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High CPU Usage when using libcurl with c-ares

From: Dorit Mari via curl-library <curl-library_at_cool.haxx.se>
Date: Sun, 14 Jun 2020 16:14:35 +0000

Hi,

I encountered a problem of high CPU usage when using libcurl with c-ares option.

I'm using libcurl in a program for sending many HTTP requests in parallel (with a Multi handle). I use libcurl with libev, loosely based on the example in https://curl.haxx.se/libcurl/c/evhiperfifo.html.
I use libcurl version 7.65.3. The OS is Linux.
I always use CURLOPT_RESOLVE option to specify the resolution of the destination host, so libcurl shouldn't be doing any DNS resolutions (and indeed, the only functions in asyn-ares.c that are called are Curl_resolver_init, Curl_resolver_kill, Curl_resolver_cancel, destroy_async_data and Curl_resolver_cleanup).
When libcurl is compiled with flag "--enable-ares", the CPU usage of the relevant thread is much higher than the same code, but with libcurl compiled without this flag (45% vs. 12%).

Is there any such known problem/solution?

Thanks,
Dorit

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Received on 2020-06-14