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Thu, 12 Mar 2020 17:02:24 +0000 (UTC) Received: from work-vm (ovpn-116-106.ams2.redhat.com [10.36.116.106]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 33E8F8FBE1; Thu, 12 Mar 2020 17:02:21 +0000 (UTC) Date: Thu, 12 Mar 2020 17:02:19 +0000 From: "Dr. David Alan Gilbert" To: Eric Blake Subject: Re: [PATCH] migration/throttle: Add throttle-trig-thres migration parameter Message-ID: <20200312170219.GK3211@work-vm> References: <20200221025727.63808-1-zhukeqian1@huawei.com> <2db47b97-729f-4ccb-dab2-585771acc2fe@redhat.com> MIME-Version: 1.0 In-Reply-To: <2db47b97-729f-4ccb-dab2-585771acc2fe@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: Juan Quintela , qemu-devel@nongnu.org, Markus Armbruster , qemu-arm@nongnu.org, wanghaibin.wang@huawei.com, Keqian Zhu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Eric Blake (eblake@redhat.com) wrote: > On 2/20/20 8:57 PM, Keqian Zhu wrote: > > Currently, if the bytes_dirty_period is more than the 50% of > > bytes_xfer_period, we start or increase throttling. > >=20 > > If we make this percentage higher, then we can tolerate higher > > dirty rate during migration, which means less impact on guest. > > The side effect of higher percentage is longer migration time. > >=20 > > We can configure this parameter to switch between migration time > > firt or guest performance first. The default value is 50. > >=20 > > Signed-off-by: Keqian Zhu > > --- > > Cc: Juan Quintela > > Cc: "Dr. David Alan Gilbert" > > Cc: Eric Blake > > Cc: Markus Armbruster > > --- >=20 > > +++ b/qapi/migration.json > > @@ -524,6 +524,10 @@ > > # compression, so set the decompress-threads to = the number about 1/4 > > # of compress-threads is adequate. > > # > > +# @throttle-trig-thres: The ratio of bytes_dirty_period and bytes_xfer= _period to > > +# trigger throttling. It is expressed as percent= age. The > > +# default value is 50. (Since 5.0) > > +# >=20 > Abbreviating feels odd; can you please spell this out as > throttle-trigger-threshold? >=20 > Can the threshold exceed 100%? Note the code checks for that and disallows it, only allowing 1..99 Dave >=20 > --=20 > Eric Blake, Principal Software Engineer > Red Hat, Inc. +1-919-301-3226 > Virtualization: qemu.org | libvirt.org -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK