forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
138 lines
4.3 KiB
138 lines
4.3 KiB
// SPDX-License-Identifier: GPL-2.0 |
|
/* |
|
* Dynamic byte queue limits. See include/linux/dynamic_queue_limits.h |
|
* |
|
* Copyright (c) 2011, Tom Herbert <[email protected]> |
|
*/ |
|
#include <linux/types.h> |
|
#include <linux/kernel.h> |
|
#include <linux/jiffies.h> |
|
#include <linux/dynamic_queue_limits.h> |
|
#include <linux/compiler.h> |
|
#include <linux/export.h> |
|
|
|
#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0) |
|
#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0) |
|
|
|
/* Records completed count and recalculates the queue limit */ |
|
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 = READ_ONCE(dql->num_queued); |
|
|
|
/* Can't complete more than what's in queue */ |
|
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)) { |
|
/* |
|
* Queue considered starved if: |
|
* - The queue was over-limit in the last interval, |
|
* and there is no more data in the queue. |
|
* OR |
|
* - The queue was over-limit in the previous interval and |
|
* when enqueuing it was possible that all queued data |
|
* had been consumed. This covers the case when queue |
|
* may have becomes starved between completion processing |
|
* running and next time enqueue was scheduled. |
|
* |
|
* When queue is starved increase the limit by the amount |
|
* of bytes both sent and completed in the last interval, |
|
* plus any previous over-limit. |
|
*/ |
|
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) { |
|
/* |
|
* Queue was not starved, check if the limit can be decreased. |
|
* A decrease is only considered if the queue has been busy in |
|
* the whole interval (the check above). |
|
* |
|
* If there is slack, the amount of excess data queued above |
|
* the amount needed to prevent starvation, the queue limit |
|
* can be decreased. To avoid hysteresis we consider the |
|
* minimum amount of slack found over several iterations of the |
|
* completion routine. |
|
*/ |
|
unsigned int slack, slack_last_objs; |
|
|
|
/* |
|
* Slack is the maximum of |
|
* - The queue limit plus previous over-limit minus twice |
|
* the number of objects completed. Note that two times |
|
* number of completed bytes is a basis for an upper bound |
|
* of the limit. |
|
* - Portion of objects in the last queuing operation that |
|
* was not part of non-zero previous over-limit. That is |
|
* "round down" by non-overlimit portion of the last |
|
* queueing operation. |
|
*/ |
|
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; |
|
} |
|
} |
|
|
|
/* Enforce bounds on limit */ |
|
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) |
|
{ |
|
/* Reset all dynamic values */ |
|
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); |
|
|
|
void dql_init(struct dql *dql, unsigned int hold_time) |
|
{ |
|
dql->max_limit = DQL_MAX_LIMIT; |
|
dql->min_limit = 0; |
|
dql->slack_hold_time = hold_time; |
|
dql_reset(dql); |
|
} |
|
EXPORT_SYMBOL(dql_init);
|
|
|