On Monday 03 December 2007, Markus Hitter wrote: > Am 03.12.2007 um 11:30 schrieb Laurent Vivier: > > But if you think I should remove the buffered case, I can. > > In doubt, less code is always better. For the unlikely case you broke > something badly, there's always the option to take back the patch. > > > BTW, do you think I should enable "cache=off" by default ? > > This would be fine for a transition phase, but likely, the cache=on > case gets forgotten to be removed later. So, do it now.
I think host caching is still useful enough to be enabled by default, and provides a significant performance increase in several cases. - The guest typically has a relatively small quantity of RAM, compared to a modern machine. Allowing the host OS to act as a demand-based L2 cache allows this to be used without having to dedicate excessive quantities of ram to qemu. - I've seen reports that it significantly speeds up the windows installer. - Host cache is persistent between multiple qemu runs. f you're doing anything that requires frequent guest reboots (e.g. kernel debugging) this is going to be a huge win. - You're running a host OS that has limited or no caching (e.g. DOS). I'd hope that the host OS would have cache use heuristics that would help limit cache pollution. Paul