On Friday, March 10, 2017 9:52:07 AM MST Stefan Hajnoczi wrote: > On Fri, Mar 03, 2017 at 10:05:06AM -0700, Thomas Fjellstrom wrote: > > I've been testing a new samsung 960 evo nvme drive i just got, and running > > tests on it in a guest shows a minimum of double the cpu time on the host > > as it does on the guest. Somehow a guest running a single thread iozone > > or fio test can use 4+ cores on the host side at 50-100%. > > Are you using -drive aio=native? Yes. > Are you pinning threads on the host? No pinning by default. > If the answer to both questions is no, then QEMU uses a thread pool for > disk I/O and those threads could be scheduled on any host CPU. But should they be pegging 4 or more cores, when the host can do the same work with a single core? I don't mind it spreading work out. But using 4x the cpu time to do the same work is a bit much. > Stefan -- Thomas Fjellstrom thomas@xxxxxxxxxxxxx
