On 07/26/2015 09:14 PM, Davidlohr Bueso wrote:
On Wed, 2015-07-22 at 16:12 -0400, Waiman Long wrote:
This patch enables the accumulation of kicking and waiting related
PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration
option is selected. It also enables the collection of kicking and
wakeup latencies which have a heavy dependency on the CPUs being used.
The measured latencies for different CPUs are:
CPU Wakeup Kicking
--- ------ -------
Haswell-EX 89.8us 7.4us
Westmere-EX 67.6us 9.3us
But you don't mention anything about the overhead of enabling
QUEUED_LOCK_STAT. This does several atomic ops, thus potentially
thrashing workloads.
Yes, QUEUED_LOCK_STAT will slow performance a bit. It is like enabling
LOCK_STAT and you will expect some slow down too. It is essentially a
debugging option to see what had actually happened in the system. It
should be turned off in a production system.
Cheers,
Longman
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
