block: add a new flag to make request complete on submitted cpu
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From: Shaohua Li on 21 Dec 2009 20:40 On Mon, Dec 21, 2009 at 08:12:28PM +0800, Jens Axboe wrote: > On Mon, Dec 21 2009, Jens Axboe wrote: > > On Mon, Dec 21 2009, Shaohua Li wrote: > > > We already have a QUEUE_FLAG_SAME_COMP, which makes request complete > > > on the first cpu of a mc/ht, but this isn't sufficient. In a system > > > with fast block devices (intel SSD), it turns out the first cpu is > > > bottlenect. Add a flag to make request complete on cpu where request > > > is submitted. The flag implies QUEUE_FLAG_SAME_COMP. By default, it is off. > > > > It was a lazy trick to avoid doing any round robin work in there. > > > > > My test machine has two CPUs and 4 intel SSD. Without the new flag, > > > the io thoughput is about 400m/s; with it, the thoughput is about 500m/s. > > > > So I think we should just fix it, I still think the group logic makes > > sense. But instead of always going for the first one, let it complete > > locally if part of the group, if not send to specific submitter CPU. > > Is this enough? It renames cpu to local_cpu and ccpu to target_cpu to > make things clearer to read, the real change is that we allow local > completion if the cpu matches OR the group matches. No. Interrupt is fired on one CPU, so the change is a nop. All requests are handled by the CPU directed the interrupt. AHCI supports multiple MSI but not support per-vector mask, which makes it's hard to add multiple MSI support. Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |