On Thu, Jan 11, 2018 at 09:13:42PM +0000, Dmitry Safonov wrote: > On Thu, 2018-01-11 at 12:53 -0800, Eric Dumazet wrote: > > On Thu, Jan 11, 2018 at 12:46 PM, Dmitry Safonov <d...@arista.com> > > wrote: > > > On Thu, 2018-01-11 at 12:40 -0800, Linus Torvalds wrote: > > > > On Thu, Jan 11, 2018 at 12:34 PM, Dmitry Safonov <d...@arista.com > > > > > > > > > wrote: > > > > > > > > > > I could try to write a PoC for that.. > > > > > What should be the trigger to fall into workqueue? > > > > > How to tell if there're too many softirqs of the kind? > > > > > > > > I suspect it would have to be time-based, probably using the > > > > scheduler clock. > > > > > > I thought about this, but I was a bit afraid of how much pricey it > > > would be recalculate it each clock. Well, might just try to write > > > that > > > and measure the impact. > > > > > > > Most softirqs are really really small. So just counting them > > > > probably > > > > isn't all that meaningful, although the count is good as a > > > > fallback > > > > (as shown by the jiffy issues). > > > > > > > > The good news is that we only have a fairly small handful of > > > > softirqs, > > > > so counting/timing them separately is still mainly a pretty small > > > > array (which needs to be percpu, of course). > > > > Note that using (scheduler) clock might also help to break > > net_rx_action() > > not on a stupid netdev_budget, but on a more precise time limit as > > well. > > > > netdev_budget of 300 packets is quite big :/ > > > > (The time_limit based on jiffies + 2 does not work on hosts with one > > cpu, since jiffies wont make progress while net_rx_action() is > > running) > > Thanks for the details, Eric. > I'll try to come up with poc if no one beats me at it.
I just gave it a try. Sorry I couldn't resist :-s
