Re: [PATCH RESEND v2 2/5] dma-pool: allow user to disable atomic pool

Baoquan He
2021-12-13T08:16:53Z

On 12/13/21 at 08:44am, Christoph Hellwig wrote:
> On Tue, Dec 07, 2021 at 11:07:47AM +0800, Baoquan He wrote:
> > In the current code, three atomic memory pools are always created,
> > atomic_pool_kernel|dma|dma32, even though 'coherent_pool=0' is
> > specified in kernel command line. In fact, atomic pool is only
> > necessary when CONFIG_DMA_DIRECT_REMAP=y or mem_encrypt_active=y
> > which are needed on few ARCHes.
>
> And only these select the atomic pool, so it won't get created otherwise.
> What problem are you trying to solve?

This tries to make "coherent_pool=0" behave normally. As you see,
'coherent_pool=0' will behave like no 'coherent_pool' being specified.
This is not consistent with other similar kernel parameter, e.g cma=.

At the beginning, I planned to add a knob to allow user to disable one
or all atomic pool. Later I changed. However I think this patch makes
sense on fixing the a little bizarre behaviour, 'coherent_pool=0' but
still get atomic pool created.

I can drop it if you think it's unnecessary.