sched: make the multiplication table more accurate (254753dc) · Commits · 戴 / test

do small deltas in the weight and multiplication constant table so that the worst-case numeric error is better than 1:100000000. (8 digits) the current error table is: nice mult * inv_mult error ------------------------------------------ -20: 88761 * 48388 -0.0000000065 -19: 71755 * 59856 -0.0000000037 -18: 56483 * 76040 0.0000000056 -17: 46273 * 92818 0.0000000042 -16: 36291 * 118348 -0.0000000065 -15: 29154 * 147320 -0.0000000037 -14: 23254 * 184698 -0.0000000009 -13: 18705 * 229616 -0.0000000037 -12: 14949 * 287308 -0.0000000009 -11: 11916 * 360437 -0.0000000009 -10: 9548 * 449829 -0.0000000009 -9: 7620 * 563644 -0.0000000037 -8: 6100 * 704093 0.0000000009 -7: 4904 * 875809 0.0000000093 -6: 3906 * 1099582 -0.0000000009 -5: 3121 * 1376151 -0.0000000058 -4: 2501 * 1717300 0.0000000009 -3: 1991 * 2157191 -0.0000000035 -2: 1586 * 2708050 0.0000000009 -1: 1277 * 3363326 0.0000000014 0: 1024 * 4194304 0.0000000000 1: 820 * 5237765 0.0000000009 2: 655 * 6557202 0.0000000033 3: 526 * 8165337 -0.0000000079 4: 423 * 10153587 0.0000000012 5: 335 * 12820798 0.0000000079 6: 272 * 15790321 0.0000000037 7: 215 * 19976592 -0.0000000037 8: 172 * 24970740 -0.0000000037 9: 137 * 31350126 -0.0000000079 10: 110 * 39045157 -0.0000000061 11: 87 * 49367440 -0.0000000037 12: 70 * 61356676 0.0000000056 13: 56 * 76695844 -0.0000000075 14: 45 * 95443717 -0.0000000072 15: 36 * 119304647 -0.0000000009 16: 29 * 148102320 -0.0000000037 17: 23 * 186737708 -0.0000000028 18: 18 * 238609294 -0.0000000009 19: 15 * 286331153 -0.0000000002 Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+16 −13

Original line number	Diff line number	Diff line
		@@ -704,11 +704,14 @@ static void update_load_sub(struct load_weight *lw, unsigned long dec)
		* the relative distance between them is ~25%.)
		*/
		static const int prio_to_weight[40] = {
		/* -20 */ 88818, 71054, 56843, 45475, 36380, 29104, 23283, 18626, 14901, 11921,
		/* -10 */ 9537, 7629, 6103, 4883, 3906, 3125, 2500, 2000, 1600, 1280,
		/* 0 / NICE_0_LOAD / 1024 */,
		/* 1 */ 819, 655, 524, 419, 336, 268, 215, 172, 137,
		/* 10 */ 110, 87, 70, 56, 45, 36, 29, 23, 18, 15,
		/* -20 */ 88761, 71755, 56483, 46273, 36291,
		/* -15 */ 29154, 23254, 18705, 14949, 11916,
		/* -10 */ 9548, 7620, 6100, 4904, 3906,
		/* -5 */ 3121, 2501, 1991, 1586, 1277,
		/* 0 */ 1024, 820, 655, 526, 423,
		/* 5 */ 335, 272, 215, 172, 137,
		/* 10 */ 110, 87, 70, 56, 45,
		/* 15 */ 36, 29, 23, 18, 15,
		};

		/*
		@@ -719,13 +722,13 @@ static const int prio_to_weight[40] = {
		* into multiplications:
		*/
		static const u32 prio_to_wmult[40] = {
		/* -20 */ 48356, 60446, 75558, 94446, 118058,
		/* -15 */ 147573, 184467, 230589, 288233, 360285,
		/* -10 */ 450347, 562979, 703746, 879575, 1099582,
		/* -5 */ 1374389, 1717986, 2147483, 2684354, 3355443,
		/* 0 */ 4194304, 5244160, 6557201, 8196502, 10250518,
		/* 5 */ 12782640, 16025997, 19976592, 24970740, 31350126,
		/* 10 */ 39045157, 49367440, 61356675, 76695844, 95443717,
		/* -20 */ 48388, 59856, 76040, 92818, 118348,
		/* -15 */ 147320, 184698, 229616, 287308, 360437,
		/* -10 */ 449829, 563644, 704093, 875809, 1099582,
		/* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
		/* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
		/* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
		/* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
		/* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
		};

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