linux-kernel - Re: [PATCH] x86: Use clflush() instead of wbinvd() whenever possible when changing mapping

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Message-ID: <4A75BD2A.9050404@vmware.com>
Date:	Sun, 02 Aug 2009 18:22:02 +0200
From:	Thomas Hellström <thellstrom@...are.com>
To:	Pavel Machek <pavel@....cz>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"venkatesh.pallipadi@...el.com" <venkatesh.pallipadi@...el.com>
Subject: Re: [PATCH] x86: Use clflush() instead of wbinvd() whenever	possible
 when changing mapping

Pavel Machek skrev:
> On Fri 2009-07-24 09:53:01, Thomas Hellstrom wrote:
>   
>> The current code uses wbinvd() when the area to flush is > 4MB. Although this
>> may be faster than using clflush() the effect of wbinvd() on irq
>> latencies
>>     
>
> You are slowing the kernel down, and you did not write down the
> reasons. bad.
>
>   
I may slow the kernel down or speed it up depending on your hardware 
configuration. The reasons should be quite obvious if you read the 
discussion following the patch.

/Thomas

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