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Date: Thu, 23 Apr 2009 18:55:31 -0400 (EDT)
From: Christoph Lameter <cl@linux.com>
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To: David Rientjes <rientjes@google.com>
cc: Pekka Enberg <penberg@cs.helsinki.fi>,
       Randy Dunlap <randy.dunlap@oracle.com>, Nick Piggin <npiggin@suse.de>,
       linux-kernel@vger.kernel.org
Subject: Re: [patch 2/2] slub: add
 Documentation/ABI/testing/sysfs-kernel-slab
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On Thu, 23 Apr 2009, David Rientjes wrote:

> I'm more concerned with the userspace API.  You're comfortable with
> letting userspace determine what allocator the kernel is using either by
> testing for the presence of certain slub or slqb-specific files or
> checking the config?

Why would userspace have to test? If the fields have the same semantics
then we are fine.

> That should be fine since there's parity among the files that both
> allocators share, but seems fragile if an allocator adds a file that was
> previously only applicable to the other or the API happens to change.

Right. The newly added file must not be in use by another allocator.

> My thinking was that /sys/kernel/slqb would be a permanent reference point
> that userspace could easily test to determine what API is available.

The API is hopefully generic enought to accomodate all allocators.