Re: [Xen-devel] [RFC] irq rate limit

[Qing He <qing.he@xxxxxxxxx>]

On Wed, 2009-09-09 at 16:48 +0800, Keir Fraser wrote:
> On 09/09/2009 09:48, "Qing He" <qing.he@xxxxxxxxx> wrote:
> 
> > This is a poc patch of guest irq ratelimit. The main motivation is
> > to ensure Xen's responsiveness during an irq storm, that caused by
> > improper hardware or drivers. If one interrupt is fired at a high
> > rate (>10k/10ms in the poc), it is disabled until the next periodic
> > timer_fn. A global generation counter is used to minimize overhead.
> 
> What's the generation counter for? Why not just zero desc->rl_cnt in the
> timer handler?

If zeroing desc->rl_cnt in the timer handler, we have to zero that of
all irqs. If the numbers of possible irqs is big or sparse, it's a bit
painful.

Also, possibly it needs to be moved out of irq_desc and use atomic_t to
avoid spinlocking every irq_desc in the timer handler.

Thanks,
Qing

> 
>  -- Keir
> 
> 

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