On Thu, May 22, 2014 at 8:23 AM, Andi Kleen <a...@firstfloor.org> wrote: >> Hardware-interrupts during kernel are actually fairly common under >> network-intensive loads, even outside of idle (but idle is admittedly >> likely *the* most common one). Many network loads are fairly >> kernel-intensive. > > For network workloads we can arbitarily coalesce interrupts or just use NAPI > to lower the costs. No need to optimize network interrupts too much.
BS. Lots of network loads are latency-criticial, to the point that people sometimes actually turn off coalescing. But even with coalescing, it doesn't do crap for ping-pong kinds of loads that are not "interrupt storm from tons and tons of separate packets", but "lots of individual packets that are data-dependent", so you don't have new ones coming in while processing old ones. Ask Andy L. He had numbers. Interrupt overhead was quite big for him. And you ignored the real issue: special-casing idle is *stupid*. It's more complicated, and gives fewer cases where it helps. It's simply fundamentally stupid and wrong. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/