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-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.
-
-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
-12 which was in the kernel from 2.6.13-2.6.19 (version 13 never saw a kernel
-release). Some counters make more sense to be per-runqueue; other to be
-per-domain. Note that domains (and their associated information) will only
-be pertinent and available on machines utilizing CONFIG_SMP.
-
-In version 14 of schedstat, there is at least one level of domain
-statistics for each cpu listed, and there may well be more than one
-domain. Domains have no particular names in this implementation, but
-the highest numbered one typically arbitrates balancing across all the
-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.
-
-These fields are counters, and only increment. Programs which make use
-of these will need to start with a baseline observation and then calculate
-the change in the counters at each subsequent observation. A perl script
-which does this for many of the fields is available at
-
- http://eaglet.rain.com/rick/linux/schedstat/
-
-Note that any such script will necessarily be version-specific, as the main
-reason to change versions is changes in the output format. For those wishing
-to write their own scripts, the fields are described here.
-
-CPU statistics
---------------
-cpu<N> 1 2 3 4 5 6 7 8 9
-
-First field is a sched_yield() statistic:
- 1) # of times sched_yield() was called
-
-Next three are schedule() statistics:
- 2) This field is a legacy array expiration count field used in the O(1)
- scheduler. We kept it for ABI compatibility, but it is always set to zero.
- 3) # of times schedule() was called
- 4) # of times schedule() left the processor idle
-
-Next two are try_to_wake_up() statistics:
- 5) # of times try_to_wake_up() was called
- 6) # of times try_to_wake_up() was called to wake up the local cpu
-
-Next three are statistics describing scheduling latency:
- 7) sum of all time spent running by tasks on this processor (in jiffies)
- 8) sum of all time spent waiting to run by tasks on this processor (in
- jiffies)
- 9) # of timeslices run on this cpu
-
-
-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.)
-
-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
-
-The first field is a bit mask indicating what cpus this domain operates over.
-
-The next 24 are a variety of load_balance() statistics in grouped into types
-of idleness (idle, busy, and newly idle):
-
- 1) # of times in this domain load_balance() was called when the
- cpu was idle
- 2) # of times in this domain load_balance() checked but found
- the load did not require balancing when the cpu was idle
- 3) # of times in this domain load_balance() 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
- load_balance() in this domain when the cpu was idle
- 5) # 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
- the target task was cache-hot when idle
- 7) # of times in this domain load_balance() 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
- cpu was idle but no busier group was found
-
- 9) # of times in this domain load_balance() was called when the
- cpu was busy
- 10) # of times in this domain load_balance() checked but found the
- load did not require balancing when busy
- 11) # of times in this domain load_balance() 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
- load_balance() 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 load_balance() 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 load_balance() was called when the
- cpu was just becoming idle
- 18) # of times in this domain load_balance() checked but found the
- load did not require balancing when the cpu was just becoming idle
- 19) # of times in this domain load_balance() 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
- load_balance() 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
- target task was cache-hot when just becoming idle
- 23) # of times in this domain load_balance() 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
- 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
-
- 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
-
- 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
-
- Next three are try_to_wake_up() statistics:
- 34) # 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
- 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
-
-/proc/<pid>/schedstat
-----------------
-schedstats also adds a new /proc/<pid>/schedstat file to include some of
-the same information on a per-process level. There are three fields in
-this file correlating for that process to:
- 1) time spent on the cpu
- 2) time spent waiting on a runqueue
- 3) # of timeslices run on this cpu
-
-A program could be easily written to make use of these extra fields to
-report on how well a particular process or set of processes is faring
-under the scheduler's policies. A simple version of such a program is
-available at
- http://eaglet.rain.com/rick/linux/schedstat/v12/latency.c