Messages in this thread | | | Date | Fri, 15 Jan 1999 22:07:27 +0000 | From | Jamie Lokier <> | Subject | Scheduling/nfs? problem with 2.2.0-pre7 |
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x11amp turns on a real-time scheduling mode when run as root, so that the music doesn't skip no matter what the computer load. Of course, it can do nothing about I/O load, but it reads ahead a little to make up for that.
I was using x11amp with 2.2.0-pre4 and it worked well. With 2.2.0-pre7, it is skipping quite regularly.
In both cases, the .mp3 files being played are on another system running 2.0.36, over a local ethernet (100base-T crossover cable).
Examining the network traffic, the skips happen when x11amp is reading some more data from a file. An NFS read request goes out; a reply comes back; another request goes out; a reply comes back. Normally, another request goes out, but when there's a skip, the third request is delayed by about 0.6 seconds. Note: the response from the server is always received very quickly, that is not the problem.
The timestamps on those packets show the NFS transactions are each taking one or two milliseconds normally.
strace output of the primary x11amp process, which reads from the .mp3 file, shows `read' being called during a skip and approx 0.6 seconds delay before the call returns.
The 0.6 second delay only happens with 2.2.0-pre7, not 2.2.0-pre4.
The delays seem to be triggered more often when I am typing. I.e., I press a key, and there is often a delay at the same time. I may be mistaken though -- it may be just coincidence. Of course, key presses often trigger other processing such as stuff being drawn on the screen by the X server etc. Still, it shouldn't be stalling NFS I/O.
Any ideas?
-- Jamie
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