[linux-audio-dev] disk latency under 2.4.19 ll+preempt

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Subject: [linux-audio-dev] disk latency under 2.4.19 ll+preempt
From: jfm3 (jfm3_AT_ouroboros-complex.org)
Date: Tue Nov 19 2002 - 22:29:19 EET

I'm running the low latency and preemption kernel patches on 2.4.19. I'm
getting disk copy latency of around 10ms. Since I'm a real time person
(according to M. Goggins) who doesn't use the hd in real time, I can
live with this, but it bugs me. I've tried ext2 and ext3, no difference.
Any other tips?

(Tue Nov 19 15:20:19)
(root_AT_head:/home/jfm3/latencytest/latencytest0.42-png)
bash> ./do_tests none 3 256 0 350000000
x11perf - X11 performance program, version 1.5
The XFree86 Project, Inc server version 40200000 on :0.0
from head
Tue Nov 19 15:20:32 2002

Sync time adjustment is 0.2320 msecs.

   2000 reps @ 3.8063 msec ( 263.0/sec): Scroll 500x500 pixels
   2000 reps @ 3.8071 msec ( 263.0/sec): Scroll 500x500 pixels
   2000 reps @ 3.8092 msec ( 263.0/sec): Scroll 500x500 pixels
   2000 reps @ 3.8064 msec ( 263.0/sec): Scroll 500x500 pixels
   2000 reps @ 3.8187 msec ( 262.0/sec): Scroll 500x500 pixels
  10000 trep @ 3.8095 msec ( 262.0/sec): Scroll 500x500 pixels

    120 reps @ 52.5438 msec ( 19.0/sec): ShmPutImage 500x500 square
    120 reps @ 52.7976 msec ( 18.9/sec): ShmPutImage 500x500 square
    120 reps @ 52.9418 msec ( 18.9/sec): ShmPutImage 500x500 square
    120 reps @ 52.8095 msec ( 18.9/sec): ShmPutImage 500x500 square
    120 reps @ 52.8810 msec ( 18.9/sec): ShmPutImage 500x500 square
    600 trep @ 52.7948 msec ( 18.9/sec): ShmPutImage 500x500 square

fragment latency = 1.451247 ms
cpu latency = 1.160998 ms
  2.1ms ( 0)|
1MS num_time_samples=57348 num_times_within_1ms=57348 factor=100.000000
2MS num_time_samples=57348 num_times_within_2ms=57348 factor=100.000000
PIXEL_PER_MS=155
fragment latency = 1.451247 ms
cpu latency = 1.160998 ms
  2.0ms ( 0)|
1MS num_time_samples=20877 num_times_within_1ms=20877 factor=100.000000
2MS num_time_samples=20877 num_times_within_2ms=20877 factor=100.000000
PIXEL_PER_MS=155
fragment latency = 1.451247 ms
cpu latency = 1.160998 ms
  4.6ms ( 2)|
1MS num_time_samples=28116 num_times_within_1ms=28113 factor=99.989330
2MS num_time_samples=28116 num_times_within_2ms=28115 factor=99.996443
PIXEL_PER_MS=155
-rw-r--r-- 1 root root 350000000 Nov 19 15:23 tmpfile
fragment latency = 1.451247 ms
cpu latency = 1.160998 ms
  6.9ms ( 44)|
1MS num_time_samples=68188 num_times_within_1ms=68144 factor=99.935473
2MS num_time_samples=68188 num_times_within_2ms=68144 factor=99.935473
PIXEL_PER_MS=155
-rw-r--r-- 1 root root 350000000 Nov 19 15:23 tmpfile
-rw-r--r-- 1 root root 350000000 Nov 19 15:25 tmpfile2
fragment latency = 1.451247 ms
cpu latency = 1.160998 ms
  6.5ms ( 8)|
1MS num_time_samples=54930 num_times_within_1ms=54921 factor=99.983616
2MS num_time_samples=54930 num_times_within_2ms=54923 factor=99.987257
PIXEL_PER_MS=155
-rw-r--r-- 1 root root 350000000 Nov 19 15:23 tmpfile
-rw-r--r-- 1 root root 350000000 Nov 19 15:25 tmpfile2 

-- 
(jfm3  2838 BCBA 93BA 3058 ED95  A42C 37DB 66D1 B43C 9FD0)

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