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Tue, 7 Jul 2020 12:00:12 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 2B7571132FD2; Tue, 7 Jul 2020 14:00:06 +0200 (CEST) From: Markus Armbruster To: Paolo Bonzini Subject: Re: Slow down with: 'Make "info qom-tree" show children sorted' References: <20200527084754.7531-1-armbru@redhat.com> <20200527084754.7531-3-armbru@redhat.com> <49bea110-0a3d-5a40-6647-67b116fb41b5@redhat.com> <5e967e5f-8ae5-01cc-0dfe-f22e0f03b6b3@redhat.com> <87y2nvanya.fsf@dusky.pond.sub.org> <794f6901-5fe3-f7a1-45e7-f277f687cb6b@redhat.com> Date: Tue, 07 Jul 2020 14:00:06 +0200 In-Reply-To: <794f6901-5fe3-f7a1-45e7-f277f687cb6b@redhat.com> (Paolo Bonzini's message of "Tue, 7 Jul 2020 10:00:34 +0200") Message-ID: <87v9iz7cxl.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=207.211.31.120; envelope-from=armbru@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/07 00:46:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laurent Vivier , Thomas Huth , berrange@redhat.com, ehabkost@redhat.com, Alex =?utf-8?Q?Benn=C3=A9e?= , mark.cave-ayland@ilande.co.uk, qemu-devel@nongnu.org, Greg Kurz , =?utf-8?Q?C=C3=A9dric?= Le Goater , David Gibson , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Paolo Bonzini writes: > On 07/07/20 07:33, Markus Armbruster wrote: >> Philippe Mathieu-Daud=C3=A9 writes: >>=20 >>> On 7/7/20 6:45 AM, Thomas Huth wrote: >>>> On 27/05/2020 10.47, Markus Armbruster wrote: >>>>> "info qom-tree" prints children in unstable order. This is a pain >>>>> when diffing output for different versions to find change. Print it >>>>> sorted. >>>>> >>>>> Signed-off-by: Markus Armbruster >>>>> --- >>>>> qom/qom-hmp-cmds.c | 24 ++++++++++++++++-------- >>>>> 1 file changed, 16 insertions(+), 8 deletions(-) >>>> >>>> Hi Markus, >>>> >>>> this patch causes a slow down of the qtests which becomes quite massiv= e >>>> when e.g. using the ppc64 and thourough testing. When I'm running >>>> >>>> QTEST_QEMU_BINARY=3D"ppc64-softmmu/qemu-system-ppc64" time \ >>>> ./tests/qtest/device-introspect-test -m slow | tail -n 10 >>>> >>>> the test runs for ca. 6m40s here before the patch got applied, and for >>>> mor than 20 minutes after the patch got applied! >>=20 >> That's surprising. > > It's a bit surprising indeed, but on the other hand using > g_queue_insert_sorted results in a quadratic loop. The surprising part is that n turns out to be large enough for n^2 to matter *that* much. > It should probably > be fixed by using g_queue_sort, or switching to g_list_prepend+g_list_sor= t. Yes. Additional ideas on how to make the test less wasteful elsewhere in the thread.