locks and kernel randomness...

[Alfred Perlstein]

On 2/25/15 3:56 AM, Konstantin Belousov wrote:

> The cost of the proposed patch, of course, is not the several
> thousands of instructions in the rebalance. The problem with it is the
> introduction of the new spinlock, which will be used in many places
> after the introduction. The cost of the new and often used spinlock is
> the increase of both interrupt latency and interrupt handler jitter and
> cpu switch jitter.
>
> So neither buildworld timing, nor network throughput are adequate
> to estimate the change.  It is system unresponsivness and loss of
> the realtime behaviour up to some degree.
>
> I thought that it was obvious, at least after spinlocks were mentioned,
> but apparently it is not, since proposals to measure the patch effect
> by benchmarking buildworld or passing the traffic are made.
>

Thank you.

-Alfred