netdev - Re: RFC: Nagle latency tuning

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Message-ID: <20080922203042.GY25711@one.firstfloor.org>
Date:	Mon, 22 Sep 2008 22:30:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	David Miller <davem@...emloft.net>
Cc:	csnook@...hat.com, andi@...stfloor.org, rick.jones2@...com,
	netdev@...r.kernel.org
Subject: Re: RFC: Nagle latency tuning

On Mon, Sep 22, 2008 at 04:09:12AM -0700, David Miller wrote:
> From: David Miller <davem@...emloft.net>
> Date: Mon, 22 Sep 2008 03:49:33 -0700 (PDT)
> 
> > I'll try to figure out why Andi's patch doesn't behave as expected.
> 
> Andi's patch uses proc_dointvec_jiffies, which is for sysctl values
> stored as seconds, whereas these things are used to record values with
> smaller granulatiry, are stored in jiffies, and that's why we get zero
> on read and writes have crazy effects.

Oops. Assume me with brown paper bag etc.etc.

It was a typo for proc_dointvec_ms_jiffies


> 
> Also, as Andi stated, this is not the way to deal with this problem.
> 
> So we have a broken patch, which even if implemented properly isn't the
> way forward, so I consider this discussion dead in the water until we
> have some test cases.

The patch is easy to fix with a s/_jiffies/_ms_jiffies/g

Also it was more intended for him to play around and get some data
points. I guess for that it's still useful.

Also while for that it's probably not the right solution, but 
I could imagine in some other situations where it might be useful
to tune these values. After all they are not written down in stone.
I wonder if it would even make sense to consider hr timers for TCP
now.

=Andi
-- 
ak@...ux.intel.com
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