Hi All.

I'm trying to move from easy to multi interface to be able to listen to
other events while curl transfer is in progress.

I use curl_multi_perform, curl_multi_timeout and curl_multi_fdset in the
main loop and curl_multi_perform in callback that is called when there is
an event on CURL fd.

But I encountered one problem:

curl_multi_timeout returned 1 ms
still_running: 1, sleep for 10 ms
curl_multi_perform: main loop
curl_multi_timeout returned 1 ms
still_running: 1, sleep for 10 ms
curl_multi_perform: main loop
curl_multi_timeout returned 200 ms
still_running: 1, sleep for 100 ms
fd 5: read=0, write=1, exception=0, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_multi_perform: main loop
curl_multi_timeout returned 99 ms
still_running: 1, sleep for 100 ms
fd 5: read=0, write=1, exception=0, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
*... about !! 350 !! OF THE SAME CALLS*
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_multi_perform: main loop
curl_multi_timeout returned 119778 ms
still_running: 1, sleep for 100 ms
fd 5: read=1, write=0, exception=0, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_multi_perform: main loop
curl_multi_timeout returned 119678 ms
still_running: 1, sleep for 100 ms
fd 5: read=1, write=0, exception=0, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
curl_cb: curl_multi_perform: callback, curlm=0xf566f0
qh_curl_multi_perform: main loop
still_running: 0

I just need to transfer about 200-300 bytes, so I do not understand why
there are so many callback events. It looks like curl_multi_perform
sometimes do nothing there and as a result I have a busy loop.

Could somebody explain what is happening under the hood and how to avoid
such a busy loop?

Thanks,
Sergey.

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Received on 2016-11-30