Commit c52f14d3 authored by Luca Abeni's avatar Luca Abeni Committed by Ingo Molnar
Browse files

sched/deadline: Implement GRUB accounting 



According to the GRUB (Greedy Reclaimation of Unused Bandwidth)
reclaiming algorithm, the runtime is not decreased as "dq = -dt",
but as "dq = -Uact dt" (where Uact is the per-runqueue active
utilization).
Hence, this commit modifies the runtime accounting rule in
update_curr_dl() to implement the GRUB rule.

Tested-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: default avatarLuca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-5-git-send-email-luca.abeni@santannapisa.it


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 387e3130

kernel/sched/core.c

+2 −2
Original line number Diff line number Diff line
@@ -2423,7 +2423,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p) 
unsigned long to_ratio(u64 period, u64 runtime)

{

	if (runtime == RUNTIME_INF)

		return 1ULL << 20;

		return BW_UNIT;



	/*

	 * Doing this here saves a lot of checks in all
@@ -2433,7 +2433,7 @@ unsigned long to_ratio(u64 period, u64 runtime) 
	if (period == 0)

		return 0;



	return div64_u64(runtime << 20, period);

	return div64_u64(runtime << BW_SHIFT, period);

}



#ifdef CONFIG_SMP

kernel/sched/deadline.c

+17 −0
Original line number Diff line number Diff line
@@ -917,6 +917,22 @@ int dl_runtime_exceeded(struct sched_dl_entity *dl_se) 


extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);



/*

 * This function implements the GRUB accounting rule:

 * according to the GRUB reclaiming algorithm, the runtime is

 * not decreased as "dq = -dt", but as "dq = -Uact dt", where

 * Uact is the (per-runqueue) active utilization.

 * Since rq->dl.running_bw contains Uact * 2^BW_SHIFT, the result

 * has to be shifted right by BW_SHIFT.

 */

u64 grub_reclaim(u64 delta, struct rq *rq)

{

	delta *= rq->dl.running_bw;

	delta >>= BW_SHIFT;



	return delta;

}



/*

 * Update the current task's runtime statistics (provided it is still

 * a -deadline task and has not been removed from the dl_rq).
@@ -959,6 +975,7 @@ static void update_curr_dl(struct rq *rq) 


	sched_rt_avg_update(rq, delta_exec);



	delta_exec = grub_reclaim(delta_exec, rq);

	dl_se->runtime -= delta_exec;



throttle:

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -1496,6 +1496,8 @@ extern void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime 
extern void init_dl_task_timer(struct sched_dl_entity *dl_se);

extern void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se);



#define BW_SHIFT	20

#define BW_UNIT		(1 << BW_SHIFT)

unsigned long to_ratio(u64 period, u64 runtime);



extern void init_entity_runnable_average(struct sched_entity *se);

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