To: Dave Airlie <airlied@redhat.com>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com,
       arjan@linux.intel.com, thomas@tungstengraphics.com
Subject: Re: [PATCH] x86: create array based interface to change page attribute
References: <1206940788.7250.13.camel@clockmaker.usersys.redhat.com>
From: Andi Kleen <andi@firstfloor.org>
Date: 31 Mar 2008 09:25:12 +0200
In-Reply-To: <1206940788.7250.13.camel@clockmaker.usersys.redhat.com>
Message-ID: <87myof8ief.fsf@basil.nowhere.org>
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Dave Airlie <airlied@redhat.com> writes:
>  
> +#define CPA_FLUSHTLB 1
> +#define CPA_ARRAY 2

I don't think CPA_ARRAY should be a separate case. Rather single
page flushing should be an array with only a single entry. pageattr
is already very complex, no need to make add more special cases.
> +
> +		/*
> +		 * Only flush present addresses:
> +		 */
> +		if (pte && (pte_val(*pte) & _PAGE_PRESENT))
> +			clflush_cache_range((void *) *addr, PAGE_SIZE);

Also it is doubtful clflush really makes sense on a large array. Just
doing wbinvd might be faster then. Or perhaps better supporting Self-Snoop
should be revisited, that would at least eliminate it on most Intel 
CPUs.

-Andi
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