| 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) # of times we switched to the expired queue and reused it |
| 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 |
