On Tue, 05/14 10:22, Stefan Hajnoczi wrote: > On Tue, May 14, 2013 at 10:26:19AM +0800, Fam Zheng wrote: > > - CURLDataCache holds the user data read from libcurl, it is in a list > > ordered by access, the used cache is moved to list head on access, so > > the tail element is freed first. BDRVCURLState.cache_quota is the > > threshold to start freeing cache. > > Can you explain the need for a cache? > > The guest kernel already does readahead if it wants to. It can be tuned > from inside the guest if performance doesn't meet expectations. The > block/curl.c-specific cache cannot be tuned from the guest. >
It's prefetch. If we send request for every read request, there'll be too much overhead for protocal transactions. I just name it CURLDataCache. Guest may have multiple sequencial reads, so I used a list of it. If you think this is reasonable, I'll update the commit messages on this. -- Fam
