Messages in this thread | | | Subject | Re: scheduler vs hardware? (was Re: another i7 (linux) bug?) | From | Peter Zijlstra <> | Date | Fri, 22 Jan 2010 09:51:12 +0100 |
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On Fri, 2010-01-22 at 08:19 +0100, Mike Galbraith wrote: > > if I run a cpu intensive process with the lowest priority (19 > > from man nice) I obtain much better performance that with the > > highest priority available (-20 from man nice). > > > > For example the same file is processed by lame in 8.7 seconds > > at the lowest priority, and in 12 seconds at the highest > > priority. Before posting a bug I wold like to understand if > > this is a problem related to the i7 mobile (my processor is a > > i7 Q720). > > > > As far as I tested on the same laptop series (dell studio 15), > > with the same kernel this problem does not exists. > > So you only see this on the i7. That's odd. Can you try 33-rc5? > > Posting a reliable reproducer would be nice. It'd also be nice to see > what all is running when you see this, and where.
Using a sample from: http://lame.sourceforge.net/quality.php
My laptop does:
# time nice -n 19 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null LAME 3.98.2 64bits (http://www.mp3dev.org/) Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz Encoding youcantdothat.wav to <stdout> Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=0) Frame | CPU time/estim | REAL time/estim | play/CPU | ETA 1147/1147 (100%)| 0:03/ 0:03| 0:03/ 0:03| 9.3341x| 0:00 32 [ 1] * 256 [1009] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 320 [ 137] %%%%%%%%% ---------------------------------------------------------------------------- kbps LR MS % long switch short % 263.4 99.1 0.9 90.5 5.5 4.0
real 0m3.273s user 0m3.217s sys 0m0.022s
# time nice -n 0 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null LAME 3.98.2 64bits (http://www.mp3dev.org/) Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz Encoding youcantdothat.wav to <stdout> Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=0) Frame | CPU time/estim | REAL time/estim | play/CPU | ETA 1147/1147 (100%)| 0:01/ 0:01| 0:01/ 0:01| 27.239x| 0:00 32 [ 1] * 256 [1009] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 320 [ 137] %%%%%%%%% ---------------------------------------------------------------------------- kbps LR MS % long switch short % 263.4 99.1 0.9 90.5 5.5 4.0
real 0m1.121s user 0m1.102s sys 0m0.013s
# time nice -n -20 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null LAME 3.98.2 64bits (http://www.mp3dev.org/) Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz Encoding youcantdothat.wav to <stdout> Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=0) Frame | CPU time/estim | REAL time/estim | play/CPU | ETA 1147/1147 (100%)| 0:01/ 0:01| 0:01/ 0:01| 27.239x| 0:00 32 [ 1] * 256 [1009] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 320 [ 137] %%%%%%%%% ---------------------------------------------------------------------------- kbps LR MS % long switch short % 263.4 99.1 0.9 90.5 5.5 4.0
real 0m1.112s user 0m1.093s sys 0m0.018s
On a Nehalem class server machine it does:
# time nice -n 19 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null LAME 3.98.2 64bits (http://www.mp3dev.org/) Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz Encoding youcantdothat.wav to <stdout> Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=0) Frame | CPU time/estim | REAL time/estim | play/CPU | ETA 1147/1147 (100%)| 0:00/ 0:00| 0:00/ 0:00| 32.926x| 0:00 32 [ 1] * 256 [1009] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 320 [ 137] %%%%%%%%% ---------------------------------------------------------------------------- kbps LR MS % long switch short % 263.4 99.1 0.9 90.5 5.5 4.0
real 0m0.932s user 0m0.917s sys 0m0.005s
# time nice -n 0 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null LAME 3.98.2 64bits (http://www.mp3dev.org/) Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz Encoding youcantdothat.wav to <stdout> Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=0) Frame | CPU time/estim | REAL time/estim | play/CPU | ETA 1147/1147 (100%)| 0:00/ 0:00| 0:00/ 0:00| 32.568x| 0:00 32 [ 1] * 256 [1009] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 320 [ 137] %%%%%%%%% ---------------------------------------------------------------------------- kbps LR MS % long switch short % 263.4 99.1 0.9 90.5 5.5 4.0
real 0m0.927s user 0m0.922s sys 0m0.003s
# time nice -n -20 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null LAME 3.98.2 64bits (http://www.mp3dev.org/) Using polyphase lowpass filter, transition band: 19383 Hz - 19916 Hz Encoding youcantdothat.wav to <stdout> Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=0) Frame | CPU time/estim | REAL time/estim | play/CPU | ETA 1147/1147 (100%)| 0:00/ 0:00| 0:00/ 0:00| 32.926x| 0:00 32 [ 1] * 256 [1009] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 320 [ 137] %%%%%%%%% ---------------------------------------------------------------------------- kbps LR MS % long switch short % 263.4 99.1 0.9 90.5 5.5 4.0
real 0m0.919s user 0m0.914s sys 0m0.005s
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