Re: commit f6121f4f8708195e88cbdf8dd8d171b226b3f858 upstream

From: Jonathan Johnson
Date: Tue Oct 21 2008 - 10:22:19 EST

Hello all,

sched_rt.c: resch needed in rt_rq_enqueue() for the root rt_rq

commit f6121f4f8708195e88cbdf8dd8d171b226b3f858 upstream

Many previous kernels up to and include have had a "wa" time of 48-50% based on top or vmstat 1 100(last column heading, on the right).
After applying kernel the read "wa" time has dropped for reads down to 0%-10%. After reading the changelog
I used the same .config for this kernel as several previous ones.
I figured it must be this commit that made the different, since there are only about 12 commits and this seem most likely.


However, the "wa" times remain at 40%-50%(50% maybe 100% of one CPU core and its a dual) for writing and/or output. I don't know if there is a corresponding queue for writing or output,
but it also needs examining. I don't know how it related to reading from the hard drive either, but it was a dramatic improvement. Given that all on my hardware is almost "top-of-the-line", I
don't believe my hardware is at fault for the high "wa"(waiting for data).

My write speed especially to my RAID 6 seems to get worse and worse. I have all the same and supported hard drives. My original array had 6 mismatched drives at 20-24mb/s write speed.
I replaced them with 4 1TB drives and now write speed is under 100k/s especially when tranmitting data to this computer over the network.

I know some C++, but have never debug a program on this scale, and don't even know how to start. Any advice would be appreciated.


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