Paul Brook, le Mon 03 Dec 2007 15:39:48 +0000, a écrit : > 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).
Yes, and in other cases (e.g. real-production KVM/Xen servers), this is just cache duplication. > I'd hope that the host OS would have cache use heuristics that would help > limit cache pollution. How could it? It can't detect that the guest also has a buffer/page cache. Samuel
