From: Tejun Heo <tj@kernel.org>
To: cl@linux-foundation.org, kmo@daterainc.com
Cc: linux-kernel@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 3/3] percpu-refcount: make percpu_ref based on longs instead of ints
Date: Sat, 20 Sep 2014 01:26:53 -0400 [thread overview]
Message-ID: <20140920052653.GB7926@mtj.dyndns.org> (raw)
In-Reply-To: <1410142342-8185-4-git-send-email-tj@kernel.org>
On Mon, Sep 08, 2014 at 11:12:22AM +0900, Tejun Heo wrote:
> percpu_ref is currently based on ints and the number of refs it can
> cover is (1 << 31). This makes it impossible to use a percpu_ref to
> count memory objects or pages on 64bit machines as it may overflow.
> This forces those users to somehow aggregate the references before
> contributing to the percpu_ref which is often cumbersome and sometimes
> challenging to get the same level of performance as using the
> percpu_ref directly.
>
> While using ints for the percpu counters makes them pack tighter on
> 64bit machines, the possible gain from using ints instead of longs is
> extremely small compared to the overall gain from per-cpu operation.
> This patch makes percpu_ref based on longs so that it can be used to
> directly count memory objects or pages.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Kent Overstreet <kmo@daterainc.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
Applied 1 and 3 to percpu/for-3.18.
Thanks.
--
tejun
next prev parent reply other threads:[~2014-09-20 5:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-08 2:12 [PATCHSET percpu/for-3.18] percpu-refcount: several improvements Tejun Heo
2014-09-08 2:12 ` [PATCH 1/3] percpu-refcount: improve WARN messages Tejun Heo
2014-09-08 2:12 ` [PATCH 2/3] percpu-refcount: implement percpu_ref_set_killed() Tejun Heo
2014-09-20 5:26 ` Tejun Heo
2014-09-08 2:12 ` [PATCH 3/3] percpu-refcount: make percpu_ref based on longs instead of ints Tejun Heo
2014-09-20 5:26 ` Tejun Heo [this message]
2014-09-20 5:31 ` [PATCH v2 " Tejun Heo
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