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Date: Fri, 27 Apr 2012 10:17:17 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Tejun Heo <tj@kernel.org>
CC: Yanmin Zhang <yanmin_zhang@linux.intel.com>,
        ShuoX Liu <shuox.liu@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Christoph Lameter <cl@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH] percpu, x86: don't use PMD_SIZE as embedded atom_size
 on 32bit
References: <4F97BA98.6010001@intel.com> <20120425222429.GE8989@google.com> <1335405672.14538.135.camel@ymzhang.sh.intel.com> <20120426224946.GG27486@google.com> <1335488964.14538.159.camel@ymzhang.sh.intel.com> <1335516994.14538.160.camel@ymzhang.sh.intel.com> <20120427165356.GA26595@google.com>
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On 04/27/2012 09:53 AM, Tejun Heo wrote:
>  
> +		/*
> +		 * If PSE is available, use PMD_SIZE for atom_size so that
> +		 * embedded percpu areas are aligned to PMD.  This, in the
> +		 * future, can also allow using PMD mappings in vmalloc
> +		 * area.  Use PAGE_SIZE on 32bit as vmalloc space is highly
> +		 * contended and large vmalloc area alloc can easily fail.
> +		 */
> +		atom_size = PAGE_SIZE;
> +#ifdef CONFIG_X86_64
> +		if (cpu_has_pse)
> +			atom_size = PMD_SIZE;
> +#endif

Just make it PAGE_SIZE on i386 and PMD_SIZE on x86-64; keep the behavior
consistent.  !cpu_has_pse on x86-64 is an abnormal situation (I think it
applies to Xen, pretty much.)

Other than that,

Acked-by: H. Peter Anvin <hpa@zytor.com>

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.