Hans, On Fri, Jan 24, 2020 at 08:21:54PM +0100, Hans Petter Selasky wrote: H> > If a driver has interrupt moderation than epoch batching counter H> > basically won't ever grow over 1. It kicks in only of driver doesn't H> > have it, or receives interrupts at a very high rate. H> H> Depending on the load an interrupt imposes, this batching counter may H> cause epochs to last for a long time. Have you considered using ticks H> for this instead? I.E. if the congestion lasts more than two ticks, then H> re-acquire the EPOCH? H> H> For example if the network controller spends more time processing H> packets then there is between interrupts, then this unconditional 1000x H> thing can be quite dangerous.
I didn't try using ticks instead of execution counter. It could be ticks would be better. Needs more experiments. H> > H> 2) You need to make a new request function for interrupts which take a H> > H> pointer to an EPOCH and replace that IH_NET in hflags! H> > H> > Initially I did that way, but then pondered over this approach and have H> > abandoned it. Most likely we will have just few globally recognized H> > epochs in the kernel. And even less might be associated with interrupt H> > handlers. Complexity and performance impact of using a pointer are H> > noted by Drew in D23347. H> H> Let not the network epoch become the new Giant of EPOCH's. There might H> be realtime constraints for EPOCH's aswell. Epoch isn't a lock, so it can't become the new Giant. -- Gleb Smirnoff _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
