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)
