netdev - Re: [PATCH] [RESEND] iproute2 : invalid burst/cburst calculation with hrtimers

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Message-Id: <200902050124.05969.denys@visp.net.lb>
Date:	Thu, 5 Feb 2009 01:24:05 +0200
From:	Denys Fedoryschenko <denys@...p.net.lb>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Stephen Hemminger <shemminger@...ux-foundation.org>,
	netdev@...r.kernel.org
Subject: Re: [PATCH] [RESEND] iproute2 : invalid burst/cburst calculation with hrtimers

On Thursday 05 February 2009 00:49:29 Jarek Poplawski wrote:
> On Thu, Feb 05, 2009 at 12:26:46AM +0200, Denys Fedoryschenko wrote:
> ...
>
> > Maybe we can put note in documentation or even htb help output, that user
> > can increase precision with hrtimers enabled, by setting HZ variable?
>
> Hmm... I rather meant using burst and cburst params. But hrtimers are
> very hardware dependent, so it's hard to advise anything.
>
> Jarek P.

By default burst/cburst calculated depends on timer resolution, as i 
understood, by taking 4th parameter of /proc/net/psched, which as i 
understood - precision of hrtimer .

With hrtimers it is nanosecond resolution, precision is very high, but 
overhead too high too. And as i understand, maybe it can be problem, that htb 
still uses HZ variable in some cases like:
	return q->now + 2 * PSCHED_TICKS_PER_SEC / HZ;


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