On Fri, Oct 21, 2011 at 12:05:30AM +0800, Wu Fengguang wrote:
> Trond,
> 
> After applying these two patches, the IO-less patchset performances
> 45% better than the vanilla kernel and the average commit size only
> decreases by -16% in the common NFS-thresh=1G/nfs-1dd case :)

To better understand how the NFS writeback wait queue helps, I
visualized the network traffic over time. Attached are the graphs for
the vanilla kernel and the one with the IO-less + NFS wait queue
patches.

nfs-1dd-4k-32p-32016M-1024M:10-3.1.0-rc8-vanilla+/dstat-bw.png
nfs-1dd-4k-32p-31951M-1024M:10-3.1.0-rc8-nfs-wq4+/dstat-bw.png

The obvious difference is, the network traffic become now more
distributed and the "zero traffic" periods are mostly reduced.

The other 2dd, 10dd cases have similar results.

Thanks,
Fengguang