Hi Linus, Just wanted to give a heads-up on two regressions in 4.11-rc series. (1) page allocator optimization revert Mel Gorman and I have been playing with optimizing the page allocator, but Tariq spotted that we caused a regression for (NIC) drivers that refill DMA RX rings in softirq context. The end result was a revert, and this is waiting in AKPMs quilt queue: http://ozlabs.org/~akpm/mmots/broken-out/revert-mm-page_alloc-only-use-per-cpu-allocator-for-irq-safe-requests.patch (2) Busy softirq can cause userspace not to be scheduled I bisected the problem to a499a5a14dbd ("sched/cputime: Increment kcpustat directly on irqtime account"). See email thread with Subject: Bisected softirq accounting issue in v4.11-rc1~170^2~28 http://lkml.kernel.org/r/20170328101403.34a82fbf@xxxxxxxxxx I don't know the scheduler code well enough to fix this, and will have to rely others to figure out this scheduler regression. To make it clear: I'm only seeing this scheduler regression when a remote host is sending many many network packets, towards the kernel which keeps NAPI/softirq busy all the time. A possible hint: tool "top" only shows this in "si" column, while on v4.10 "top" also blames "ksoftirqd/N", plus "ps" reported cputime (0:00) seems wrong for ksoftirqd. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
