Re: debug a high load average

[Rajesh <rvarada@gmail.com>]

Erik Mouw wrote:

>On Tue, Aug 23, 2005 at 04:38:36PM +0530, Rajesh wrote:
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>>I have a case occasionally when I copy data from a usb storage (ipod) to 
>>my hard drive the load average goes up from 0.4 to about 15.0, and the 
>>system becomes very unusable till I kill the cp command. I have checked 
>>the CPU usage, bytes read from usb device, byte written to hard drive 
>>etc, and all these values are low like CPU usage is at a maximum of 30%, 
>>disk read bytes is at an average of 1.5 MiB/s, disk write bytes is at 
>>1.5 MiB/s, number of processes is at 110, etc, during this high load.
>>    
>>
>
>1.5 MB/s suggests you're using an IDE drive in PIO mode. Switch to DMA
>mode (hdparm -d 1 /dev/hda) and see if it gets any better.
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It seems to have helped a little. Now the rate at which load average 
goes up has decreased ( I can copy up to about 700-800 MiB compared to a 
high of 200MiB earlier), but it is still going up to 15 gradually at 
which point I am still killing the cp process to make the system usable.

I know I am not giving much information. But if I know what factors 
cause the loadavg to keep on going up I will gladly provide it.

I am running  2.6.12 kernel on a laptop. I have an ipod attached to my 
USB 1.1 as a drive on which I am saving and retreiving large 
files(2-4GiB files). The transfer speed is slow, but I am fine with it, 
as long as the load average stays within bounds so that the machine is 
usable. (If I dual boot to windows and do the same operation, I am able 
to get the files copied over in a few minutes.). Can vfat be a factor?

Thanks
Rajesh

>Erik
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