On Wed, May 12, 2010 at 1:46 AM, James Cameron <[email protected]> wrote: > With the 250Mb test I've been doing, this causes 8 seconds in dd, 147 > seconds in sync, and a nice distribution of write latencies (largest > samples 0.2s 0.1s 44ms 15ms 8ms, median 85us, smallest sample 80us).
Great! Must say that dirty_ratio=90 seems high -- default is 20, which is 20% of available memory. I think your settings look like vm.dirty_background_ratio=10 vm.dirty_expire_centisecs=60000 vm.dirty_ratio=90 vm.dirty_writeback_centisecs=0 can you test with vm.dirty_writeback_centisecs=100 # frequent pdflush process wakeups vm.dirty_expire_centisecs=500 # make data qualify for pdflush earlier vm.dirty_background_ratio=10 # pdflush should start working early vm.dirty_ratio=30 # or maybe 40 -- this is the backstop this should kickoff a background writer early, and make data "ripe" for it to flush early too. The downside here is that a low dirty_writeback_centisecs generates kernel wakeups. Those wakeups can be liberally skipped when the system is clearly idle -- but I doubt there is currently a dynamic test for that... > Oh I wish I had a storage activity LED on internal SD. ;-) Perhaps iotop helps without disturbing the results too much? cheers, m -- [email protected] [email protected] -- School Server Architect - ask interesting questions - don't get distracted with shiny stuff - working code first - http://wiki.laptop.org/go/User:Martinlanghoff _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
