Re: [Xen-devel] [RFC PATCH v1] Replace tasklets with per-cpu implementation.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.08.14 at 15:46, <konrad.wilk@xxxxxxxxxx> wrote:
> On Thu, Aug 28, 2014 at 01:39:54PM +0100, Jan Beulich wrote:
>> >>> On 27.08.14 at 19:58, <konrad.wilk@xxxxxxxxxx> wrote:
>> > The 'hvm_do_IRQ_dpci' is the on that is most often scheduled
>> > and run. The performance bottleneck comes from the fact that
>> > we take the same spinlock three times: tasklet_schedule,
>> > when we are about to execute the tasklet, and when we are
>> > done executing the tasklet.
>> 
>> Before starting all the work here, did you investigate alternatives
>> to this specific use of a tasklet? E.g., it being a softirq one, making
>> it have its own softirq?
> 
> If I understand you right, you mean implement an tasklet API that
> would only been be used by the hvm_do_IRQ_dpci? Its own spinlock,
> list, and an seperate tasklet_schedule?

No, just a new softirq type, e.g. HVM_DPCI_SOFTIRQ (added to
the enum in xen/include/xen/softirq.h and all the necessary
handling put in place).

Jan



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