From: Loic Prylli <loic@myri.com>
To: Brice Goglin <brice@myri.com>
Cc: Arjan van de Ven <arjan@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
netdev@vger.kernel.org,
"venkatesh.pallipadi@intel.com" <venkatesh.pallipadi@intel.com>
Subject: Re: howto use ioremap_wc?
Date: Mon, 02 Jun 2008 14:18:04 -0400 [thread overview]
Message-ID: <4844395C.2010900@myri.com> (raw)
In-Reply-To: <48441F73.5040005@myri.com>
On 06/02/2008 12:27 PM, Brice Goglin wrote:
> Arjan van de Ven wrote:
>
>> Ok this leads to a question: since write combining is effectively an
>> extension (eg relaxation) to uncached, how much do you care if you
>> actually get uncached? Eg can you just use the "WC" function even for
>> the case where you get an uncached mapping ?
>>
>>
>
> WC is strictly required for our "wcfifo" path,
To be more accurate about the above statement, that codepath will still
work correctly even if the mapping ends-up being uncached, but that
could lead to a 16X slowdown on some machines, since that path was
really designed for the WC case.
Anyway that codepath does not really matter as Brice mentioned
afterwards :-)
> but this path is actually
> not so important nowadays. It is disabled by default and might even be
> removed in the future. So, no, myri10ge itself does not really need to
> know whether the mapping is actually WC.
>
Loic
next prev parent reply other threads:[~2008-06-02 18:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-31 9:02 howto use ioremap_wc? Brice Goglin
2008-06-01 1:54 ` Arjan van de Ven
2008-06-02 16:27 ` Brice Goglin
2008-06-02 18:18 ` Loic Prylli [this message]
2008-06-03 2:18 ` Arjan van de Ven
2008-06-05 4:53 ` Roland Dreier
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