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Message-ID: <20141027213523.799da09c@redhat.com> Date: Mon, 27 Oct 2014 21:35:23 +0100 From: Jesper Dangaard Brouer <brouer@...hat.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: brouer@...hat.com, Alexander Duyck <alexander.duyck@...il.com>, Alexei Starovoitov <ast@...mgrid.com>, Eric Dumazet <edumazet@...gle.com>, Network Development <netdev@...r.kernel.org>, Christoph Lameter <cl@...ux.com> Subject: Re: irq disable in __netdev_alloc_frag() ? On Wed, 22 Oct 2014 20:51:16 -0700 Eric Dumazet <eric.dumazet@...il.com> wrote: > On my hosts, this hard irq masking is pure noise. On my hosts I can measure a significant difference between using local_irq_disable() vs. local_irq_save(flags) * 2.860 ns cost for local_irq_{disable,enable} * 14.840 ns cost for local_irq_save()+local_irq_restore() This is quite significant in my nanosec world ;-) > What CPU are you using Alexander ? I'm using a E5-2695 (Ivy-bridge) You can easily reproduce my results on your own system with my time_bench_sample module here: https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/time_bench_sample.c#L173 > Same could be done with some kmem_cache_alloc() : SLAB uses hard irq > masking while some caches are never used from hard irq context. Sounds interesting. -- 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 from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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