From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH RFC] kvm: add PV MMIO EVENTFD Date: Sun, 7 Apr 2013 11:43:01 +0300 Message-ID: <20130407084301.GC10317@redhat.com> References: <20130404120825.GD17919@redhat.com> <959E147D-EB7B-4F4B-9F84-4F1BBA98DEF8@suse.de> <20130404123806.GG17919@redhat.com> <20130404124501.GH17919@redhat.com> <1B68D701-103D-4B1A-8F5E-3916753699CB@suse.de> <20130404125649.GI17919@redhat.com> <8E65D34D-2DA7-4C2E-9C3E-BE3A7DBC3279@suse.de> <20130404131457.GJ17919@redhat.com> <20130407093038.GL17919@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20130407093038.GL17919@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Gleb Natapov Cc: Andrew Morton , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Will Deacon , Xiao Guangrong , Ingo Molnar , "H. Peter Anvin" , Sasha Levin , Thomas Gleixner , Christoffer Dall , virtualization@lists.linux-foundation.org, Takuya Yoshikawa List-Id: virtualization@lists.linuxfoundation.org On Sun, Apr 07, 2013 at 12:30:38PM +0300, Gleb Natapov wrote: > On Thu, Apr 04, 2013 at 04:14:57PM +0300, Gleb Natapov wrote: > > > > > > > >>> is to move to MMIO only when PIO address space is exhausted. For PCI it > > > >>> will be never, for PCI-e it will be after ~16 devices. > > > >> > > > >> Ok, let's go back a step here. Are you actually able to measure any speed in performance with this patch applied and without when going through MMIO kicks? > > > >> > > > >> > > > > That's the question for MST. I think he did only micro benchmarks till > > > > now and he already posted his result here: > > > > > > > > mmio-wildcard-eventfd:pci-mem 3529 > > > > mmio-pv-eventfd:pci-mem 1878 > > > > portio-wildcard-eventfd:pci-io 1846 > > > > > > > > So the patch speedup mmio by almost 100% and it is almost the same as PIO. > > > > > > Those numbers don't align at all with what I measured. > > I am trying to run vmexit test on AMD now, but something does not work > > there. Next week I'll fix it and see how AMD differs, bit on Intel those are the > > numbers. > > > The numbers are: > vmcall 1921 > inl_from_kernel 4227 > outl_to_kernel 2345 > > outl is specifically optimized to not go through the emulator since it > is used for virtio kick. mmio-pv-eventfd is the same kind of > optimization but for mmio. > > -- > Gleb. Hmm so on AMD it's more like 20% overhead, like ARM. -- MST