Change #252345

Comments

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

Changed files

• docs/Makefile.am
• docs/internals/TIME-KEEPING.md
• lib/asyn-ares.c
• lib/asyn-thrdd.c
• lib/cf-h1-proxy.c
• lib/cf-h2-proxy.c
• lib/cf-https-connect.c
• lib/cf-ip-happy.c
• lib/cf-socket.c
• lib/cfilters.c
• lib/conncache.c
• lib/conncache.h
• lib/connect.c
• lib/connect.h
• lib/cshutdn.c
• lib/curl_trc.c
• lib/doh.c
• lib/easy.c
• lib/file.c
• lib/ftp.c
• lib/gopher.c
• lib/hostip.c
• lib/http.c
• lib/http2.c
• lib/imap.c
• lib/mqtt.c
• lib/multi.c
• lib/multi_ev.c
• lib/multi_ev.h
• lib/multiif.h
• lib/pingpong.c
• lib/pingpong.h
• lib/pop3.c
• lib/progress.c
• lib/progress.h
• lib/ratelimit.c
• lib/ratelimit.h
• lib/request.c
• lib/sendf.c
• lib/setopt.c
• lib/smb.c
• lib/smtp.c
• lib/socks.c
• lib/telnet.c
• lib/tftp.c
• lib/transfer.c
• lib/transfer.h
• lib/url.c
• lib/url.h
• lib/urldata.h
• lib/vquic/curl_ngtcp2.c
• lib/vquic/curl_osslq.c
• lib/vquic/curl_quiche.c
• lib/vquic/vquic.c
• lib/vquic/vquic_int.h
• lib/vssh/libssh.c
• lib/vssh/libssh2.c
• lib/vtls/gtls.c
• lib/vtls/openssl.c
• lib/vtls/schannel.c
• lib/vtls/vtls.c
• lib/vtls/wolfssl.c
• lib/ws.c
• tests/data/test2500
• tests/unit/unit1303.c
• tests/unit/unit1399.c
• tests/unit/unit3216.c