From: "Michael S. Tsirkin" <mst@redhat.com>
To: Chao Peng <chao.p.peng@linux.intel.com>
Cc: Zha Bin <zhabin@linux.alibaba.com>,
linux-kernel@vger.kernel.org, jasowang@redhat.com,
slp@redhat.com, virtio-dev@lists.oasis-open.org,
qemu-devel@nongnu.org, gerry@linux.alibaba.com,
jing2.liu@linux.intel.com
Subject: Re: [PATCH v2 0/5] virtio mmio specification enhancement
Date: Tue, 11 Feb 2020 05:57:09 -0500 [thread overview]
Message-ID: <20200211053953-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200211160541.GA37446@chaop.bj.intel.com>
On Tue, Feb 11, 2020 at 04:05:41PM +0000, Chao Peng wrote:
> On Mon, Feb 10, 2020 at 06:44:50AM -0500, Michael S. Tsirkin wrote:
> > On Mon, Feb 10, 2020 at 05:05:16PM +0800, Zha Bin wrote:
> > > We have compared the number of files and the lines of code between
> > > virtio-mmio and virio-pci.
> > >
> > > Virtio-PCI Virtio-MMIO
> > > number of files(Linux) 161 1
> > > lines of code(Linux) 78237 538
> >
> >
> >
> > Something's very wrong here. virtio PCI is 161 files?
> > Are you counting the whole PCI subsystem?
>
> Right, that is just a rough statistics.
Please try not to make them look so wrong then.
E.g. you don't include drivers/base/platform-msi.c for
mmio do you? Your patch brings a bunch of code in there.
> Surely enough, some drivers will
> never get enabled in a typcial config.
>
> > Sure enough:
> >
> > $ find drivers/pci -name '*c' |wc -l
> > 150
>
> and plus:
> $ find arch/x86/pci/ -name '*c' |wc -l
> 22
But what's the point? This is code that is maintained by PCI core
people anyway.
> >
> > That's not reasonable, this includes a bunch of drivers that
> > never run on a typical hypervisor.
> >
> > MMIO is also not as small as you are trying to show:
> >
> > $ cloc drivers/virtio/virtio_mmio.c include/uapi/linux/virtio_mmio.h
> > 2 text files.
> > 2 unique files.
> > 0 files ignored.
> >
> > github.com/AlDanial/cloc v 1.82 T=0.01 s (230.7 files/s, 106126.5 lines/s)
> > -------------------------------------------------------------------------------
> > Language files blank comment code
> > -------------------------------------------------------------------------------
> > C 1 144 100 535
> > C/C++ Header 1 39 66 36
> > -------------------------------------------------------------------------------
> > SUM: 2 183 166 571
> > -------------------------------------------------------------------------------
> >
> >
> > I don't doubt MMIO is smaller than PCI. Of course that's because it has
> > no features to speak of - just this patch already doubles it's size. If
> > we keep doing that because we want the features then they will reach
> > the same size in about 4 iterations.
>
> Since current virtio-mmio size is small enough, so adding any notable
> feature would easily double it.
But really unlike PCI this is just PV stuff that is not reused by
anyone. We end up maintaining all this by ourselves.
> I have no objection that it may one day
> reach the same level of PCI, but in this patch some are actually
> generic changes and for MSI specific code we provide the option to
> confige away.
>
> Thanks,
> Chao
The option will make it fall down at runtime but
it does not actually seem to remove all of the overhead.
> >
> >
> > --
> > MST
next prev parent reply other threads:[~2020-02-11 10:57 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-10 9:05 [PATCH v2 0/5] virtio mmio specification enhancement Zha Bin
2020-02-10 9:05 ` [PATCH v2 1/5] virtio-mmio: add notify feature for per-queue Zha Bin
2020-02-11 10:50 ` Michael S. Tsirkin
2020-02-11 11:33 ` Michael S. Tsirkin
2020-02-12 3:39 ` Jason Wang
2020-02-12 8:18 ` Michael S. Tsirkin
2020-02-12 8:53 ` Jason Wang
2020-02-12 9:33 ` Jason Wang
2020-02-12 9:55 ` Michael S. Tsirkin
2020-02-13 3:38 ` Jason Wang
2020-02-10 9:05 ` [PATCH v2 2/5] virtio-mmio: refactor common functionality Zha Bin
2020-02-11 11:19 ` Michael S. Tsirkin
2020-02-12 2:58 ` [virtio-dev] " Liu, Jing2
2020-02-12 7:29 ` Michael S. Tsirkin
2020-02-10 9:05 ` [PATCH v2 3/5] virtio-mmio: create a generic MSI irq domain Zha Bin
2020-02-11 11:16 ` Michael S. Tsirkin
2020-02-12 7:40 ` Michael S. Tsirkin
2020-02-10 9:05 ` [PATCH v2 4/5] virtio-mmio: add MSI interrupt feature support Zha Bin
2020-02-11 3:17 ` Jason Wang
2020-02-11 3:35 ` [virtio-dev] " Liu, Jing2
2020-02-11 4:02 ` Jason Wang
[not found] ` <5522f205-207b-b012-6631-3cc77dde3bfe@linux.intel.com>
2020-02-11 7:40 ` Jason Wang
2020-02-11 11:58 ` Michael S. Tsirkin
2020-02-11 12:04 ` Jason Wang
2020-02-11 12:08 ` Michael S. Tsirkin
2020-02-11 12:18 ` Jason Wang
2020-02-11 14:00 ` Michael S. Tsirkin
2020-02-12 9:03 ` Jason Wang
2020-02-12 9:15 ` Michael S. Tsirkin
[not found] ` <4c19292f-9d25-a859-3dde-6dd5a03fdf0b@linux.intel.com>
2020-02-12 7:33 ` Michael S. Tsirkin
2020-02-12 9:06 ` Jason Wang
2020-02-12 9:16 ` Michael S. Tsirkin
2020-02-13 3:40 ` Jason Wang
2020-02-11 11:21 ` Michael S. Tsirkin
2020-02-11 11:11 ` Michael S. Tsirkin
2020-02-10 9:05 ` [PATCH v2 5/5] x86: virtio-mmio: support virtio-mmio with MSI for x86 Zha Bin
2020-02-11 11:14 ` Michael S. Tsirkin
2020-02-10 11:44 ` [PATCH v2 0/5] virtio mmio specification enhancement Michael S. Tsirkin
2020-02-11 16:05 ` Chao Peng
2020-02-11 10:57 ` Michael S. Tsirkin [this message]
[not found] <DM6PR11MB4331B490586462DE7353E0B8F9710@DM6PR11MB4331.namprd11.prod.outlook.com>
2020-07-31 10:13 ` Stefan Hajnoczi
2020-07-31 15:44 ` Alex Bennée
2020-08-03 16:19 ` Alex Bennée
2020-08-03 23:31 ` Pincus, Josh
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