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Re: realtime section bugs still around

To: Jason Newton <nevion@xxxxxxxxx>
Subject: Re: realtime section bugs still around
From: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Date: Tue, 31 Jul 2012 18:46:25 -0500
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <CAGou9MgMHbTPebFUDXdyLvrUr4T9wo-geNtaPUft9uUmOaju6Q@xxxxxxxxxxxxxx>
References: <CAGou9MgezsS=2+SngGWBJv5Npsuqacx1VPJwvMuf0FS+XnXt8A@xxxxxxxxxxxxxx> <20120730030333.GE2877@dastard> <CAGou9MheeBWxajd65szNfDB2L+VVoZ7SypEdUKj7np3L0H8fHA@xxxxxxxxxxxxxx> <CAGou9MgMHbTPebFUDXdyLvrUr4T9wo-geNtaPUft9uUmOaju6Q@xxxxxxxxxxxxxx>
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On 7/31/2012 6:01 PM, Jason Newton wrote:

> I'm still interested in finding out why streaming a few hundred MB to disk
> has so much over head in comparison to the calculations I do in userspace,

1.  md eats a lot of cycles at high data rates
2.  ATA overhead
3.  IRQ/MSI overhead
4.  Etc.

All these small bits add up to more than negligible CPU overhead at high
data rates.

-- 
Stan

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