On Tuesday 23 October 2001 21:54, dave willis wrote: > i just finished testing several different patched and unpatched linux > kernels, and was surprised by the results: all basically the same. >
This is not surprising - the various low-latency patches only address latency issues on loaded systems. You should try running some other cpu or disk intensive processes at the same time to see the differences. Karl > alsa range = 33.4% to 33.8% 1.336 ms to 1.352 ms diff = 0.016 ms > oss-emu range = 91.6% to 91.9% 3.664 ms to 3.676 ms diff = 0.012 ms > > as you can see, the differences are negligible and probably irrelevant if > more tested were done, and a standard 2.4.12 kernel is just as good as any > patched kernel. > > one note: when i did a real-world test of latency by looping a signal > through my card and dividing the difference in time by 2 (because of input > and output latency), i got 3.675 ms latency using kernel 2.4.8-ll with oct > 1 alsa-cvs, and that corresponds with the oss-emu latency for some reason > instead of the alsa latency. i don't know why, and i'll test this on > other kernels soon. > > my system is an amd athlon 900 mhz running at 1006 mhz with redhat 7.1 and > an m-audio delta audiophile 2496 soundcard. i used alsa-cvs from october > 20 and takashi iwai's modified version of latencytest0.42+alsa. the > kernels tested are 2.4.8-ll, 2.4.9-ll, 2.4.10-ll, 2.4.10-pe, 2.4.12, > 2.4.12-ac2, 2.4.12-ac2-ll, 2.4.12-ac3, and 2.4.12-ac3-pe. > ll = low-latency > pe = pre-emptive > ac2 and ac3 are alan cox's patches > > latencytest was ran as follows: > ./latencytest -t alsa -d hw -q none 3 256 > ./latencytest -t oss -q none 3 256 > > -dave > > details below: > ----------------------------------------------------------------------- > sample rate = 48000 > NUMBER of OVERRUNS = 0 PIXEL_PER_MS=112 > fragment latency = 1.333333 ms buffer latency= 4.000 ms > fragment size=256 total buffer size=768 > cpu_load= 80.0000% cpu latency = 1.066667 ms > with alsa, 100% of samples are within 1ms of buffer > used alsa-cvs from oct 20, oss = alsa's oss-emu > > ====================2.4.10-ll==================== > output type = ALSA max latency=1.3 ms factor=33.4 % of buffer > > output type = OSS max latency=3.7 ms factor=91.6 % of buffer > 1MS factor=83.467993 2MS factor=99.937850 > > ====================2.4.10-pe==================== > output type = OSS max latency=3.7 ms factor=91.9 % of buffer > 1MS factor=83.367698 2MS factor=99.965636 > > output type = ALSA max latency=1.3 ms factor=33.6 % of buffer > > ====================2.4.12-ac2-ll==================== > output type = ALSA max latency=1.3 ms factor=33.7 % of buffer > > output type = OSS max latency=3.7 ms factor=91.7 % of buffer > 1MS factor=83.400810 2MS factor=99.932524 > > ====================2.4.12-ac2==================== > output type = ALSA max latency=1.3 ms factor=33.4 % of buffer > > output type = OSS max latency=3.7 ms factor=91.7 % of buffer > 1MS factor=83.372922 2MS factor=99.966067 > > ====================2.4.12-ac3==================== > output type = ALSA max latency=1.4 ms factor=33.8 % of buffer > > output type = OSS max latency=3.7 ms factor=91.7 % of buffer > 1MS factor=83.361392 2MS factor=99.971942 > > ====================2.4.12-ac3-pe==================== > output type = ALSA max latency=1.3 ms factor=33.5 % of buffer > > output type = OSS max latency=3.7 ms factor=91.7 % of buffer > 1MS factor=83.390216 2MS factor=99.943117 > > ====================2.4.12==================== > output type = ALSA max latency=1.3 ms factor=33.4 % of buffer > > output type = OSS max latency=3.7 ms factor=91.7 % of buffer > 1MS factor=83.372828 2MS factor=99.960506 > > ====================2.4.8-ll==================== > output type = ALSA max latency=1.3 ms factor=33.6 % of buffer > > output type = OSS max latency=3.7 ms factor=91.6 % of buffer > 1MS factor=83.402836 2MS factor=99.972199 > ====================2.4.9-ll==================== > output type = ALSA max latency=1.3 ms factor=33.4 % of buffer > > output type = OSS max latency=3.7 ms factor=91.7 % of buffer > 1MS factor=83.385093 2MS factor=99.948240 > > > > _______________________________________________ > Alsa-devel mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/alsa-devel _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
