Re: Large download speed deviations for CURLOPT_MAX_RECV_SPEED_LARGE in 8.4.0

From: Daniel Stenberg via curl-library <curl-library_at_lists.haxx.se>
Date: Fri, 1 Dec 2023 09:37:03 +0100 (CET)

On Fri, 1 Dec 2023, Dmitry Karpov via curl-library wrote:

> I tried the latest master branch with Daniel's fix, and I still see large
> deviations (up to 20%) from the speed limit set by
> CURLOPT_MAX_RECV_SPEED_LARGE. The deviations depend on a network speed and
> they get bigger when the speed limit gets far from the network speed.

I can't reproduce that. I do this to test:

$ curl --limit-rate 5M localhost/100G -o /dev/null

Here's my debug patch to verify the math in Curl_pgrsLimitWaitTime:

diff --git a/lib/progress.c b/lib/progress.c
index e96cbf7af..8473cfc07 100644
--- a/lib/progress.c
+++ b/lib/progress.c
_at__at_ -298,19 +298,26 _at__at_ timediff_t Curl_pgrsLimitWaitTime(curl_off_t cursize,
        minimum *= 1000;
      else
        minimum = TIMEDIFF_T_MAX;
    }

+ fprintf(stderr, "size % " CURL_FORMAT_CURL_OFF_T
+ " limit: %" CURL_FORMAT_CURL_OFF_T
+ " min: %ld\n",
+ size, limit, minimum);
+
    /*
     * 'actual' is the time in milliseconds it took to actually download the
     * last 'size' bytes.
     */
    actual = Curl_timediff_ceil(now, start);
    if(actual < minimum) {
      /* if it downloaded the data faster than the limit, make it wait the
         difference */
- return (minimum - actual);
+ timediff_t delta = (minimum - actual);
+ fprintf(stderr, "took %ldms wait %ldms more\n", actual, delta);
+ return delta;
    }

    return 0;
  }

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Received on 2023-12-01