From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49436) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f5oV1-000095-FS for qemu-devel@nongnu.org; Tue, 10 Apr 2018 04:19:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f5oUv-00083w-AI for qemu-devel@nongnu.org; Tue, 10 Apr 2018 04:19:31 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54836 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f5oUv-00083f-3a for qemu-devel@nongnu.org; Tue, 10 Apr 2018 04:19:25 -0400 Date: Tue, 10 Apr 2018 09:19:21 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180410081921.GA5155@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] qom-test on netbsd can be very slow List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: QEMU Developers , Eric Blake , Markus Armbruster 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 :|