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To: Greg KH <greg@kroah.com>, mp3@de.ibm.com
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: statistics infrastructure (in -mm tree) review
References: <20060613232131.GA30196@kroah.com>
	<20060613234739.GA30534@kroah.com>
From: Andi Kleen <ak@suse.de>
Date: 14 Jun 2006 07:04:35 +0200
In-Reply-To: <20060613234739.GA30534@kroah.com>
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Greg KH <greg@kroah.com> writes:
> > + * exploiters don't update several statistics of the same entity in one go.
> > + */
> > +static inline void statistic_add(struct statistic *stat, int i,
> > +				 s64 value, u64 incr)
> > +{
> > +	unsigned long flags;
> > +	local_irq_save(flags);
> > +	if (stat[i].state == STATISTIC_STATE_ON)
> > +		stat[i].add(&stat[i], smp_processor_id(), value, incr);


Indirect call in statistics hotpath?  You know how slow this is 
on IA64 and even on other architectures it tends to disrupt 
the pipeline.

Also on i386 the u64s generate quite bad code.

That looks like a really bad implementation that shouldn't be used
anywhere.

-Andi