[PATCH] powerpc: align DTL buffer to AMS boundary

[Nishanth Aravamudan]

On 13.04.2011 [15:59:44 +0100], David Laight wrote:
> > From: 
> > linuxppc-dev-bounces+david.laight=aculab.com at lists.ozlabs.org 
> > [mailto:linuxppc-dev-bounces+david.laight=aculab.com at lists.ozl
> > abs.org] On Behalf Of Nishanth Aravamudan
> > Sent: 13 April 2011 15:53
> > To: Ben Herrenschmidt
> > Cc: linuxppc-dev at ozlabs.org; Paul Mackerras; Anton Blanchard
> > Subject: [PATCH] powerpc: align DTL buffer to AMS boundary
> > 
> > PAPR specifies that DTL buffers can not cross AMS environments (aka
> CMO
> > in the PAPR) and can not cross a memory entitlement granule boundary
> > (4k)....
> 
> How big is the buffer being allocated?
> If it is much less than 4k then it might be worth allocating
> a buffer of the correct size, and only if that crosses a 4k boundary
> allocate the larger buffer.

Currently, DISPATCH_LOG_BYTES is 4k (which I assume was actually in
deference to this requirement).

> Also, if the buffer is ever freed, the actual base address is needed
> for the free.

I didn't see any free patch for this sequence of code -- which make
sense as this allocation occurs under a for_each_possible_cpu loop.

Thanks for the feedback,
Nish