BY: adamwu
DATE: 2007-Jul-25 19:48
SUBJECT: Network performance downgrade in 2.4.17After many trial and error, I finally got 2.4.17 up and running on my PSTwo.
I noticed a message as soon as smap is loaded, saying dma setup error, go back to PIO mode. The network still funcions.
However, when I try ftp, I found out the throughput is not as good as in kernel 2.2.1.
pc -> ps2 was 3MB/sec, now 1.5MB/sec
ps2 -> pc was 4MB/sec, now 1.5MB/sec
Upon further inspection, I found the network performance is heavily CPU-bound: at 1.5MB/sec, smap used about 50% cpu time, and the rest is spent in tcpd (ftp server).
I have not checked the CPU usage in kernel 2.2.1, will do that later.
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I have a few guesses.
The first hint is the dma error message. However, I believe smap is not using dma back in kernel 2.2.1, either;
Then the high CPU usage gave another hint - the system is being hit by heavy interrupt. I think it is because I did not enable I2O when compiling (last time I used it and the kernel did not boot up completely). I will try another clean compile with I2O on and see how it runs. |
Network performance downgrade in 2.4.17