On Thu, 11 Dec 2014 09:03:24 -0600 (CST) Christoph Lameter <cl@xxxxxxxxx> wrote: > On Thu, 11 Dec 2014, Jesper Dangaard Brouer wrote: > > > It looks like an impressive saving 116 -> 60 cycles. I just don't see > > the same kind of improvements with my similar tests[1][2]. > > This is particularly for a CONFIG_PREEMPT kernel. There will be no effect > on !CONFIG_PREEMPT I hope. > > > I do see the improvement, but it is not as high as I would have expected. > > Do you have CONFIG_PREEMPT set? Yes. $ grep CONFIG_PREEMPT .config CONFIG_PREEMPT_RCU=y CONFIG_PREEMPT_NOTIFIERS=y # CONFIG_PREEMPT_NONE is not set # CONFIG_PREEMPT_VOLUNTARY is not set CONFIG_PREEMPT=y CONFIG_PREEMPT_COUNT=y Full config here: http://people.netfilter.org/hawk/kconfig/config01-slub-fastpath01 I was expecting to see at least (specifically) 4.291 ns improvement, as this is the measured[1] cost of preempt_{disable,enable] on my system. [1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/time_bench_sample.c -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org 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>