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author | Paul Turner <pjt@google.com> | 2012-10-04 13:18:29 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2012-10-24 10:27:18 +0200 |
commit | 9d85f21c94f7f7a84d0ba686c58aa6d9da58fdbb (patch) | |
tree | bec53516fbe39007b12250423b7a09e7b62184c3 /include/linux/sched.h | |
parent | 0e9e3e306c7e472bdcffa34c4c4584301eda03b3 (diff) | |
download | op-kernel-dev-9d85f21c94f7f7a84d0ba686c58aa6d9da58fdbb.zip op-kernel-dev-9d85f21c94f7f7a84d0ba686c58aa6d9da58fdbb.tar.gz |
sched: Track the runnable average on a per-task entity basis
Instead of tracking averaging the load parented by a cfs_rq, we can track
entity load directly. With the load for a given cfs_rq then being the sum
of its children.
To do this we represent the historical contribution to runnable average
within each trailing 1024us of execution as the coefficients of a
geometric series.
We can express this for a given task t as:
runnable_sum(t) = \Sum u_i * y^i, runnable_avg_period(t) = \Sum 1024 * y^i
load(t) = weight_t * runnable_sum(t) / runnable_avg_period(t)
Where: u_i is the usage in the last i`th 1024us period (approximately 1ms)
~ms and y is chosen such that y^k = 1/2. We currently choose k to be 32 which
roughly translates to about a sched period.
Signed-off-by: Paul Turner <pjt@google.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120823141506.372695337@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r-- | include/linux/sched.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 0dd42a0..418fc6d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1095,6 +1095,16 @@ struct load_weight { unsigned long weight, inv_weight; }; +struct sched_avg { + /* + * These sums represent an infinite geometric series and so are bound + * above by 1024/(1-y). Thus we only need a u32 to store them for for all + * choices of y < 1-2^(-32)*1024. + */ + u32 runnable_avg_sum, runnable_avg_period; + u64 last_runnable_update; +}; + #ifdef CONFIG_SCHEDSTATS struct sched_statistics { u64 wait_start; @@ -1155,6 +1165,9 @@ struct sched_entity { /* rq "owned" by this entity/group: */ struct cfs_rq *my_q; #endif +#ifdef CONFIG_SMP + struct sched_avg avg; +#endif }; struct sched_rt_entity { |