From: Peter Zijlstra Date: Mon, 10 Apr 2017 10:47:33 +0000 (+0200) Subject: sched/fair: Fix comments X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=3841cdc31099fe3b84c93903c63e3d60348c0ea1;p=linux.git sched/fair: Fix comments Historically our periods (or p) argument in PELT denoted the number of full periods (what is now d2). However recent patches have changed this to the total decay (previously p+1), leading to a confusing discrepancy between comments and code. Try and clarify things by making periods (in code) and p (in comments) be the same thing (again). Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1e5f58081762b..d43e9ac9c3c5a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2777,18 +2777,18 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) u32 c1, c2, c3 = d3; /* y^0 == 1 */ /* - * c1 = d1 y^(p+1) + * c1 = d1 y^p */ c1 = decay_load((u64)d1, periods); /* - * p + * p-1 * c2 = 1024 \Sum y^n * n=1 * * inf inf * = 1024 ( \Sum y^n - \Sum y^n - y^0 ) - * n=0 n=p+1 + * n=0 n=p */ c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024; @@ -2808,15 +2808,15 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) * |<->|<----------------->|<--->| * ... |---x---|------| ... |------|-----x (now) * - * p - * u' = (u + d1) y^(p+1) + 1024 \Sum y^n + d3 y^0 - * n=1 + * p-1 + * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0 + * n=1 * - * = u y^(p+1) + (Step 1) + * = u y^p + (Step 1) * - * p - * d1 y^(p+1) + 1024 \Sum y^n + d3 y^0 (Step 2) - * n=1 + * p-1 + * d1 y^p + 1024 \Sum y^n + d3 y^0 (Step 2) + * n=1 */ static __always_inline u32 accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,