On 8/12/25 15:59, Christoph Hellwig wrote: > On Tue, Aug 12, 2025 at 03:53:54PM +0800, Chao Yu wrote: >>> What did you use before? At least for older qemu the default was >>> buffered I/O, which can lead to very expensive fua or flush calls. >> >> Previously, I didn't use any cache= option, as manual described, it >> should equal to cache=wrteback. > > Modern qemu actually split the cache option. You absolute want > cache.direct=on. If you don't do simulated power fail testing by Yes, > killing qemu (or run real workloads for the matter, but who does that > :)) it might make sense to just ignore the flushes with cache.no-flush=on Yes, I don't care whether data can be persisted to host devices or not, nor killing qemu for test, so cache.no-flush=on looks good to me as well. > as well, which is what I do for my test VMs on the laptop. Thanks for sharing this, it helps. :) Thanks,
