linux-kernel - Re: [Intel-IOMMU 02/10] Library routines for handling pre-allocated pool of objects

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Message-ID: <20070604235105.GA13390@linux-os.sc.intel.com>
Date:	Mon, 4 Jun 2007 16:51:05 -0700
From:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	linux-kernel@...r.kernel.org, akpm@...l.org, ak@...e.de,
	gregkh@...e.de, muli@...ibm.com, asit.k.mallick@...el.com,
	suresh.b.siddha@...el.com, arjan@...ux.intel.com,
	ashok.raj@...el.com, shaohua.li@...el.com, davem@...emloft.net
Subject: Re: [Intel-IOMMU 02/10] Library routines for handling pre-allocated pool of objects

On Mon, Jun 04, 2007 at 07:43:54PM -0400, Jeff Garzik wrote:
> On Mon, Jun 04, 2007 at 04:06:49PM -0700, Keshavamurthy, Anil S wrote:
> > On Mon, Jun 04, 2007 at 06:57:14PM -0400, Jeff Garzik wrote:
> > > you should add logic to free resources here (or queue_work to free the
> > > resources), if the pool grows beyond a certain size.
> 
> > Can be added as an add on, testing showed that pool 
> > grows to a certain size and will not grow beyond that 
> > as we tend to reuse the elements.
> 
> Yes, but is it possible?  If no, what part of the code guarantees the
> pool is limited?
> 
> We should not merge code that allows the pool to grow without bound.
> In-house testing certainly never covers all the cases seen in the
> field, so I wouldn't make too many assumptions based on that.  Some
> vendor will inevitably build a $BigNum system where the IOMMU is very
> heavily used.

No problem, I can add the code to free the pool element if
the curr_count ever goes greater than (min_count + 2 * grow_count)
then bring the curr_count to min_count + grow_count by freeing 
some pool objects.

A patch which will apply to this current patch will follow soon.

Thanks Jeff for making your case stronger :)

-Anil


> 
> 	Jeff
> 
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