linux-kernel - Re: [RFC][PATCH v1 5/9] ima: allocating iint improvements

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Date:	Wed, 1 Feb 2012 11:58:54 -0500
From:	Eric Paris <eparis@...isplace.org>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	linux-security-module@...r.kernel.org,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	David Safford <safford@...son.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [RFC][PATCH v1 5/9] ima: allocating iint improvements

On Mon, Jan 30, 2012 at 5:14 PM, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> From: Dmitry Kasatkin <dmitry.kasatkin@...el.com>
>

>  static struct rb_root integrity_iint_tree = RB_ROOT;
> -static DEFINE_SPINLOCK(integrity_iint_lock);
> +static DEFINE_RWLOCK(integrity_iint_lock);
>  static struct kmem_cache *iint_cache __read_mostly;

Has any profiling been done here?   rwlocks have been shown to
actually be slower on multi processor systems in a number of cases due
to the cache line bouncing required.  I believe the current kernel
logic is that if you have a short critical section and you can't show
profile data the rwlocks are better, just stick with a spinlock.
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