Messages in this thread | | | Subject | Re: nfs unhappiness with memory pressure | From | Trond Myklebust <> | Date | Mon, 05 Dec 2005 19:48:19 -0500 |
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On Tue, 2005-12-06 at 10:40 +1100, Nick Piggin wrote:
> > ...and most important of all: 'unstable' does _not_ mean that I/O is > > active on those pages (unlike the apparent assumption in > > vm_throttle_write. > > That is why the choice is either to kick pdflush there, or to remove > > nr_unstable from the accounting in that loop. > > > > Doesn't matter if IO is actually active or not, if you've allocated > memory for these unstable pages, then page reclaim can scan itself > to death, which is what seems to have happened here. And which is > what vm_throttle_write is supposed to help.
Unless someone somehow triggers an NFS commit, then nr_unstable is not ever going to decrease, and your process will end up looping forever. In fact, those nr_writeback that refer to NFS pages, will end up being added to nr_unstable (because they have been written to the server, but not committed to disk).
Cheers, Trond
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