Re: [PATCH 2/3] x86: Implement prctl PR_GET_TSC and PR_SET_TSC

[Erik Bosman]

On Sat, 12 Apr 2008, H. Peter Anvin wrote:

>
> I also saw no mention about performance impact, which need to be
> considered whenever *anything* is proposed to be inserted into a hot
> path.  It may be (heck, *should be*) that the performance impact isn't
> measurable, but that needs to be positively established.
>
> 	-hpa
>

It took me a while, but I have done some tests om my system with and
without my patch applied.

All deamons but klogd/syslogd were shut down andI used the following
command:

LMBENCH_SCHED="SINGLE" \
/usr/lib/lmbench/bin/{i686-pc,x86_64}-linux-gnu/lat_ctx -s 0 2

The variation was quite high so I ran it a 1000 times for each
configuration.

x86_32, patch applied,     1000x repeated, avg: 1.319, rmse: 0.081
x86_32, patch not applied, 1000x repeated, avg: 1.335, rmse: 0.107

x86_64, patch applied,     1000x repeated, avg: 1.417, rmse: 0.0716
x86_64, patch not applied, 1000x repeated, avg: 1.423, rmse: 0.0745

This is on a core 2 duo E6300.

Erik
--
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/