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Release 4.18 lib/dynamic_queue_limits.c

Directory: lib
// SPDX-License-Identifier: GPL-2.0
/*
 * Dynamic byte queue limits.  See include/linux/dynamic_queue_limits.h
 *
 * Copyright (c) 2011, Tom Herbert <therbert@google.com>
 */
#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 execess data queued above * the 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; }

Contributors

PersonTokensPropCommitsCommitProp
Tom Herbert33395.69%125.00%
Hiroaki SHIMODA144.02%250.00%
Mark Rutland10.29%125.00%
Total348100.00%4100.00%

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; }

Contributors

PersonTokensPropCommitsCommitProp
Tom Herbert65100.00%1100.00%
Total65100.00%1100.00%

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); }

Contributors

PersonTokensPropCommitsCommitProp
Tom Herbert3594.59%150.00%
Stephen Hemminger25.41%150.00%
Total37100.00%2100.00%

EXPORT_SYMBOL(dql_init);

Overall Contributors

PersonTokensPropCommitsCommitProp
Tom Herbert47093.25%222.22%
Hiroaki SHIMODA244.76%333.33%
Rasmus Villemoes61.19%111.11%
Stephen Hemminger20.40%111.11%
Greg Kroah-Hartman10.20%111.11%
Mark Rutland10.20%111.11%
Total504100.00%9100.00%
Directory: lib
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