Re: [PATCH] smp, ipi: Speed up IPI handling by invoking the callbacks in reverse order

[Srivatsa S. Bhat]

On 06/05/2014 01:17 AM, Peter Zijlstra wrote:
> On Thu, Jun 05, 2014 at 01:09:35AM +0530, Srivatsa S. Bhat wrote:
>> The current implementation of lockless list (llist) has a drawback: if we
>> want to traverse the list in FIFO order (oldest to newest), we need to
>> reverse the list first (and this can be expensive if the list is large,
>> since this is an O(n) operation).
> 
> Have you actually looked at the queue depth of this thing? Large queues
> are a problem for interrupt latency.
> 

Actually, I wrote this patch just by looking at the code and realizing
that we don't need to reverse the list. In practice, I haven't actually
seen any noticeable interrupt latencies or large queues so far. So I think
this patch is just a very tiny optimization, that's all.

Regards,
Srivatsa S. Bhat

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/