linux-kernel - Re: [PATCH 22/25] Generic dynamic per cpu refcounting

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Message-ID: <m28v9kgsen.fsf@firstfloor.org>
Date:	Thu, 29 Nov 2012 10:45:04 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	Kent Overstreet <koverstreet@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-aio@...ck.org,
	linux-fsdevel@...r.kernel.org, zab@...hat.com, bcrl@...ck.org,
	jmoyer@...hat.com, axboe@...nel.dk, viro@...iv.linux.org.uk
Subject: Re: [PATCH 22/25] Generic dynamic per cpu refcounting

Kent Overstreet <koverstreet@...gle.com> writes:

> This implements a refcount with similar semantics to
> atomic_get()/atomic_dec_and_test(), that starts out as just an atomic_t
> but dynamically switches to per cpu refcounting when the rate of
> gets/puts becomes too high.

This will only work if you put on the same CPU as you get, right?
In this case I would rather use RCU. It's clearly unusable for anything 
blocking (or not get_cpu) Normally RCU already handles the "ref count for short non
blocking case"

Is that really true for AIO? It seems dubious.

-Andi


-- 
ak@...ux.intel.com -- Speaking for myself only
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