lib: keep timestamp in easy handle

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
This commit is contained in:
Stefan Eissing 2025-12-15 14:28:09 +01:00 committed by Daniel Stenberg
parent 425a2aa1af
commit 2de22a00c7
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67 changed files with 598 additions and 458 deletions

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@ -87,7 +87,7 @@ CURLcode Curl_pp_statemach(struct Curl_easy *data, struct pingpong *pp,
bool block, bool disconnecting);
/* initialize stuff to prepare for reading a fresh new response */
void Curl_pp_init(struct pingpong *pp);
void Curl_pp_init(struct pingpong *pp, struct curltime *pnow);
/* Returns timeout in ms. 0 or negative number means the timeout has already
triggered */