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From: Chao Peng <chao.p.peng@linux.intel.com>
To: "Michael S. Tsirkin" <mst@redhat.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 16:05:41 +0000	[thread overview]
Message-ID: <20200211160541.GA37446@chaop.bj.intel.com> (raw)
In-Reply-To: <20200210062938-mutt-send-email-mst@kernel.org>

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. 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

> 
> 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. 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

> 
> 
> -- 
> MST

  reply	other threads:[~2020-02-11  9:23 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10  9:05 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 [this message]
2020-02-11 10:57     ` Michael S. Tsirkin
     [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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