> On Fri, 6 Aug 2010 09:18:59 +0900 (JST) > KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > > > > On Thu, Aug 5, 2010 at 4:56 PM, KOSAKI Motohiro > > > <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > > > > /proc/vmstat already have both. > > > > > > > > cat /proc/vmstat |grep nr_dirty > > > > cat /proc/vmstat |grep nr_writeback > > > > > > > > Also, /sys/devices/system/node/node0/meminfo show per-node stat. > > > > > > > > Perhaps, I'm missing your point. > > > > > > These only show the number of dirty pages present in the system at the > > > point they are queried. > > > The counter I am trying to add are increasing over time. They allow > > > developers to see rates of pages being dirtied and entering writeback. > > > Which is very helpful. > > > > Usually administrators get the data two times and subtract them. Isn't it sufficient? > > > > Nope. The existing nr_dirty is "number of pages dirtied since boot" > minus "number of pages cleaned since boot". If you do the > wait-one-second-then-subtract thing on nr_dirty, the result is > dirtying-bandwidth minus cleaning-bandwidth, and can't be used to > determine dirtying-bandwidth. Technically, yes. I meant, _now_, typical administrators are using the subtraction. Do you mean this is wrong? or do you mean you have another use case? Just curious. > I can see that a graph of dirtying events versus time could be an > interesting thing. I don't see how it could be obtained using the > existing instrumentation. tracepoints, probably.. I think it depend on frequency of the usecase. If the usecase is enouth major, convenience way (e.g. /proc/vmstat) is very helpful. probably, I haven't understand the usecase of this feature. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
