Messages in this thread | | | Date | Thu, 22 Mar 2007 07:41:44 -0400 | From | Bill Davidsen <> | Subject | Re: [PATCH 0/3] VM throttling: avoid blocking occasional writers |
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Tomoki Sekiyama wrote: > Hi, > > Thanks for your comments. > I'm sorry for my late reply. > > Bill Davidsen wrote: > > Andrew Morton wrote: > > >> - I wonder if dirty_limit_ratio is the best name we could choose. > >> vm_dirty_blocking_ratio, perhaps? Dunno. > >> > > I don't like it, but I dislike it less than "dirty_limit_ratio" I > guess. > > It would probably break things to change it now, including my > > sysctl.conf on a number of systems :-( > > I'm wondering which interface is preferred... > > 1) Just rename "dirty_limit_ratio" to "dirty_blocking_ratio." > Those who had been changing dirty_ratio should additionally modify > dirty_blocking_ratio in order to determine the upper limit of dirty > pages. > > 2) Change "dirty_ratio" to a vector, consists of 2 values; > {blocking ratio, writeback starting ratio}. > For example, to change the both values: > # echo 40 35 > /proc/sys/vm/dirty_ratio > And to change only the first one: > # echo 20 > /proc/sys/vm/dirty_ratio > In the latter way the writeback starting ratio is regarded as the > same as the > blocking ratio if the writeback starting ratio is smaller. And > then, the kernel behaves > similarly as the current kernel. > > 3) Use "dirty_ratio" as the blocking ratio. And add > "start_writeback_ratio", and start writeback at > start_writeback_ratio(default:90) * dirty_ratio / 100 [%]. > In this way, specifying blocking ratio can be done in the same way as > current kernel, but high/low watermark algorithm is enabled. I like 3 better, it should make tuning behavior more precise. You can make an argument for absolute values for writeback, if my disk will only write 70MB/s I may only want 203 sec of pending writes, regardless of available memory.
-- bill davidsen <davidsen@tmr.com> CTO TMR Associates, Inc Doing interesting things with small computers since 1979
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