Lock profiling results on TCP and an 8.x project
Robert Watson
rwatson at FreeBSD.org
Sun Oct 21 06:00:03 PDT 2007
On Sat, 20 Oct 2007, Robert Watson wrote:
> * When talking about percentage of available CPUs, I make the assumption
> that
> due to a sufficient quantity of CPUs, in most cases lock acquisition will
> occur as a result of adaptive spinning rather than sleeping. In the
> netperf
> case, this is not true, since the number of potential workers exceeds the
> number of CPUs, hence the turnstile contention. However, as sleeping on
> locks itself is very expensive, it's reasonable to assume we would recover
> a lot of CPU none-the-less.
FYI, a feature request for lock profiling: it would be nice if we also tracked
for each contention point time spent spinning vs. context switched waiting for
the lock, and the number of context switches the lock acquisition point has
caused. This would allow us to better understand the impact of adaptive lock
behavior for workloads and configurations.
Robert N M Watson
Computer Laboratory
University of Cambridge
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