Re: [PATCH 1/2 v2] ASoC: soc-cache: block based rbtree compression

[Mark Brown <broonie@opensource.wolfsonmicro.com>]

On Tue, May 03, 2011 at 04:07:42PM +0200, Takashi Iwai wrote:
> Mark Brown wrote:

> > If we can't get the data laid out in a contiguous array in memory then
> > we have to gather the data for transmit in the I/O code which is
> > painful and wasteful.

> But it's just a matter of CPU usage to look for the caches.
> Well, what I don't understand is the text you wrote:

No, as I said in my initial reply the big win is I/O bandwidth from
block writes.  There will also be a memory and consequent dcache win
from reducing the size of the data structure but that is likely to be
dwarfed by any write coalescing.

> | This isn't about CPU usage, it's about I/O bandwidth which is a big
> | concern in situations like resume where you can be bringing the device
> | back up from cold.

> How does the contiguous memory layout inside the cache management
> reduce the I/O bandwidth...?

If the data is laid out contiguously then we can easily send it to the
chip in one block.