Messages in this thread | | | Subject | Re: 2.6.xx: dirty pages never being sync'd to disk? | From | Arjan van de Ven <> | Date | Mon, 14 Nov 2005 16:35:49 +0100 |
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On Mon, 2005-11-14 at 10:30 -0500, Mark Lord wrote: > Okay, this one's been nagging me since I first began using 2.6.xx. > > My Notebook computer has 2GB of RAM, and the 2.6.xx kernel seems quite > happy to leave hundreds of MB of dirty unsync'd pages laying around > more or less indefinitely. This worries me, because that's a lot of data > to lose should the kernel crash (which it has once quite recently) > or the battery die. > > /proc/sys/vm/dirty_expire_centisecs = 3000 (30 seconds) > /proc/sys/vm/dirty_writeback_centisecs = 500 (5 seconds) > > My understanding (please correct if wrong) is that this means > that any (file data) page which is dirtied, should get flushed > back to disk after 30 seconds or so.
do you have laptop mode enabled? That changes the behavior bigtime in this regard and makes the kernel behave quite different.
also if these are files written to by mmap, the kernel only really sees those as dirty when the mapping gets taken down (eg the propagation from the pagetable dirty bit to the per page dirty bit goes a bit lazy)
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