On Fri, Jan 10, 2014 at 09:19:37PM -0800, Michael Dalton wrote: > Hi Jason, Michael > > Sorry for the delay in response. Jason, I agree this patch ended up > being larger than expected. The major implementation parts are: > (1) Setup directory structure (driver/per-netdev/rx-queue directories) > (2) Network device renames (optional, so debugfs dir has the right name) > (3) Support resizing the # of RX queues (optional - we could just export > max_queue_pairs files and not delete files if an RX queue is disabled) > (4) Reference counting - used in case someone opens a debugfs > file and then removes the virtio-net device. > (5) The actual mergeable rx buffer file implementation itself. For now > I have added a seqcount for memory safety, but if a read-only race > condition is acceptable we could elide the seqcount. FWIW, the > seqcount write in receive_mergeable() should, on modern x86, > translate to two non-atomic adds and two compiler barriers, so > overhead is not expected to be meaningful. > > We can move to sysfs and this would simplify or eliminate much of the > above, including most of (1) - (4). I believe our choices for what to > do for the next patchset include: > (a) Use debugfs as is currently done, removing any optional features > listed above that are deemed unnecessary. > > (b) Add a per-netdev sysfs attribute group to net_device->sysfs_groups. > Each attribute would display the mergeable packet buffer size for a given > RX queue, and there would be max_queue_pairs attributes in total. This > is already supported by net/core/net-sysfs.c:netdev_register_kobject(), > but means that we would have a static set of per-RX queue files for > all RX queues supported by the netdev, rather than dynamically displaying > only the files corresponding to enabled RX queues (e.g., when # of RX > queues is changed by ethtool -L <device>). For an example of this > approach, see drivers/net/bonding/bond_sysfs.c. > > (c) Modify struct netdev_rx_queue to add virtio-net EWMA fields directly, > and modify net-sysfs.c to manage the new fields. Unlike (b), this approach > supports the RX queue resizing in (3) but means putting virtio-net info > in netdev_rx_queue, which currently has only device-independent fields. Can't we add struct attribute * to netdevice, and pass that in when creating the kobj? > My preference would be (b): try using sysfs and adding a device-specific > attribute group to the virtio-net netdevice (stored in the existing > 'sysfs_groups' field and supported by net-sysfs). This would avoid > adding virtio-net specific information to net-sysfs. What would you > prefer (or is there a better way than the approaches above)? Thanks! > > Best, > > Mike _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
