> > I'm only testing on a desktop with 2 drives. I use a simple test to > > write 2gb to sda then 2gb to sdb while recording the threshold values. > > On 2.6.39-rc3, after the 2nd write starts it take approx 90 seconds for > > sda's threshold value to drop from its maximum to minimum and sdb's to > > rise from min to max. So this seems much too slow for normal desktop > > workloads. > > Yes. > > > I haven't tested with this patch on 2.6.39-rc3 yet, but I'm just about > > to set that up. > > It will sure help, but the problem is now the low-memory NAS servers.. > > Fortunately my patchset could make the dirty pages ramp up much more > fast than the ramp up speed of the per-bdi threshold, and is also less > sensitive to the fluctuations of per-bdi thresholds in JBOD setup. Look at the attached graph. You cannot notice an obvious "rampup" stage in the number of dirty pages (red line) at all :) Thanks, Fengguang
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