On Wed, Sep 23, 2020 at 04:09:30PM -0400, Konrad Rzeszutek Wilk wrote:

On Tue, Sep 22, 2020 at 09:01:25AM +0200, SeongJae Park wrote:

quoted

From: SeongJae Park <redacted>

Persistent grants feature provides high scalability.  On some small
systems, however, it could incur data copy overhead[1] and thus it is
required to be disabled.  But, there is no option to disable it.  For
the reason, this commit adds a module parameter for disabling of the
feature.

Would it be better suited to have it per guest?

I think having a per-backend policy that could be specified at the
toolstack level would be nice, but I see that as a further
improvement.

Having a global backend domain policy of whether persistent grants are
enabled or not seems desirable, and if someone wants even more fine
grained control this change is AFAICT not incompatible with a
per-backend option anyway.

Roger.