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
