Commit db4551e2 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched/fair: Use full weight to __calc_delta() 



Since we now use the full weight for avg_vruntime(), also make
__calc_delta() use the full value.

Since weight is effectively NICE_0_LOAD, this is 20 bits on 64bit.
This leaves 44 bits for delta_exec, which is ~16k seconds, way longer
than any one tick would ever be, so no worry about overflow.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Tested-by: default avatarK Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: default avatarShubhang Kaushik <shubhang@os.amperecomputing.com>
Link: https://patch.msgid.link/20260219080625.183283814%40infradead.org
parent 101f3498

kernel/sched/fair.c

+7 −0
Original line number Diff line number Diff line
@@ -225,6 +225,7 @@ void __init sched_init_granularity(void) 
	update_sysctl();

}



#ifndef CONFIG_64BIT

#define WMULT_CONST	(~0U)

#define WMULT_SHIFT	32
@@ -283,6 +284,12 @@ static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight 


	return mul_u64_u32_shr(delta_exec, fact, shift);

}

#else

static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)

{

	return (delta_exec * weight) / lw->weight;

}

#endif



/*

 * delta /= w