On 09/24/2012 08:30 PM, Kevin Wolf wrote: > Am 24.09.2012 13:32, schrieb ching: >> Hi all, >> >> My host is qemu-1.1.1 and x64 kernel 3.5.4. The guest is using aio="native" >> >> I am trying to use unsafe cache mode to boost i/o performance. > aio=native requires the image to be opened with O_DIRECT, i.e. > cache=none or cache=directsync. If you specify a different cache option, > it will silently fall back to aio=threads. > > Kevin >
will qemu log a entry for the silent fallback? Reason: I am testing sparse image on btrfs with mount option: rw,noatime,space_cache,autodefrag,inode_cache i encounter a speed difference (around 2X-3X) between aio=threads,cache=unsafe and aio=native,cache=unsafe aio=threads is much faster, i guest there is conflict between "autodefrag" and linux aio ching
