Re: [PATCH net-next v5] rtnetlink: Support fine-grained netdevice bulk deletion

On 12/8/21 5:04 PM, Jakub Kicinski wrote:

On Wed, 8 Dec 2021 16:43:28 -0700 David Ahern wrote:

quoted

On 12/8/21 2:47 PM, Lahav Schlesinger wrote:

quoted

No visible changes from what I saw, this API is as fast as group
deletion. Maybe a few tens of milliseconds slower, but it's lost in the
noise.
I'll run more thorough benchmarks to get to a more conclusive conclusion.

Also just pointing out that the sort will be needed even if we pass an
array (IFLA_IFINDEX_LIST) instead.
Feels like CS 101, but do you have a better approach for detecting
duplicates in an array? I imagine a hash table will be slower as it will
need to allocate a node object for each device (assuming we don't want
to add a new hlist_node to 'struct net_device' just for this)  

I think marking the dev's and then using a delete loop is going to be
the better approach - avoid the sort and duplicate problem. I use that
approach for nexthop deletes:

https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/net/ipv4/nexthop.c#n1849

Find a hole in net_device struct in an area used only for control path
and add 'bool grp_delete' (or a 1-bit hole). Mark the devices on pass
and delete them on another.

If we want to keep state in the netdev itself we can probably piggy
back on dev->unreg_list. It should be initialized to empty and not
touched unless device goes thru unregister.

isn't that used when the delink function calls unregister_netdevice_queue?