Joern Nettingsmeier wrote: > > some new interesting results with 2.5.42: > > http://spunk.dnsalias.org/latencytest/2.5.42/2x256.html > > overall much worse, *but* greatly reduced latency peaks (max. 6 ms) as > compared to 2.5.41: > > http://spunk.dnsalias.org/latencytest/2.5.41/2x256.html > > here the peaks easily reach 13 ms.
Rather depends on the filesystem. ext3 does its own write scheduling, and does stuff inside lock_kernel(). It needs a couple of scheduling points I guess. I'd expect ext2 to work OK with preemption, but nobody has really looked yet. Unless you're using ftruncate() (grr.) > i'm not really sure what to make of this.... > can someone explain ? > > andrew, it seems part of your mm patch was merged - is there an updated > patch around that will add the missing hunks ? Well 2.5.41 had the big change to the truncate code, which was a rather important part of this whole effort. I can't immediately think of a 2.5.42 change which would do this... But nobody has really got down and dug out the toolkit on 2.5 scheduling latency. I guess I should do that soon.
