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


From: Fam Zheng
Subject: Re: [Qemu-devel] [PATCH] curl: fix curl read
Date: Wed, 15 May 2013 11:29:29 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

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?

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

-- 
Fam



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