Messages in this thread | | | Date | Tue, 2 Nov 2010 09:20:06 +0800 | From | Wu Fengguang <> | Subject | Re: 2.6.36 io bring the system to its knees |
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On Mon, Nov 01, 2010 at 01:09:34AM +0000, Dimitrios Apostolou wrote: > Hello, > > On Sun, 31 Oct 2010 09:51:32 +0800, Wu Fengguang wrote: > > It may also help to lower the dirty ratio. > > > > echo 5 > /proc/sys/vm/dirty_ratio > > > > Memory pressure + heavy write can easily hurt responsiveness. > > > > - eats up to 20% (the default value for dirty_ratio) memory with dirty > > pages and hence increase the memory pressure and number of swap IO > > My experience has been different with that. Wouldn't it make more sense > to _increase_ dirty_ratio (to 50 lets say) and at the same time decrease > dirty_background_ratio? That way writing to disk starts early, but the > related apps stall waiting for I/O only when dirty_ratio is reached.
50% dirty ratio may help before the system goes thrashing (writing processes will be throttled less/later). However Aidar is seeing hours of unresponsiveness with heavy IO, in this case large dirty ratio won't help reduce the throttling any more.
Thanks, Fengguang
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