Merge branch 'stable/autoballoon.v5.2' into stable/for-linus-3.5
[platform/adaptation/renesas_rcar/renesas_kernel.git] / lib / dynamic_queue_limits.c
1 /*
2  * Dynamic byte queue limits.  See include/linux/dynamic_queue_limits.h
3  *
4  * Copyright (c) 2011, Tom Herbert <therbert@google.com>
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) ((A) > (B) ? (A) - (B) : 0)
14
15 /* Records completed count and recalculates the queue limit */
16 void dql_completed(struct dql *dql, unsigned int count)
17 {
18         unsigned int inprogress, prev_inprogress, limit;
19         unsigned int ovlimit, all_prev_completed, completed;
20
21         /* Can't complete more than what's in queue */
22         BUG_ON(count > dql->num_queued - dql->num_completed);
23
24         completed = dql->num_completed + count;
25         limit = dql->limit;
26         ovlimit = POSDIFF(dql->num_queued - dql->num_completed, limit);
27         inprogress = dql->num_queued - completed;
28         prev_inprogress = dql->prev_num_queued - dql->num_completed;
29         all_prev_completed = POSDIFF(completed, dql->prev_num_queued);
30
31         if ((ovlimit && !inprogress) ||
32             (dql->prev_ovlimit && all_prev_completed)) {
33                 /*
34                  * Queue considered starved if:
35                  *   - The queue was over-limit in the last interval,
36                  *     and there is no more data in the queue.
37                  *  OR
38                  *   - The queue was over-limit in the previous interval and
39                  *     when enqueuing it was possible that all queued data
40                  *     had been consumed.  This covers the case when queue
41                  *     may have becomes starved between completion processing
42                  *     running and next time enqueue was scheduled.
43                  *
44                  *     When queue is starved increase the limit by the amount
45                  *     of bytes both sent and completed in the last interval,
46                  *     plus any previous over-limit.
47                  */
48                 limit += POSDIFF(completed, dql->prev_num_queued) +
49                      dql->prev_ovlimit;
50                 dql->slack_start_time = jiffies;
51                 dql->lowest_slack = UINT_MAX;
52         } else if (inprogress && prev_inprogress && !all_prev_completed) {
53                 /*
54                  * Queue was not starved, check if the limit can be decreased.
55                  * A decrease is only considered if the queue has been busy in
56                  * the whole interval (the check above).
57                  *
58                  * If there is slack, the amount of execess data queued above
59                  * the the amount needed to prevent starvation, the queue limit
60                  * can be decreased.  To avoid hysteresis we consider the
61                  * minimum amount of slack found over several iterations of the
62                  * completion routine.
63                  */
64                 unsigned int slack, slack_last_objs;
65
66                 /*
67                  * Slack is the maximum of
68                  *   - The queue limit plus previous over-limit minus twice
69                  *     the number of objects completed.  Note that two times
70                  *     number of completed bytes is a basis for an upper bound
71                  *     of the limit.
72                  *   - Portion of objects in the last queuing operation that
73                  *     was not part of non-zero previous over-limit.  That is
74                  *     "round down" by non-overlimit portion of the last
75                  *     queueing operation.
76                  */
77                 slack = POSDIFF(limit + dql->prev_ovlimit,
78                     2 * (completed - dql->num_completed));
79                 slack_last_objs = dql->prev_ovlimit ?
80                     POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0;
81
82                 slack = max(slack, slack_last_objs);
83
84                 if (slack < dql->lowest_slack)
85                         dql->lowest_slack = slack;
86
87                 if (time_after(jiffies,
88                                dql->slack_start_time + dql->slack_hold_time)) {
89                         limit = POSDIFF(limit, dql->lowest_slack);
90                         dql->slack_start_time = jiffies;
91                         dql->lowest_slack = UINT_MAX;
92                 }
93         }
94
95         /* Enforce bounds on limit */
96         limit = clamp(limit, dql->min_limit, dql->max_limit);
97
98         if (limit != dql->limit) {
99                 dql->limit = limit;
100                 ovlimit = 0;
101         }
102
103         dql->adj_limit = limit + completed;
104         dql->prev_ovlimit = ovlimit;
105         dql->prev_last_obj_cnt = dql->last_obj_cnt;
106         dql->num_completed = completed;
107         dql->prev_num_queued = dql->num_queued;
108 }
109 EXPORT_SYMBOL(dql_completed);
110
111 void dql_reset(struct dql *dql)
112 {
113         /* Reset all dynamic values */
114         dql->limit = 0;
115         dql->num_queued = 0;
116         dql->num_completed = 0;
117         dql->last_obj_cnt = 0;
118         dql->prev_num_queued = 0;
119         dql->prev_last_obj_cnt = 0;
120         dql->prev_ovlimit = 0;
121         dql->lowest_slack = UINT_MAX;
122         dql->slack_start_time = jiffies;
123 }
124 EXPORT_SYMBOL(dql_reset);
125
126 int dql_init(struct dql *dql, unsigned hold_time)
127 {
128         dql->max_limit = DQL_MAX_LIMIT;
129         dql->min_limit = 0;
130         dql->slack_hold_time = hold_time;
131         dql_reset(dql);
132         return 0;
133 }
134 EXPORT_SYMBOL(dql_init);