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Date: Mon, 22 Dec 2008 10:49:43 +1030 From: Rusty Russell <rusty@...tcorp.com.au> To: Jens Axboe <jens.axboe@...cle.com> Cc: Tejun Heo <tj@...nel.org>, Jerome Marchand <jmarchan@...hat.com>, linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux-foundation.org> Subject: per-cpu stats in block device: overkill? Hi Jens, Tejun, Jerome, I've been auditing alloc_per_cpu users, and got to genhd. The code is fairly complex, but I can't help wondering if per-cpu counters are overkill. After all, we have a single queue lock. The reason I care is that I'm changing alloc_per_cpu to use the static per-cpu area: at 40/80 bytes (32/64 bit) per stat, we'd be restricted to a few hundred disks unless the percpu area is enlarged (in current patches, a cmdline param). Or, I can change genhd to use big_percpu_alloc which will use the current inefficient dynamic per-cpu system until we get dynamic per-cpu regions (if ever). Cheers, Rusty. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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