From: Martin Andersson Date: Mon, 27 Mar 2006 09:15:18 +0000 (-0800) Subject: [PATCH] sched: fix task interactivity calculation X-Git-Tag: v2.6.17-rc1~422 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=013d3868143387be99bb0373d49452eaa3c55d41;p=linux-2.6 [PATCH] sched: fix task interactivity calculation Is a truncation error in kernel/sched.c triggered when the nice value is negative. The affected code is used in the TASK_INTERACTIVE macro. The code is: #define SCALE(v1,v1_max,v2_max) \ (v1) * (v2_max) / (v1_max) which is used in this way: SCALE(TASK_NICE(p), 40, MAX_BONUS) Comments in the code says: * This part scales the interactivity limit depending on niceness. * * We scale it linearly, offset by the INTERACTIVE_DELTA delta. * Here are a few examples of different nice levels: * * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0] * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0] * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0] * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0] * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0] * * (the X axis represents the possible -5 ... 0 ... +5 dynamic * priority range a task can explore, a value of '1' means the * task is rated interactive.) However, the current code does not scale it linearly and the result differs from the given examples. If the mathematical function "floor" is used when the nice value is negative instead of the truncation one gets when using integer division, the result conforms to the documentation. Output of TASK_INTERACTIVE when using the kernel code: nice dynamic priorities -20 1 1 1 1 1 1 1 1 1 0 0 -19 1 1 1 1 1 1 1 1 0 0 0 -18 1 1 1 1 1 1 1 1 0 0 0 -17 1 1 1 1 1 1 1 1 0 0 0 -16 1 1 1 1 1 1 1 1 0 0 0 -15 1 1 1 1 1 1 1 0 0 0 0 -14 1 1 1 1 1 1 1 0 0 0 0 -13 1 1 1 1 1 1 1 0 0 0 0 -12 1 1 1 1 1 1 1 0 0 0 0 -11 1 1 1 1 1 1 0 0 0 0 0 -10 1 1 1 1 1 1 0 0 0 0 0 -9 1 1 1 1 1 1 0 0 0 0 0 -8 1 1 1 1 1 1 0 0 0 0 0 -7 1 1 1 1 1 0 0 0 0 0 0 -6 1 1 1 1 1 0 0 0 0 0 0 -5 1 1 1 1 1 0 0 0 0 0 0 -4 1 1 1 1 1 0 0 0 0 0 0 -3 1 1 1 1 0 0 0 0 0 0 0 -2 1 1 1 1 0 0 0 0 0 0 0 -1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 0 0 2 1 1 1 1 0 0 0 0 0 0 0 3 1 1 1 1 0 0 0 0 0 0 0 4 1 1 1 0 0 0 0 0 0 0 0 5 1 1 1 0 0 0 0 0 0 0 0 6 1 1 1 0 0 0 0 0 0 0 0 7 1 1 1 0 0 0 0 0 0 0 0 8 1 1 0 0 0 0 0 0 0 0 0 9 1 1 0 0 0 0 0 0 0 0 0 10 1 1 0 0 0 0 0 0 0 0 0 11 1 1 0 0 0 0 0 0 0 0 0 12 1 0 0 0 0 0 0 0 0 0 0 13 1 0 0 0 0 0 0 0 0 0 0 14 1 0 0 0 0 0 0 0 0 0 0 15 1 0 0 0 0 0 0 0 0 0 0 16 0 0 0 0 0 0 0 0 0 0 0 17 0 0 0 0 0 0 0 0 0 0 0 18 0 0 0 0 0 0 0 0 0 0 0 19 0 0 0 0 0 0 0 0 0 0 0 Output of TASK_INTERACTIVE when using "floor" nice dynamic priorities -20 1 1 1 1 1 1 1 1 1 0 0 -19 1 1 1 1 1 1 1 1 1 0 0 -18 1 1 1 1 1 1 1 1 1 0 0 -17 1 1 1 1 1 1 1 1 1 0 0 -16 1 1 1 1 1 1 1 1 0 0 0 -15 1 1 1 1 1 1 1 1 0 0 0 -14 1 1 1 1 1 1 1 1 0 0 0 -13 1 1 1 1 1 1 1 1 0 0 0 -12 1 1 1 1 1 1 1 0 0 0 0 -11 1 1 1 1 1 1 1 0 0 0 0 -10 1 1 1 1 1 1 1 0 0 0 0 -9 1 1 1 1 1 1 1 0 0 0 0 -8 1 1 1 1 1 1 0 0 0 0 0 -7 1 1 1 1 1 1 0 0 0 0 0 -6 1 1 1 1 1 1 0 0 0 0 0 -5 1 1 1 1 1 1 0 0 0 0 0 -4 1 1 1 1 1 0 0 0 0 0 0 -3 1 1 1 1 1 0 0 0 0 0 0 -2 1 1 1 1 1 0 0 0 0 0 0 -1 1 1 1 1 1 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 1 1 1 1 1 0 0 0 0 0 0 0 2 1 1 1 1 0 0 0 0 0 0 0 3 1 1 1 1 0 0 0 0 0 0 0 4 1 1 1 0 0 0 0 0 0 0 0 5 1 1 1 0 0 0 0 0 0 0 0 6 1 1 1 0 0 0 0 0 0 0 0 7 1 1 1 0 0 0 0 0 0 0 0 8 1 1 0 0 0 0 0 0 0 0 0 9 1 1 0 0 0 0 0 0 0 0 0 10 1 1 0 0 0 0 0 0 0 0 0 11 1 1 0 0 0 0 0 0 0 0 0 12 1 0 0 0 0 0 0 0 0 0 0 13 1 0 0 0 0 0 0 0 0 0 0 14 1 0 0 0 0 0 0 0 0 0 0 15 1 0 0 0 0 0 0 0 0 0 0 16 0 0 0 0 0 0 0 0 0 0 0 17 0 0 0 0 0 0 0 0 0 0 0 18 0 0 0 0 0 0 0 0 0 0 0 19 0 0 0 0 0 0 0 0 0 0 0 Signed-off-by: Martin Andersson Acked-by: Ingo Molnar Cc: Nick Piggin Cc: Mike Galbraith Cc: Peter Williams Cc: Con Kolivas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/sched.c b/kernel/sched.c index 78acdefecc..dc599c85a8 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -145,7 +145,8 @@ (v1) * (v2_max) / (v1_max) #define DELTA(p) \ - (SCALE(TASK_NICE(p), 40, MAX_BONUS) + INTERACTIVE_DELTA) + (SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \ + INTERACTIVE_DELTA) #define TASK_INTERACTIVE(p) \ ((p)->prio <= (p)->static_prio - DELTA(p))