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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a9a79456a1sm254780785a.22.2024.09.09.14.30.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Sep 2024 14:30:16 -0700 (PDT) Date: Mon, 9 Sep 2024 17:30:14 -0400 From: Peter Xu To: Hyman Huang Cc: qemu-devel@nongnu.org, Fabiano Rosas , Eric Blake , Markus Armbruster , David Hildenbrand , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Paolo Bonzini Subject: Re: [PATCH RESEND RFC 03/10] qapi/migration: Introduce periodic CPU throttling parameters Message-ID: References: <0bbcdfd86f35830e0a398220663aac5afd8b7e1e.1725891841.git.yong.huang@smartx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <0bbcdfd86f35830e0a398220663aac5afd8b7e1e.1725891841.git.yong.huang@smartx.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.141, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Sep 09, 2024 at 10:25:36PM +0800, Hyman Huang wrote: > To activate the periodic CPU throttleing feature, introduce > the cpu-periodic-throttle. > > To control the frequency of throttling, introduce the > cpu-periodic-throttle-interval. > > Signed-off-by: Hyman Huang Considering that I would still suggest postcopy over auto-converge, IMO we should be cautious on adding more QMP interfaces on top of auto-converge, because that means more maintenance burden everywhere.. and it's against our goal to provide, hopefully, one solution for the long term for convergence issues. Postcopy has a major issue with VFIO, but auto converge isn't anything better from that regard.. as we can't yet throttle a device so far anyway. Throttling of DMA probably means DMA faults, then postcopy might be doable too. Meanwhile we're looking at working out 1G postcopy at some point. So I wonder whether we can make any further optmization for auto-converge (if we still really want that..) to be at least transparent, so that they get auto enabled on new machine types. If we really want some knobs to control, we can still expose via -global migration.x-* parameters, but then they'll be all debug tunables only, perhaps that can at least reduce burdens to QMP maintainers and Libvirt side. Thanks, -- Peter Xu