Re: [PATCH 21/29] ioat2,3: dynamically resize descriptor ring

Dan Williams
2009-09-15T23:07:08Z

On Mon, Sep 14, 2009 at 8:00 AM, Sosnowski, Maciej
<maciej.sosnowski@intel.com> wrote:
> Making the max_alloc_order a module parameter gives impression
> that it can be modified by an user, including making it larger than default.
> The default is however its maximum value, which may be confusing.
> Why not to use parameter only as the upper limit?

It is the upper limit.

The user can limit the upper size of the descriptor ring by setting
this to a value less than 16. By default it is the maximum ring size
that the driver/hardware* supports. Specifying values greater than 16
are not supported by the so we need enforce a ceiling at 16.

--
Dan

* We could support ring sizes larger than 1 << 16 but we would need to
extra logic to ensure that the pending count never exceeded 1 << 16.
Simpler I think to just limit the maximum ring size.