Re: [PATCH v6 net-next 2/5] net: implement support for low latency socket polling

[Ben Hutchings <bhutchings@solarflare.com>]

On Wed, 2013-05-29 at 17:14 +0300, Or Gerlitz wrote:
> On Wed, May 29, 2013 at 9:39 AM, Eliezer Tamir
> <eliezer.tamir@linux.intel.com> wrote:
> > Adds a new ndo_ll_poll method and the code that supports and uses it.
> > This method can be used by low latency applications to busy poll Ethernet
> > device queues directly from the socket code. The value of sysctl_net_ll_poll
> > controls how many microseconds to poll. Set to zero to disable.
> 
> Unlike with TCP sockets, UDP sockets may receive packets from multiple
> sources and hence the receiving context may be steered to be executed
> on different cores through RSS or other Flow-Steering HW mechanisms
> which could mean different napi contexts for the same socket, is that
> a problem here? what's the severity?

Maybe ARFS could be extended so the driver can tell whether a UDP socket
it's steering for is connected or not.  Then for disconnected sockets
the driver can use a filter that only matches destination address.
(Though that's probably undesirable if the socket has SO_REUSEPORT set.)

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
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