On Sun, 26 Aug 2012 13:58:11 +0900 Carsten Haitzler (The Rasterman) <ras...@rasterman.com> wrote:
> On Sun, 26 Aug 2012 05:25:29 +0200 thomasg <tho...@gstaedtner.net> > said: > > i agree that a user should almost never switch frequencies by hand > this is rather pointless. cpufreq allows it - but it's there for > tweakers (like me) so i can even measure power usage at various > freqs, performance etc. it's buried inside a menu so as not to be too > convenient. > > imho all we need to do from userspace is switch governors or tweak > them. that means right now powersave / automatic / ondemand / > performance. these governors do not HAVE to keep the cpu at min or > max freq. they happen to with powersave and performance, but > conceptually they could switch frequencies around. if performance can > clock down and be done totally imperceptible to benchmarking, the ui > and responsiveness, then why not? but it doesn't. > > the reality that *I* see is that ondemand/automatic have visible > impacts to the user (other than the fan spinning up/down temperature > and power consumption changing). i literally can watch my compile > scrolling by faster switching to performance. its a big jump. it's > not a placebo effect. to prove the point here are numbers for "make > clean maintainer-clean; ./autogen.sh --disable-static && make -j10 && > sudo make -j10 install" for e17 on my machine: > > (this machine core i5 1.6ghz->3.4ghz, 8gb ram, x86_64, all data on > ssd so no hdd slowness, i ran the exact same compile before the first > run to ensure all caches are warmed up, linux 3.2.0) > > (maximum speed, automatic, low power automatic, minimum speed) > performance : 91 sec > ondemand : 122 sec > conservative: 113 sec > powersave : 198 sec > > ondemand/powersave are not invisible. it's not a placebo effect. i > have spent my life staring at graphics and animation and i can > sometimes SEE the difference with responsiveness just in frame > rendering when using these. i don't have a quick test to prove it but > i'm less likely to be affected by placebo as this is what i have done > for most of my life - stare at graphics, animation and spot single > pixel glitches and off-by-1's and incorrect frame timings. i'm > normally very sceptical so if i am seeing an effect, it probably is > very much there. i just don't have a test for you. i could try make > one... maybe measure time from ecore wakeup on event to time until > frame render done and flushed. > > believe it or not humans do perceive latencies of less than 20ms. you > just can't quite realize what you are perceiving and end up saying > "this thing is slow" when it's fast - it never drops a frame, but.. > it's just got higher latency. 20ms is enough to be 1 frame behind > (actually less is enough). when you get an event u want time from > event to result on screen to be as short as possible. this is because > events can come in at ANY time, BUT your screen is refreshing at a > constant fixed rate. higher latencies present themselves eg as > pointer being further ahead of the scrollbar or scrolling content or > window u are moving than normal. if you miss being able to get data > in at one frame, it has to be delayed until the next frame. this ADDS > (at 60hz) up to 16.66ms to your latency of display already. so here's > an example. > > 2ms before the next refresh you get an event. you respond and render. > this rendering take 4ms. oops. you missed the frame. so now your > update waits another 14.66ms from the time u finished rendering until > user sees it. total latency from input event to seeing result -> > 18.66ms. now to make it even worse, with compositing we have ANOTHER > rendering step - the compositor. so add some more ms to the rendering > time etc. etc. not to mention the slower your machine (eg cpu clocked > down or just old machine) the longer the rendering time and the more > often you end up in this bucket and the longer your latency. given > the right circumstances, if you are JUST fast enough to render frames > at screen refresh given your cpu power etc. then u can be UP to 33ms > behind the event that generated the redraw. this is visible > ESPECIALLY if dragging. And if you are doing 3D networked virtual world development like I do, add in another 320 ms of delay to the other side of the world to your responsiveness. I get 20 ms pings to my country, but it seems to add about 150 ms for each hop across major oceans, and my routes tend to go the long way. I blame Telstra, this is Australia, it's always safest to just blame Telstra. -- A big old stinking pile of genius that no one wants coz there are too many silver coated monkeys in the world. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ enlightenment-users mailing list enlightenment-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/enlightenment-users
