1
2
3
4
5
6#include <linux/module.h>
7#include <linux/types.h>
8#include <linux/ctype.h>
9#include <linux/kernel.h>
10#include <linux/jiffies.h>
11#include <linux/dynamic_queue_limits.h>
12
13#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
14#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)
15
16
17void dql_completed(struct dql *dql, unsigned int count)
18{
19 unsigned int inprogress, prev_inprogress, limit;
20 unsigned int ovlimit, completed, num_queued;
21 bool all_prev_completed;
22
23 num_queued = ACCESS_ONCE(dql->num_queued);
24
25
26 BUG_ON(count > num_queued - dql->num_completed);
27
28 completed = dql->num_completed + count;
29 limit = dql->limit;
30 ovlimit = POSDIFF(num_queued - dql->num_completed, limit);
31 inprogress = num_queued - completed;
32 prev_inprogress = dql->prev_num_queued - dql->num_completed;
33 all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);
34
35 if ((ovlimit && !inprogress) ||
36 (dql->prev_ovlimit && all_prev_completed)) {
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52 limit += POSDIFF(completed, dql->prev_num_queued) +
53 dql->prev_ovlimit;
54 dql->slack_start_time = jiffies;
55 dql->lowest_slack = UINT_MAX;
56 } else if (inprogress && prev_inprogress && !all_prev_completed) {
57
58
59
60
61
62
63
64
65
66
67
68 unsigned int slack, slack_last_objs;
69
70
71
72
73
74
75
76
77
78
79
80
81 slack = POSDIFF(limit + dql->prev_ovlimit,
82 2 * (completed - dql->num_completed));
83 slack_last_objs = dql->prev_ovlimit ?
84 POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0;
85
86 slack = max(slack, slack_last_objs);
87
88 if (slack < dql->lowest_slack)
89 dql->lowest_slack = slack;
90
91 if (time_after(jiffies,
92 dql->slack_start_time + dql->slack_hold_time)) {
93 limit = POSDIFF(limit, dql->lowest_slack);
94 dql->slack_start_time = jiffies;
95 dql->lowest_slack = UINT_MAX;
96 }
97 }
98
99
100 limit = clamp(limit, dql->min_limit, dql->max_limit);
101
102 if (limit != dql->limit) {
103 dql->limit = limit;
104 ovlimit = 0;
105 }
106
107 dql->adj_limit = limit + completed;
108 dql->prev_ovlimit = ovlimit;
109 dql->prev_last_obj_cnt = dql->last_obj_cnt;
110 dql->num_completed = completed;
111 dql->prev_num_queued = num_queued;
112}
113EXPORT_SYMBOL(dql_completed);
114
115void dql_reset(struct dql *dql)
116{
117
118 dql->limit = 0;
119 dql->num_queued = 0;
120 dql->num_completed = 0;
121 dql->last_obj_cnt = 0;
122 dql->prev_num_queued = 0;
123 dql->prev_last_obj_cnt = 0;
124 dql->prev_ovlimit = 0;
125 dql->lowest_slack = UINT_MAX;
126 dql->slack_start_time = jiffies;
127}
128EXPORT_SYMBOL(dql_reset);
129
130int dql_init(struct dql *dql, unsigned hold_time)
131{
132 dql->max_limit = DQL_MAX_LIMIT;
133 dql->min_limit = 0;
134 dql->slack_hold_time = hold_time;
135 dql_reset(dql);
136 return 0;
137}
138EXPORT_SYMBOL(dql_init);
139