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Commit 2159197d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/core: Enable increased load resolution on 64-bit kernels 



Mike ran into the low load resolution limitation on his big machine.

So reenable these bits; nobody could ever reproduce/analyze the
reported power usage claim and Google has been running with this for
years as well.

Reported-by: default avatarMike Galbraith <umgwanakikbuti@gmail.com>
Tested-by: default avatarMike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e7904a28

kernel/sched/sched.h

+6 −4
Original line number Diff line number Diff line
@@ -49,11 +49,13 @@ static inline void cpu_load_update_active(struct rq *this_rq) { } 
 * and does not change the user-interface for setting shares/weights.

 *

 * We increase resolution only if we have enough bits to allow this increased

 * resolution (i.e. BITS_PER_LONG > 32). The costs for increasing resolution

 * when BITS_PER_LONG <= 32 are pretty high and the returns do not justify the

 * increased costs.

 * resolution (i.e. 64bit). The costs for increasing resolution when 32bit are

 * pretty high and the returns do not justify the increased costs.

 *

 * Really only required when CONFIG_FAIR_GROUP_SCHED is also set, but to

 * increase coverage and consistency always enable it on 64bit platforms.

 */

#if 0 /* BITS_PER_LONG > 32 -- currently broken: it increases power usage under light load  */

#ifdef CONFIG_64BIT

# define SCHED_LOAD_RESOLUTION	10

# define scale_load(w)		((w) << SCHED_LOAD_RESOLUTION)

# define scale_load_down(w)	((w) >> SCHED_LOAD_RESOLUTION)