Am 20.03.2013 um 16:41 schrieb Arvid Brodin: > On 2013-03-20 00:20, Arvid Brodin wrote: >> Hello, >> >> Just out of curiosity, I wrote this program to test the latency using a >> vanilla 3.4 kernel's "real-time scheduler". Maybe it is of interest to >> someone on this list. >> > > I just ran this on a Gentoo system with a radeon card, running linux-3.4 > and an up-to-date user space. Although in general the latencies were > much lower running under SCHED_FIFO, I still got latencies up to almost > 2000 µs while browsing the web. So not very usable...
it's not necessarily the scheduler all tricks of the trade, and rules of reducing latency still apply - just because you're running on a vanilla kernel you cant skimp on that ;) try booting with the 'idle=poll' or 'nohlt' option and see what changes (and feel the room temperature rising ;) there are sources of latency like recovery from idle/powersave states which regulate down the onboard SMPS for the CPU; that needs time to get back up to full speed voltage given the large bypass capacitors; also some clock generation might go through a phase-locked loop and that wont kick into high gear instantaneous either - Michael here's an intro to every trick hardware manufacturers came up with over time wrt power saving states: http://www.hardwaresecrets.com/article/Everything-You-Need-to-Know-About-the-CPU-C-States-Power-Saving-Modes/611/2 > The first system I ran the test on (and which got latencies in the +/-80 > µs range) was an Intel Core i3 with Intel HD graphics. > > -- > Arvid > > ------------------------------------------------------------------------------ > Everyone hates slow websites. So do we. > Make your web apps faster with AppDynamics > Download AppDynamics Lite for free today: > http://p.sf.net/sfu/appdyn_d2d_mar > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_mar _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
