Branch data Line data Source code
1 : : /*
2 : : * Floating proportions with flexible aging period
3 : : *
4 : : * Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz>
5 : : *
6 : : * The goal of this code is: Given different types of event, measure proportion
7 : : * of each type of event over time. The proportions are measured with
8 : : * exponentially decaying history to give smooth transitions. A formula
9 : : * expressing proportion of event of type 'j' is:
10 : : *
11 : : * p_{j} = (\Sum_{i>=0} x_{i,j}/2^{i+1})/(\Sum_{i>=0} x_i/2^{i+1})
12 : : *
13 : : * Where x_{i,j} is j's number of events in i-th last time period and x_i is
14 : : * total number of events in i-th last time period.
15 : : *
16 : : * Note that p_{j}'s are normalised, i.e.
17 : : *
18 : : * \Sum_{j} p_{j} = 1,
19 : : *
20 : : * This formula can be straightforwardly computed by maintaing denominator
21 : : * (let's call it 'd') and for each event type its numerator (let's call it
22 : : * 'n_j'). When an event of type 'j' happens, we simply need to do:
23 : : * n_j++; d++;
24 : : *
25 : : * When a new period is declared, we could do:
26 : : * d /= 2
27 : : * for each j
28 : : * n_j /= 2
29 : : *
30 : : * To avoid iteration over all event types, we instead shift numerator of event
31 : : * j lazily when someone asks for a proportion of event j or when event j
32 : : * occurs. This can bit trivially implemented by remembering last period in
33 : : * which something happened with proportion of type j.
34 : : */
35 : : #include <linux/flex_proportions.h>
36 : :
37 : 0 : int fprop_global_init(struct fprop_global *p)
38 : : {
39 : : int err;
40 : :
41 : 0 : p->period = 0;
42 : : /* Use 1 to avoid dealing with periods with 0 events... */
43 : 0 : err = percpu_counter_init(&p->events, 1);
44 [ # # ]: 0 : if (err)
45 : : return err;
46 : : seqcount_init(&p->sequence);
47 : 0 : return 0;
48 : : }
49 : :
50 : 0 : void fprop_global_destroy(struct fprop_global *p)
51 : : {
52 : 0 : percpu_counter_destroy(&p->events);
53 : 0 : }
54 : :
55 : : /*
56 : : * Declare @periods new periods. It is upto the caller to make sure period
57 : : * transitions cannot happen in parallel.
58 : : *
59 : : * The function returns true if the proportions are still defined and false
60 : : * if aging zeroed out all events. This can be used to detect whether declaring
61 : : * further periods has any effect.
62 : : */
63 : 0 : bool fprop_new_period(struct fprop_global *p, int periods)
64 : : {
65 : : s64 events;
66 : : unsigned long flags;
67 : :
68 : : local_irq_save(flags);
69 : 3260 : events = percpu_counter_sum(&p->events);
70 : : /*
71 : : * Don't do anything if there are no events.
72 : : */
73 [ + + ]: 3260 : if (events <= 1) {
74 [ - + ]: 200 : local_irq_restore(flags);
75 : : return false;
76 : : }
77 : : write_seqcount_begin(&p->sequence);
78 [ + - ]: 3060 : if (periods < 64)
79 : 3060 : events -= events >> periods;
80 : : /* Use addition to avoid losing events happening between sum and set */
81 : 3060 : percpu_counter_add(&p->events, -events);
82 : 3060 : p->period += periods;
83 : : write_seqcount_end(&p->sequence);
84 [ - + ]: 3060 : local_irq_restore(flags);
85 : :
86 : : return true;
87 : : }
88 : :
89 : : /*
90 : : * ---- SINGLE ----
91 : : */
92 : :
93 : 0 : int fprop_local_init_single(struct fprop_local_single *pl)
94 : : {
95 : 0 : pl->events = 0;
96 : 0 : pl->period = 0;
97 : 0 : raw_spin_lock_init(&pl->lock);
98 : 0 : return 0;
99 : : }
100 : :
101 : 0 : void fprop_local_destroy_single(struct fprop_local_single *pl)
102 : : {
103 : 0 : }
104 : :
105 : 0 : static void fprop_reflect_period_single(struct fprop_global *p,
106 : : struct fprop_local_single *pl)
107 : : {
108 : 0 : unsigned int period = p->period;
109 : : unsigned long flags;
110 : :
111 : : /* Fast path - period didn't change */
112 [ # # ]: 0 : if (pl->period == period)
113 : : return;
114 : 0 : raw_spin_lock_irqsave(&pl->lock, flags);
115 : : /* Someone updated pl->period while we were spinning? */
116 [ # # ]: 0 : if (pl->period >= period) {
117 : 0 : raw_spin_unlock_irqrestore(&pl->lock, flags);
118 : : return;
119 : : }
120 : : /* Aging zeroed our fraction? */
121 [ # # ]: 0 : if (period - pl->period < BITS_PER_LONG)
122 : 0 : pl->events >>= period - pl->period;
123 : : else
124 : 0 : pl->events = 0;
125 : 0 : pl->period = period;
126 : 0 : raw_spin_unlock_irqrestore(&pl->lock, flags);
127 : : }
128 : :
129 : : /* Event of type pl happened */
130 : 0 : void __fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl)
131 : : {
132 : 0 : fprop_reflect_period_single(p, pl);
133 : 0 : pl->events++;
134 : 0 : percpu_counter_add(&p->events, 1);
135 : 0 : }
136 : :
137 : : /* Return fraction of events of type pl */
138 : 0 : void fprop_fraction_single(struct fprop_global *p,
139 : : struct fprop_local_single *pl,
140 : : unsigned long *numerator, unsigned long *denominator)
141 : : {
142 : : unsigned int seq;
143 : : s64 num, den;
144 : :
145 : : do {
146 : : seq = read_seqcount_begin(&p->sequence);
147 : 0 : fprop_reflect_period_single(p, pl);
148 : 0 : num = pl->events;
149 : 0 : den = percpu_counter_read_positive(&p->events);
150 [ # # ]: 0 : } while (read_seqcount_retry(&p->sequence, seq));
151 : :
152 : : /*
153 : : * Make fraction <= 1 and denominator > 0 even in presence of percpu
154 : : * counter errors
155 : : */
156 [ # # ]: 0 : if (den <= num) {
157 [ # # ]: 0 : if (num)
158 : : den = num;
159 : : else
160 : : den = 1;
161 : : }
162 : 0 : *denominator = den;
163 : 0 : *numerator = num;
164 : 0 : }
165 : :
166 : : /*
167 : : * ---- PERCPU ----
168 : : */
169 : : #define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
170 : :
171 : 0 : int fprop_local_init_percpu(struct fprop_local_percpu *pl)
172 : : {
173 : : int err;
174 : :
175 : 0 : err = percpu_counter_init(&pl->events, 0);
176 [ # # ]: 0 : if (err)
177 : : return err;
178 : 0 : pl->period = 0;
179 : 0 : raw_spin_lock_init(&pl->lock);
180 : 0 : return 0;
181 : : }
182 : :
183 : 0 : void fprop_local_destroy_percpu(struct fprop_local_percpu *pl)
184 : : {
185 : 0 : percpu_counter_destroy(&pl->events);
186 : 0 : }
187 : :
188 : 0 : static void fprop_reflect_period_percpu(struct fprop_global *p,
189 : : struct fprop_local_percpu *pl)
190 : : {
191 : 997642 : unsigned int period = p->period;
192 : : unsigned long flags;
193 : :
194 : : /* Fast path - period didn't change */
195 [ + + ]: 997642 : if (pl->period == period)
196 : : return;
197 : 2582 : raw_spin_lock_irqsave(&pl->lock, flags);
198 : : /* Someone updated pl->period while we were spinning? */
199 [ - + ]: 1000224 : if (pl->period >= period) {
200 : 0 : raw_spin_unlock_irqrestore(&pl->lock, flags);
201 : : return;
202 : : }
203 : : /* Aging zeroed our fraction? */
204 [ + - ]: 2582 : if (period - pl->period < BITS_PER_LONG) {
205 : 2582 : s64 val = percpu_counter_read(&pl->events);
206 : :
207 [ - + ][ # # ]: 5164 : if (val < (nr_cpu_ids * PROP_BATCH))
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ + + ]
208 : 1207 : val = percpu_counter_sum(&pl->events);
209 : :
210 [ - + ]: 5164 : __percpu_counter_add(&pl->events,
211 [ # # ][ # # ]: 0 : -val + (val >> (period-pl->period)), PROP_BATCH);
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ]
212 : : } else
213 : 0 : percpu_counter_set(&pl->events, 0);
214 : 2582 : pl->period = period;
215 : 2582 : raw_spin_unlock_irqrestore(&pl->lock, flags);
216 : : }
217 : :
218 : : /* Event of type pl happened */
219 : 0 : void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl)
220 : : {
221 : 0 : fprop_reflect_period_percpu(p, pl);
222 [ # # ][ # # ]: 0 : __percpu_counter_add(&pl->events, 1, PROP_BATCH);
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
223 : 0 : percpu_counter_add(&p->events, 1);
224 : 0 : }
225 : :
226 : 8991 : void fprop_fraction_percpu(struct fprop_global *p,
227 : : struct fprop_local_percpu *pl,
228 : : unsigned long *numerator, unsigned long *denominator)
229 : : {
230 : : unsigned int seq;
231 : : s64 num, den;
232 : :
233 : : do {
234 : : seq = read_seqcount_begin(&p->sequence);
235 : 8991 : fprop_reflect_period_percpu(p, pl);
236 : 8991 : num = percpu_counter_read_positive(&pl->events);
237 : 8991 : den = percpu_counter_read_positive(&p->events);
238 [ - + ]: 8991 : } while (read_seqcount_retry(&p->sequence, seq));
239 : :
240 : : /*
241 : : * Make fraction <= 1 and denominator > 0 even in presence of percpu
242 : : * counter errors
243 : : */
244 [ + + ]: 8991 : if (den <= num) {
245 [ + + ]: 7975 : if (num)
246 : : den = num;
247 : : else
248 : : den = 1;
249 : : }
250 : 8991 : *denominator = den;
251 : 8991 : *numerator = num;
252 : 8991 : }
253 : :
254 : : /*
255 : : * Like __fprop_inc_percpu() except that event is counted only if the given
256 : : * type has fraction smaller than @max_frac/FPROP_FRAC_BASE
257 : : */
258 : 0 : void __fprop_inc_percpu_max(struct fprop_global *p,
259 : : struct fprop_local_percpu *pl, int max_frac)
260 : : {
261 [ - + ]: 988652 : if (unlikely(max_frac < FPROP_FRAC_BASE)) {
262 : : unsigned long numerator, denominator;
263 : :
264 : 0 : fprop_fraction_percpu(p, pl, &numerator, &denominator);
265 [ # # ]: 0 : if (numerator >
266 : 0 : (((u64)denominator) * max_frac) >> FPROP_FRAC_SHIFT)
267 : 0 : return;
268 : : } else
269 : 988652 : fprop_reflect_period_percpu(p, pl);
270 [ + + ][ - + ]: 2965956 : __percpu_counter_add(&pl->events, 1, PROP_BATCH);
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ + - ]
[ + - ][ - - ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
[ # # ][ # # ]
271 : 988652 : percpu_counter_add(&p->events, 1);
272 : : }
|
