From: Rusty Russell <rusty@rustcorp.com.au>
To: Jens Axboe <jens.axboe@oracle.com>
Cc: Tejun Heo <tj@kernel.org>, Jerome Marchand <jmarchan@redhat.com>,
linux-kernel@vger.kernel.org,
Christoph Lameter <cl@linux-foundation.org>
Subject: per-cpu stats in block device: overkill?
Date: Mon, 22 Dec 2008 10:49:43 +1030 [thread overview]
Message-ID: <200812221049.43884.rusty@rustcorp.com.au> (raw)
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.
next reply other threads:[~2008-12-22 0:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-22 0:19 Rusty Russell [this message]
2008-12-22 1:55 ` per-cpu stats in block device: overkill? Tejun Heo
2008-12-22 3:56 ` Rusty Russell
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