Date: Sun, 7 Apr 2013 12:30:38 +0300
From: Gleb Natapov <gleb@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
        Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>,
        Alex Williamson <alex.williamson@redhat.com>,
        Will Deacon <will.deacon@arm.com>,
        Christoffer Dall <c.dall@virtualopensystems.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH RFC] kvm: add PV MMIO EVENTFD
Message-ID: <20130407093038.GL17919@redhat.com>
References: <6D40C5F1-849E-4F32-B391-E1A1BFA8C59D@suse.de>
 <20130404120825.GD17919@redhat.com>
 <959E147D-EB7B-4F4B-9F84-4F1BBA98DEF8@suse.de>
 <20130404123806.GG17919@redhat.com>
 <EF153515-9835-4FB9-B6BC-73D0BDC86492@suse.de>
 <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>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20130404131457.GJ17919@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1461
Lines: 38

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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/