Hi Willy, On Wed, May 19, 2021 at 07:07:54PM +0100, Matthew Wilcox wrote: > On Wed, May 19, 2021 at 07:57:55PM +0200, Nicolas Saenz Julienne wrote: > > To minimize trace's effect on isolated CPUs. That is, CPUs were only a > > handful or a single, process are allowed to run. Introduce a new trace > > option: 'poll-rb'. > > maybe this should take a parameter in ms (us?) saying how frequently > to poll? it seems like a reasonable assumption that somebody running in > this kind of RT environment would be able to judge how often their > monitoring task needs to collect data. +1 (yes please). > > [1] The IPI, in this case, an irq_work, is needed since trace might run > > in NMI context. Which is not suitable for wake-ups. > > could we also consider a try-wakeup which would not succeed if in NMI > context? or are there situations where we only gather data in NMI > context, and so would never succeed in waking up? if so, maybe > schedule the irq_work every 1000 failures to wake up. We'd like to reduce overhead on the isolated (as in isolcpus=) CPUs as much as possible (but yes this option was suggested).
