On 05/10/2016 09:00, Thomas Huth wrote: > On 04.10.2016 19:16, Paolo Bonzini wrote: >> >> >> On 04/10/2016 16:18, Thomas Huth wrote: >>>>>>> Using only tcg has also some disadvantages: For some tests, it's >>>>>>> interesting to know whether they also work properly with KVM (e.g. >>>>>>> migration tests), and only using tcg by default slows down the "make >>>>>>> check" quite a bit - which might become an issue now that we're adding >>>>>>> more and more tests. >>>>> >>>>> Which tests are you seeing a slow-down for ? >>> Well, everything that is using accel=tcg in tests/ could be accelerated. >>> For example, the new ipv6/ppc64 unit test is quite slow with TCG: >>> >>> sudo QTEST_QEMU_BINARY=ppc64-softmmu/qemu-system-ppc64 time tests/pxe-test >>> >>> 48.46user 0.07system 0:48.48elapsed >> >> Could that point to a firmware bug? 10 network-bound seconds for a boot >> makes some sense, but 10 CPU-bound seconds don't... > > SLOF is incredibly slow with TCG - most parts are written in Forth that > gets interpreted during runtime, and that seems to perform quite badly > with TCG for some reasons. We're in progress of speeding up the boot > process of SLOF a little bit (see > https://github.com/aik/SLOF/commit/b3fde41bc75269df2 for example), but > it will likely always be slower than a firmware that has been written in > C only.
For what it's worth, just adding "-nodefaults -serial mon:stdio -net nic,model=virtio -net user" saves 7 seconds (30%) on the time needed to reach the OpenFirmware prompt. SCSI seems to be the slowest device to scan. Paolo
