Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods
Date	2017-07-18 21:00 +0200
Message-ID	<u4FSW-61V-23@gated-at.bofh.it> (permalink)
References	(5 earlier) <u3bay-5vu-17@gated-at.bofh.it> <u3bke-5Oq-9@gated-at.bofh.it> <u3bDA-5W4-11@gated-at.bofh.it> <u4jSq-Gx-31@gated-at.bofh.it> <u4kbN-Pt-51@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Mon, Jul 17, 2017 at 12:48:38PM -0700, Arjan van de Ven wrote:
> On 7/17/2017 12:23 PM, Peter Zijlstra wrote:
> > Of course, this all assumes a Gaussian distribution to begin with, if we
> > get bimodal (or worse) distributions we can still get it wrong. To fix
> > that, we'd need to do something better than what we currently have.
> > 
> 
> fwiw some time ago I made a chart for predicted vs actual so you can sort
> of judge the distribution of things visually
> 
> http://git.fenrus.org/tmp/linux2.png

That shows we get it wrong a lot of times (about 50%, as per the
average) and moving the line has benefit. Since for performance you
really don't want to pick the deeper idle state, so you want to bias
your pick towards a shallower state.

Using the CDF approach you can quantify by how much you want it moved.

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-18 21:00 +0200

csiph-web