On Tue, 2018-01-23 at 11:22 -0500, David Miller wrote: > From: Paolo Abeni <[email protected]> > Date: Tue, 23 Jan 2018 11:13:52 +0100 > > > Hi, > > > > On Fri, 2018-01-19 at 16:46 +0100, Frederic Weisbecker wrote: > >> As per Linus suggestion, this take doesn't limit the number of occurences > >> per jiffy anymore but instead defers a vector to workqueues as soon as > >> it gets re-enqueued on IRQ tail. > >> > >> No tunable here, so testing should be easier. > >> > >> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git > >> softirq/thread-v3 > >> > >> HEAD: 6835e92cbd70ef4a056987d2e1ed383b294429d4 > > > > I tested this series in the UDP flood scenario, binding the user space > > process receiving the packets on the same CPU processing the related > > IRQ, and the tput sinks nearly to 0, like before Eric's patch. > > > > The perf tool says that almost all the softirq processing is done > > inside the workqueue, but the user space process is scheduled very > > rarely, while before this series, in this scenario, ksoftirqd and the > > user space process got a fair share of the CPU time. > > Do workqueue threads get a higher scheduling priority than user > processes?
As far as I can see, no: the workqueue thread has the same priority and nice level than the user space process. > Or is it that the workqueue execution is simply not yielding for some > reason? It's like that. I spent little time on it, so I haven't many data point. I'll try to investigate the scenario later this week. Cheers, Paolo
