Re: [Qemu-devel] [PATCH] curl: fix curl read

[Stefan Hajnoczi <stefanha@redhat.com>]

On Wed, May 15, 2013 at 11:29:29AM +0800, Fam Zheng wrote:
> On Thu, 05/09 17:16, Stefan Hajnoczi wrote:
> > On Thu, May 09, 2013 at 02:56:50PM +0800, Fam Zheng wrote:
> > > On Thu, 05/09 08:41, Stefan Hajnoczi wrote:
> > > > On Fri, May 03, 2013 at 04:00:09PM +0800, Fam Zheng wrote:
> > > > > +    cache = curl_find_cache(s, aio_base, aio_bytes);
> > > > > +    if (cache) {
> > > > > +        curl_complete_io(s, acb, cache);
> > > > > +        return;
> > > > >      }
> > > > 
> > > > What is the point of the cache?  Can you split it into a separate patch?
> > > 
> > > The cache is for prefetch. Data is fetched by 256k chunks using libcurl
> > > and stored in cache to fill future io request, reducing overall http
> > > request overhead.
> > 
> > That sounds like a performance optimization which is not part of fixing
> > broken block/curl.c :).
> > 
> 
> I didn't invent it here. Read ahead is already in curl.c, (see
> BDRVCURLState.readahead_size). I don't think it's time to remove it here
> either, but rename to a better name should be OK. What do you think?

Yes, that's true.  Although I'm not a fan of readahead I guess it's
already implemented.

> BTW please keep me CC'ed when reply so that I can notice it better.

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Stefan