 of schedstats dropped counters for some sched_yield:

yld_exp_empty, yld_act_empty and yld_both_empty. Otherwise, it is

identical to version 14.

identical to version 14. Details are available at



	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/scheduler/sched-stats.txt?id=1e1dbb259c79b



Version 14 of schedstats includes support for sched_domains, which hit the

mainline kernel in 2.6.20 although it is identical to the stats from version
@@ -26,7 +34,14 @@ cpus on the machine, while domain0 is the most tightly focused domain, 
sometimes balancing only between pairs of cpus.  At this time, there

are no architectures which need more than three domain levels. The first

field in the domain stats is a bit map indicating which cpus are affected

by that domain.

by that domain. Details are available at



	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/sched-stats.txt?id=b762f3ffb797c



The schedstat documentation is maintained version 10 onwards and is not

updated for version 11 and 12. The details for version 10 are available at



	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/sched-stats.txt?id=1da177e4c3f4



These fields are counters, and only increment.  Programs which make use

of these will need to start with a baseline observation and then calculate
@@ -71,88 +86,97 @@ Domain statistics 
-----------------

One of these is produced per domain for each cpu described. (Note that if

CONFIG_SMP is not defined, *no* domains are utilized and these lines

will not appear in the output.)

will not appear in the output. <name> is an extension to the domain field

that prints the name of the corresponding sched domain. It can appear in

schedstat version 17 and above, and requires CONFIG_SCHED_DEBUG.)



domain<N> <cpumask> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

domain<N> <name> <cpumask> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45



The first field is a bit mask indicating what cpus this domain operates over.



The next 24 are a variety of sched_balance_rq() statistics in grouped into types

of idleness (idle, busy, and newly idle):

The next 33 are a variety of sched_balance_rq() statistics in grouped into types

of idleness (busy, idle and newly idle):



    1)  # of times in this domain sched_balance_rq() was called when the

        cpu was busy

    2)  # of times in this domain sched_balance_rq() checked but found the

        load did not require balancing when busy

    3)  # of times in this domain sched_balance_rq() tried to move one or

        more tasks and failed, when the cpu was busy

    4)  Total imbalance in load when the cpu was busy

    5)  Total imbalance in utilization when the cpu was busy

    6)  Total imbalance in number of tasks when the cpu was busy

    7)  Total imbalance due to misfit tasks when the cpu was busy

    8)  # of times in this domain pull_task() was called when busy

    9)  # of times in this domain pull_task() was called even though the

        target task was cache-hot when busy

    10) # of times in this domain sched_balance_rq() was called but did not

        find a busier queue while the cpu was busy

    11) # of times in this domain a busier queue was found while the cpu

        was busy but no busier group was found



    12) # of times in this domain sched_balance_rq() was called when the

        cpu was idle

    2)  # of times in this domain sched_balance_rq() checked but found

    13) # of times in this domain sched_balance_rq() checked but found

        the load did not require balancing when the cpu was idle

    3)  # of times in this domain sched_balance_rq() tried to move one or

    14) # of times in this domain sched_balance_rq() tried to move one or

        more tasks and failed, when the cpu was idle

    4)  sum of imbalances discovered (if any) with each call to

        sched_balance_rq() in this domain when the cpu was idle

    5)  # of times in this domain pull_task() was called when the cpu

    15) Total imbalance in load when the cpu was idle

    16) Total imbalance in utilization when the cpu was idle

    17) Total imbalance in number of tasks when the cpu was idle

    18) Total imbalance due to misfit tasks when the cpu was idle

    19) # of times in this domain pull_task() was called when the cpu

        was idle

    6)  # of times in this domain pull_task() was called even though

    20) # of times in this domain pull_task() was called even though

        the target task was cache-hot when idle

    7)  # of times in this domain sched_balance_rq() was called but did

    21) # of times in this domain sched_balance_rq() was called but did

        not find a busier queue while the cpu was idle

    8)  # of times in this domain a busier queue was found while the

    22) # of times in this domain a busier queue was found while the

        cpu was idle but no busier group was found

    9)  # of times in this domain sched_balance_rq() was called when the

        cpu was busy

    10) # of times in this domain sched_balance_rq() checked but found the

        load did not require balancing when busy

    11) # of times in this domain sched_balance_rq() tried to move one or

        more tasks and failed, when the cpu was busy

    12) sum of imbalances discovered (if any) with each call to

        sched_balance_rq() in this domain when the cpu was busy

    13) # of times in this domain pull_task() was called when busy

    14) # of times in this domain pull_task() was called even though the

        target task was cache-hot when busy

    15) # of times in this domain sched_balance_rq() was called but did not

        find a busier queue while the cpu was busy

    16) # of times in this domain a busier queue was found while the cpu

        was busy but no busier group was found



    17) # of times in this domain sched_balance_rq() was called when the

        cpu was just becoming idle

    18) # of times in this domain sched_balance_rq() checked but found the

    23) # of times in this domain sched_balance_rq() was called when the

        was just becoming idle

    24) # of times in this domain sched_balance_rq() checked but found the

        load did not require balancing when the cpu was just becoming idle

    19) # of times in this domain sched_balance_rq() tried to move one or more

    25) # of times in this domain sched_balance_rq() tried to move one or more

        tasks and failed, when the cpu was just becoming idle

    20) sum of imbalances discovered (if any) with each call to

        sched_balance_rq() in this domain when the cpu was just becoming idle

    21) # of times in this domain pull_task() was called when newly idle

    22) # of times in this domain pull_task() was called even though the

    26) Total imbalance in load when the cpu was just becoming idle

    27) Total imbalance in utilization when the cpu was just becoming idle

    28) Total imbalance in number of tasks when the cpu was just becoming idle

    29) Total imbalance due to misfit tasks when the cpu was just becoming idle

    30) # of times in this domain pull_task() was called when newly idle

    31) # of times in this domain pull_task() was called even though the

        target task was cache-hot when just becoming idle

    23) # of times in this domain sched_balance_rq() was called but did not

    32) # of times in this domain sched_balance_rq() was called but did not

        find a busier queue while the cpu was just becoming idle

    24) # of times in this domain a busier queue was found while the cpu

    33) # of times in this domain a busier queue was found while the cpu

        was just becoming idle but no busier group was found



   Next three are active_load_balance() statistics:



    25) # of times active_load_balance() was called

    26) # of times active_load_balance() tried to move a task and failed

    27) # of times active_load_balance() successfully moved a task

    34) # of times active_load_balance() was called

    35) # of times active_load_balance() tried to move a task and failed

    36) # of times active_load_balance() successfully moved a task



   Next three are sched_balance_exec() statistics:



    28) sbe_cnt is not used

    29) sbe_balanced is not used

    30) sbe_pushed is not used

    37) sbe_cnt is not used

    38) sbe_balanced is not used

    39) sbe_pushed is not used



   Next three are sched_balance_fork() statistics:



    31) sbf_cnt is not used

    32) sbf_balanced is not used

    33) sbf_pushed is not used

    40) sbf_cnt is not used

    41) sbf_balanced is not used

    42) sbf_pushed is not used



   Next three are try_to_wake_up() statistics:



    34) # of times in this domain try_to_wake_up() awoke a task that

    43) # of times in this domain try_to_wake_up() awoke a task that

        last ran on a different cpu in this domain

    35) # of times in this domain try_to_wake_up() moved a task to the

    44) # of times in this domain try_to_wake_up() moved a task to the

        waking cpu because it was cache-cold on its own cpu anyway

    36) # of times in this domain try_to_wake_up() started passive balancing

    45) # of times in this domain try_to_wake_up() started passive balancing



/proc/<pid>/schedstat

---------------------

kernel/sched/stats.c

+1 −1
Original line number Diff line number Diff line
@@ -103,7 +103,7 @@ void __update_stats_enqueue_sleeper(struct rq *rq, struct task_struct *p, 
 * Bump this up when changing the output format or the meaning of an existing

 * format, so that tools can adapt (or abort)

 */

#define SCHEDSTAT_VERSION 16

#define SCHEDSTAT_VERSION 17



static int show_schedstat(struct seq_file *seq, void *v)

{