Here's a simple program to replicate the tackled problem.

100googles.c

#include <stdlib.h>
#include <stdio.h>
#include <curl/curl.h>


int main(int argc, char *argv[]) {
	CURLMcode mrc;
	CURLM *multi = NULL;
	CURL *easy[100] = {NULL};
	int i, running, finished;
	FILE *devnull;

	curl_global_init(CURL_GLOBAL_NOTHING);

	devnull = fopen("/dev/null", "w");
	if (!devnull)
	  goto kthxbye;

	multi = curl_multi_init();
	if (!multi)
	  goto kthxbye;

	for (i=0; i<100; ++i) {
	  easy[i] = curl_easy_init();
	  if (!easy[i])
	    goto kthxbye;

	  curl_easy_setopt(easy[i], CURLOPT_WRITEDATA, devnull);
	  curl_easy_setopt(easy[i], CURLOPT_CONNECTTIMEOUT, 30);
	  curl_easy_setopt(easy[i], CURLOPT_TIMEOUT, 30);
	  curl_easy_setopt(easy[i], CURLOPT_URL, "http://www.google.com");
	  curl_multi_add_handle(multi, easy[i]);
	}

	do {
	  CURLMsg *msg;

	  while (CURLM_CALL_MULTI_PERFORM == (mrc = curl_multi_perform(multi, &running)));

	  while ((msg = curl_multi_info_read(multi, &finished))) {
	    long code;

	    if (msg->data.result == CURLE_OK)
	      curl_easy_getinfo(msg->easy_handle, CURLINFO_HTTP_CODE, &code);
	    else
	      code = -((long) msg->data.result);
	    printf("%ld ", code);
	    curl_multi_remove_handle(multi, msg->easy_handle);
	  }
	} while (mrc == CURLM_OK && running > 0);

	kthxbye:
	if (multi)
	  curl_multi_cleanup(multi);

	for (i=0; i<100; ++i)
	  if (easy[i])
	    curl_easy_cleanup(easy[i]);

	curl_global_cleanup();
	exit(0);
}

current.txt

$ time ./100googles
302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 302 302 302 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 -6 ./100googles  12.81s user 2.27s system 100% cpu 15.037 total

fixed.txt

$ time LD_PRELOAD=./lib/.libs/libcurl.so ./100googles
302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 302 LD_PRELOAD=./lib/.libs/libcurl.so ./100googles  0.07s user 0.07s system 119% cpu 0.117 total

The first run with stock libcurl completes in 5 to 15 seconds (probably depending on your resolver setup) and has lots of COULDNT_RESOLVE_HOST or OPERATION_TIMEDOUT result codes.

The fixed version completes in nearly a centisecond.