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RE: High CPU Usage when using libcurl with c-ares

From: Dorit Mari via curl-library <curl-library_at_cool.haxx.se>
Date: Mon, 22 Jun 2020 10:21:50 +0000

Hi,

We upgraded the version of libcurl we're working with to 7.70.0, and the problem persists.
I'm sorry, but currently I can't produce a small example source code that reproduces the issue.
What do you mean by "resolver socket" and "transfer socket"?
Since the problem happens under heavy load of multiple parallel HTTP requests, I don't think I can't point to a specific "transfer state".

Thanks,
Dorit

-----Original Message-----
From: Daniel Stenberg [mailto:daniel_at_haxx.se]
Sent: Tuesday, June 16, 2020 00:51
To: Dorit Mari via curl-library <curl-library_at_cool.haxx.se>
Cc: Dorit Mari <Dorit.Mari_at_audiocodes.com>
Subject: Re: High CPU Usage when using libcurl with c-ares

On Sun, 14 Jun 2020, Dorit Mari via curl-library wrote:

> I use libcurl version 7.65.3. The OS is Linux. I always use
> CURLOPT_RESOLVE

...

> libcurl compiled without this flag (45% vs. 12%).

Wow, that's seem super strange. How on earth can the resolving code - that you don't even use - affect the CPU load of the transfer phase? And to that serious degree!

Does the resolver socket linger around during the transfer for you so that you monitor and "act" on it too, in addition to the transfer socket?

In which transfer states do you see this increased CPU load, do you know?

Can you show us a small example source code that reproduces the load issue for you?

> Is there any such known problem/solution?

Not that I can think of. It is of course always clever to build with the latest version as a test shot and see if it makes anything different, it
*might* save us from debugging and chasing ghosts. 

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Received on 2020-06-22