linux-kernel - Re: [Intel-IOMMU 02/10] Library routine for pre-allocat pool handling

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Date:	Fri, 8 Jun 2007 15:18:03 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	Andreas Kleen <ak@...e.de>, linux-kernel@...r.kernel.org,
	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,
	clameter@....com
Subject: Re: [Intel-IOMMU 02/10] Library routine for pre-allocat pool handling

On Fri, Jun 08, 2007 at 02:42:07PM -0700, Andrew Morton wrote:
> I'd say just remove the whole thing and use kmem_cache_alloc().

We will try that.

> Put much effort into removing the GFP_ATOMIC and using GFP_NOIO instead:
> there's your problem right there.

As these are called from interrupt handlers, we can't use GFP_NOIO.

> If for some reason you really can't do that (and a requirement for
> allocation-in-interrupt is the only valid reason, really) and if you indeed
> can demonstrate memory allocation failures with certain workloads then
> let's take a look at that.  As I said, attaching a reserve pool to your
> slab cache might be a suitable approach.  But none of these things are

I agree. We are better off with enhancing slab infrastructure for this, if
needed.

> magic: if memory allcoation failures or deadlocks or livelocks are
> demonstrable with the reserves absent, then they'll also be possible with
> the reserves present.
> 
> Unless you use mempools, and can sleep.
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