On Mon, Apr 09, 2018 at 06:10:43PM +0100, Peter Maydell wrote: > My NetBSD build system recently seems to have taken a nosedive > in how long it takes to finish "make check". This seems to be > because qom-test (and probably other things where the test interacts > with the QEMU process) can run very slowly. > > netbsdvm# for i in 1 2 3 4 5 6 7 8 9 10; do > (QTEST_QEMU_BINARY=x86_64-softmmu/qemu-system-x86_64 time > tests/qom-test -p /x86_64/qom/pc-i440fx-2.0); done > /x86_64/qom/pc-i440fx-2.0: OK > 8.49 real 1.18 user 7.34 sys > /x86_64/qom/pc-i440fx-2.0: OK > 10.41 real 1.32 user 9.09 sys > /x86_64/qom/pc-i440fx-2.0: OK > 8.45 real 1.24 user 7.24 sys > /x86_64/qom/pc-i440fx-2.0: OK > 9.88 real 1.10 user 8.31 sys > /x86_64/qom/pc-i440fx-2.0: OK > 11.60 real 1.47 user 9.90 sys > /x86_64/qom/pc-i440fx-2.0: OK > 10.94 real 1.28 user 9.68 sys > /x86_64/qom/pc-i440fx-2.0: OK > 10.06 real 1.32 user 8.76 sys > /x86_64/qom/pc-i440fx-2.0: OK > 13.38 real 1.37 user 12.04 sys > /x86_64/qom/pc-i440fx-2.0: OK > 16.19 real 1.46 user 14.29 sys > /x86_64/qom/pc-i440fx-2.0: OK > 9.70 real 1.17 user 8.51 sys > > Admittedly this is running in a (KVM) VM, but still, there seems > something wrong with how long each of these is taking. On Linux > each run is less than a second, so there's an order-of-magnitude > slowdown here. Further, I've occasionally seen a run take 100 seconds! > > Does anybody else see this, and any ideas why it might be running slow?
My only real suggestion is to try "git bisect" as presumably this is a regression caused by something we've merged in this dev cycle ? > One thing I noticed looking at ktrace output is that we do > all our reading of QMP input and output with a read syscall > per character. I don't think that's the cause of this slowness, > though. IIRC, that has been long standing behaviour so would be unlikely to explain a recent slowdown, nor the huge variation in time for some runs. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|