On Thu, Apr 14, 2016 at 02:59:16PM -0400, David Miller wrote: > From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> > Date: Thu, 14 Apr 2016 14:00:49 -0300 > > > Em 14-04-2016 10:03, Neil Horman escreveu: > >> On Wed, Apr 13, 2016 at 11:05:32PM -0400, David Miller wrote: > >>> From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> > >>> Date: Fri, 8 Apr 2016 16:41:26 -0300 > >>> > >>>> 1st patch is a preparation for the 2nd. The idea is to not call > >>>> ->sk_data_ready() for every data chunk processed while processing > >>>> packets but only once before releasing the socket. > >>>> > >>>> v2: patchset re-checked, small changelog fixes > >>>> v3: on patch 2, make use of local vars to make it more readable > >>> > >>> Applied to net-next, but isn't this reduced overhead coming at the > >>> expense of latency? What if that lower latency is important to the > >>> application and/or consumer? > >> Thats a fair point, but I'd make the counter argument that, as it > >> currently > >> stands, any latency introduced (or removed), is an artifact of our > >> implementation rather than a designed feature of it. That is to say, > >> we make no > >> guarantees at the application level regarding how long it takes to > >> signal data > >> readines from the time we get data off the wire, so I would rather see > >> our > >> throughput raised if we can, as thats been sctp's more pressing > >> achilles heel. > >> > >> > >> Thats not to say I'd like to enable lower latency, but I'd rather have > >> this now, > >> and start pondering how to design that in. Perhaps we can convert the > >> pending > >> flag to a counter to count the number of events we enqueue, and call > >> sk_data_ready every time we reach a sysctl defined threshold. > > > > That and also that there is no chance of the application reading the > > first chunks before all current ToDo's are performed by either the bh > > or backlog handlers for that packet. Socket lock won't be cycled in > > between chunks so the application is going to wait all the processing > > one way or another. > > But it takes time to signal the wakeup to the remote cpu the process > was running on, schedule out the current process on that cpu (if it > has in fact lost it's timeslice), and then finally look at the socket > queue. > > Of course this is all assuming the process was sleeping in the first > place, either in recv or more likely poll. > > I really think signalling early helps performance. I see. Okay, I'll revisit this, thanks. Marcelo -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
