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Re: [PATCH] use mmiowb in tg3_poll

To: hadi@xxxxxxxxxx
Subject: Re: [PATCH] use mmiowb in tg3_poll
From: Jesse Barnes <jesse.barnes@xxxxxxxxx>
Date: Tue, 31 May 2005 09:45:36 -0700
Cc: Arthur Kepner <akepner@xxxxxxx>, Lennert Buytenhek <buytenh@xxxxxxxxxxxxxx>, netdev@xxxxxxxxxxx, gnb@xxxxxxx
In-reply-to: <1117544022.6134.54.camel@xxxxxxxxxxxxxxxxxxxxx>
References: <200410211628.06906.jbarnes@xxxxxxxxxxxx> <Pine.LNX.4.61.0505300925570.11645@xxxxxxxxxx> <1117544022.6134.54.camel@xxxxxxxxxxxxxxxxxxxxx>
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On Tuesday, May 31, 2005 5:53 am, jamal wrote:
> Did i read correctly that your reads are about 2x more expensive than
> the writes?

The test above just measures the difference between using a full PIO 
read to ensure write ordering vs. the lighter weight mmiowb call.  As 
for your question though, non-relaxed reads are very expensive on the 
Altix platform due to its highly distributed NUMA I/O architecture.  
The _relaxed variants can be quite fast however, and can be used 
anytime a PIO read doesn't imply anything about previous DMA 
transactions.

Jesse

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