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/*
* Dynamic byte queue limits. See include/linux/dynamic_queue_limits.h
*
* Copyright (c) 2011, Tom Herbert <therbert@google.com>
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/ctype.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/dynamic_queue_limits.h>
#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)
void dql_completed(struct dql *dql, unsigned int count)
{
unsigned int inprogress, prev_inprogress, limit;
unsigned int ovlimit, completed, num_queued;
bool all_prev_completed;
num_queued = ACCESS_ONCE(dql->num_queued);
BUG_ON(count > num_queued - dql->num_completed);
completed = dql->num_completed + count;
limit = dql->limit;
ovlimit = POSDIFF(num_queued - dql->num_completed, limit);
inprogress = num_queued - completed;
prev_inprogress = dql->prev_num_queued - dql->num_completed;
all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);
if ((ovlimit && !inprogress) ||
(dql->prev_ovlimit && all_prev_completed)) {
limit += POSDIFF(completed, dql->prev_num_queued) +
dql->prev_ovlimit;
dql->slack_start_time = jiffies;
dql->lowest_slack = UINT_MAX;
} else if (inprogress && prev_inprogress && !all_prev_completed) {
unsigned int slack, slack_last_objs;
slack = POSDIFF(limit + dql->prev_ovlimit,
2 * (completed - dql->num_completed));
slack_last_objs = dql->prev_ovlimit ?
POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0;
slack = max(slack, slack_last_objs);
if (slack < dql->lowest_slack)
dql->lowest_slack = slack;
if (time_after(jiffies,
dql->slack_start_time + dql->slack_hold_time)) {
limit = POSDIFF(limit, dql->lowest_slack);
dql->slack_start_time = jiffies;
dql->lowest_slack = UINT_MAX;
}
}
limit = clamp(limit, dql->min_limit, dql->max_limit);
if (limit != dql->limit) {
dql->limit = limit;
ovlimit = 0;
}
dql->adj_limit = limit + completed;
dql->prev_ovlimit = ovlimit;
dql->prev_last_obj_cnt = dql->last_obj_cnt;
dql->num_completed = completed;
dql->prev_num_queued = num_queued;
}
EXPORT_SYMBOL(dql_completed);
void dql_reset(struct dql *dql)
{
dql->limit = 0;
dql->num_queued = 0;
dql->num_completed = 0;
dql->last_obj_cnt = 0;
dql->prev_num_queued = 0;
dql->prev_last_obj_cnt = 0;
dql->prev_ovlimit = 0;
dql->lowest_slack = UINT_MAX;
dql->slack_start_time = jiffies;
}
EXPORT_SYMBOL(dql_reset);
int dql_init(struct dql *dql, unsigned hold_time)
{
dql->max_limit = DQL_MAX_LIMIT;
dql->min_limit = 0;
dql->slack_hold_time = hold_time;
dql_reset(dql);
return 0;
}
EXPORT_SYMBOL(dql_init);
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