Re: [PATCH v9 6/6] drm/i915: Cache last IRQ seqno to reduce IRQ overhead

Maarten Lankhorst
2016-06-07T12:47:45Z

Op 01-06-16 om 19:07 schreef John.C.Harrison@Intel.com:
> From: John Harrison <John.C.Harrison@Intel.com>
>
> The notify function can be called many times without the seqno
> changing. Some are to prevent races due to the requirement of not
> enabling interrupts until requested. However, when interrupts are
> enabled the IRQ handler can be called multiple times without the
> ring's seqno value changing. E.g. two interrupts are generated by
> batch buffers completing in quick succession, the first call to the
> handler processes both completions but the handler still gets executed
> a second time. This patch reduces the overhead of these extra calls by
> caching the last processed seqno value and early exiting if it has not
> changed.
How significant is this overhead?

Patch looks reasonable otherwise.

~Maarten