Re: What causes iowait other than waiting for i/o?

[Rik van Riel]

Bill Davidsen wrote:
> I recently noted that my system was spending a lot of time in i/o wait 
> when doing some tasks which I thought didn't involve i/o, as noted by 
> the lack of disk light activity most of the time. I thought of network, 
> certainly the NIC had no activity for this job. So I set up a little 
> loop to capture all disk i/o and network activity (including loopback). 
> That was no obvious help, and the program doesn't use pipes.
>
> At this point I'm really curious, does someone have a good clue?
>
> Note: I don't think this is a bug or performance issue, unless the 
> kernel is doing something and charging time to iowait instead of system 
> I don't see anything to fix, but I would like to understand.

All filesystem IO and direct disk IO can cause iowait.

This includes NFS activity.

--
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/