Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 13 Sep 2006 12:32:41 +1000 | From | Nick Piggin <> | Subject | Re: [2.6.17.4] slabinfo.buffer_head increases |
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Guennadi Liakhovetski wrote: > On Tue, 12 Sep 2006, Nick Piggin wrote: > >> Guennadi Liakhovetski wrote: >> >>>> On Mon, 10 Jul 2006, Guennadi Liakhovetski wrote: >>>> >>>>> I am obsering a steadily increasing buffer_head value in slabinfo >>>>> under >>>>> 2.6.17.4. I searched the net / archives and didn't find anything >>>>> directly relevant. Does anyone have an idea or how shall we debug it? >>>> >>>> >>> >>> The problem is still there under 2.6.18-rc2. I narrowed it down to >>> ext3 journal. To reproduce one just has to mount an ext3 partition >>> and perform (write) accesses to it. A loop { touch /mnt/foo; sleep 1; >>> } suffices - just let it run for a couple of minutes and monitor >>> buffer_head in /proc/slabinfo. If you mount it as ext2 the problem is >>> gone. >> >> >> >> What data mode is ext3 mounted with? > > > Default, i.e., ordered, I guess. > >> Is the memory reclaimable? If yes, is it a problem? > > > Yes, that's why I later wrote that the problem is not real. It was hard > to see as we had a lot of free RAM on the system, the system was idle > apart from one script that only did "touch x" periodically with the same > "x" and the buffer_head slab was growing very steadily. Unlike with ext2 > / reiserfs. That's why I decided it was not ok. But the memory is > reclaimable, so, seems like not a problem. Just a bit odd that such a > "harmless" operation causes a steady growth of buffer_heads...
OK. It is just a quirk in the way that ext3 ordered interacts with page freeing and reclaim, I think. If it is causing you no performance problems then that's good. Though it is counter intuitive.
Thanks for the report anyway.
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