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2de22a00c7
Use `data->progress.now` as the timestamp of proecssing a transfer. Update it on significant events and refrain from calling `curlx_now()` in many places. The problem this addresses is a) calling curlx_now() has costs, depending on platform. Calling it every time results in 25% increase `./runtest` duration on macOS. b) we used to pass a `struct curltime *` around to save on calls, but when some method directly use `curx_now()` and some use the passed pointer, the transfer experienes non-linear time. This results in timeline checks to report events in the wrong order. By keeping a timestamp in the easy handle and updating it there, no longer invoking `curlx_now()` in the "lower" methods, the transfer can observer a steady clock progression. Add documentation in docs/internals/TIME-KEEPING.md Reported-by: Viktor Szakats Fixes #19935 Closes #19961
92 lines
4 KiB
C
92 lines
4 KiB
C
#ifndef HEADER_Curl_rlimit_H
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#define HEADER_Curl_rlimit_H
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/***************************************************************************
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* _ _ ____ _
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* Project ___| | | | _ \| |
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* / __| | | | |_) | |
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* | (__| |_| | _ <| |___
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* \___|\___/|_| \_\_____|
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*
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* Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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*
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* This software is licensed as described in the file COPYING, which
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* you should have received as part of this distribution. The terms
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* are also available at https://curl.se/docs/copyright.html.
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*
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* You may opt to use, copy, modify, merge, publish, distribute and/or sell
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* copies of the Software, and permit persons to whom the Software is
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* furnished to do so, under the terms of the COPYING file.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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* SPDX-License-Identifier: curl
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*
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***************************************************************************/
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#include "curlx/timeval.h"
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/* This is a rate limiter that provides "tokens" to be consumed
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* per second with a "burst" rate limitation. Example:
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* A rate limit of 1 megabyte per second with a burst rate of 1.5MB.
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* - initially 1 million tokens are available.
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* - these are drained in the first second.
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* - checking available tokens before the 2nd second will return 0.
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* - at/after the 2nd second, 1 million tokens are available again.
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* - nothing happens for a second, the 1 million tokens would grow
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* to 2 million, however the burst limit caps those at 1.5 million.
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* Thus:
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* - setting "burst" to CURL_OFF_T_MAX would average tokens over the
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* complete lifetime. E.g. for a download, at the *end* of it, the
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* average rate from start to finish would be the rate limit.
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* - setting "burst" to the same value as "rate" would make a
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* download always try to stay *at/below* the rate and slow times will
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* not generate extra tokens.
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* A rate limit can be blocked, causing the available tokens to become
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* always 0 until unblocked. After unblocking, the rate limiting starts
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* again with no history of the past.
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* Finally, a rate limiter with rate 0 will always have CURL_OFF_T_MAX
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* tokens available, unless blocked.
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*/
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struct Curl_rlimit {
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curl_off_t rate_per_step; /* rate tokens are generated per step us */
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curl_off_t burst_per_step; /* burst rate of tokens per step us */
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timediff_t step_us; /* microseconds between token increases */
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curl_off_t tokens; /* tokens available in the next second */
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timediff_t spare_us; /* microseconds unaffecting tokens */
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struct curltime ts; /* time of the last update */
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BIT(blocked); /* blocking sets available tokens to 0 */
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};
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void Curl_rlimit_init(struct Curl_rlimit *r,
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curl_off_t rate_per_s,
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curl_off_t burst_per_s,
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struct curltime *pts);
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/* Start ratelimiting with the given timestamp. Resets available tokens. */
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void Curl_rlimit_start(struct Curl_rlimit *r, struct curltime *pts);
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/* How many milliseconds to wait until token are available again. */
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timediff_t Curl_rlimit_wait_ms(struct Curl_rlimit *r,
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struct curltime *pts);
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/* Return if rate limiting of tokens is active */
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bool Curl_rlimit_active(struct Curl_rlimit *r);
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bool Curl_rlimit_is_blocked(struct Curl_rlimit *r);
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/* Return how many tokens are available to spend, may be negative */
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curl_off_t Curl_rlimit_avail(struct Curl_rlimit *r,
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struct curltime *pts);
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/* Drain tokens from the ratelimit, return how many are now available. */
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void Curl_rlimit_drain(struct Curl_rlimit *r,
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size_t tokens,
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struct curltime *pts);
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/* Block/unblock ratelimiting. A blocked ratelimit has 0 tokens available. */
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void Curl_rlimit_block(struct Curl_rlimit *r,
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bool activate,
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struct curltime *pts);
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#endif /* HEADER_Curl_rlimit_H */
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