On Wed, 27 Mar 2002, Jacky Lam wrote:

> I have a program using libcurl to download web pages and related images.
> The program will spawn a number of threads. Each thread will call
> curl_easy_init(), curl_easy_perform() ,curl_easy_cleanup() independently.
> (Is it good?)

Yes, that's fine...

> Can I download more than 1 object with the same handle in one thread?
> (someone is working on that now?)

Yes, you *should* re-use the handle within the same thread as much as
possible, as that'll increase performance, due to persistant connections and
handle-oriented caches.

> Also, I find that each thread will try to resolve the same host name.
> Is there any DNS caching in libcurl?

Yes, but it is per handle only, as there's no support for mutexes in libcurl.
You can force the DNS cache to be used globally, but that will only work if
you fire off once libcurl thread at a time. Again, since there are no mutex
support...

Sharing data and adding mutex support is being discussed and I welcome
everyone to contribute to the discussion and join the effort.

> Actually, I am using libcurl to replace libwww. When the network
> bandwidth is enough, download speed of multi-threaded libcurl is impressive
> (doubly faster than libwww, even not tuned).

This is really suprising. How can that be?

> But when the network is congested, libcurl is serveral times slower than
> libwww. I will happy to work on that if someone has any idea.

This is equally surprising and of course of more concern for us.

I don't have any answers to why this happens. Before we continue on this, can
you please post more detailed and specific, both test results and details on
how your tests have been performed?

Did anyone else notice any symthoms like this?

Then, we should do some careful ethereal'ing or something, to track down
network packet flows and see if they look weird.

Of course we should also dig into the code and see if we're doing something
utterly silly in there. I really can't think of what we can possibly do to
make it not handle congested situations fine. We do the same for all
conditions.

I trust you've done these tests using libcurl 7.9.5?

-- 
    Daniel Stenberg -- curl groks URLs -- http://curl.haxx.se/