mirror of
https://github.com/openvswitch/ovs
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97 lines
2.7 KiB
C
97 lines
2.7 KiB
C
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/*
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* Copyright (c) 2012 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <config.h>
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#include "token-bucket.h"
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#include "poll-loop.h"
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#include "sat-math.h"
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#include "timeval.h"
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#include "util.h"
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/* Initializes 'tb' to accumulate 'rate' tokens per millisecond, with a
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* maximum of 'burst' tokens.
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*
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* The token bucket is initially full.
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*
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* It may be more convenient to use TOKEN_BUCKET_INIT. */
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void
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token_bucket_init(struct token_bucket *tb,
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unsigned int rate, unsigned int burst)
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{
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tb->rate = rate;
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tb->burst = burst;
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tb->tokens = 0;
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tb->last_fill = LLONG_MIN;
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}
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/* Changes 'tb' to accumulate 'rate' tokens per millisecond, with a maximum of
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* 'burst' tokens.
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*
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* 'tb' must already have been initialized with TOKEN_BUCKET_INIT or
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* token_bucket_init(). */
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void
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token_bucket_set(struct token_bucket *tb,
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unsigned int rate, unsigned int burst)
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{
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tb->rate = rate;
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tb->burst = burst;
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if (burst > tb->tokens) {
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tb->tokens = burst;
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}
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}
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/* Attempts to remove 'n' tokens from 'tb'. Returns true if successful, false
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* if 'tb' contained fewer than 'n' tokens (and thus 'n' tokens could not be
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* removed) . */
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bool
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token_bucket_withdraw(struct token_bucket *tb, unsigned int n)
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{
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if (tb->tokens < n) {
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long long int now = time_msec();
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if (now > tb->last_fill) {
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unsigned long long int elapsed_ull
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= (unsigned long long int) now - tb->last_fill;
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unsigned int elapsed = MIN(UINT_MAX, elapsed_ull);
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unsigned int add = sat_mul(tb->rate, elapsed);
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unsigned int tokens = sat_add(tb->tokens, add);
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tb->tokens = MIN(tokens, tb->burst);
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tb->last_fill = now;
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}
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if (tb->tokens < n) {
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return false;
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}
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}
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tb->tokens -= n;
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return true;
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}
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/* Causes the poll loop to wake up when at least 'n' tokens will be available
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* for withdrawal from 'tb'. */
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void
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token_bucket_wait(struct token_bucket *tb, unsigned int n)
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{
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if (tb->tokens >= n) {
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poll_immediate_wake();
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} else {
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unsigned int need = n - tb->tokens;
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poll_timer_wait_until(tb->last_fill + need / tb->rate + 1);
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}
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}
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