On Tue, May 17, 2011 at 08:51:47AM -0500, Christoph Lameter wrote: > On Tue, 17 May 2011, Mel Gorman wrote: > > > entirely. Christoph wants to maintain historic behaviour of SLUB to > > maximise the number of high-order pages it uses and at the end of the > > day, which option performs better depends entirely on the workload > > and machine configuration. > > That is not what I meant. I would like more higher order allocations to > succeed. That does not mean that slubs allocation methods and flags passed > have to stay the same. You can change the slub behavior if it helps. > In this particular patch, the success rate for high order allocations would likely decrease in low memory conditions albeit the latency when calling the page allocator will be lower and the disruption to the system will be less (no copying or reclaim of pages). My expectation would be that it's cheaper for SLUB to fall back than compact memory or reclaim pages even if this means a slab page is smaller until more memory is free. However, if the "goodness" criteria is high order allocation success rate, the patch shouldn't be merged. > I am just suspicious of compaction. If these mods are needed to reduce the > amount of higher order pages then compaction does not have the > beneficial effect that it should have. It does not actually > increase the available higher order pages. Fix that first. > The problem being addressed was the machine being hung at worst and in other cases having kswapd pinned at 99-100% CPU. It's now been shown that modifying SLUB is not necessary to fix this because the bug was in page reclaim. The high-order allocation success rate didn't come into it. -- Mel Gorman SUSE Labs -- 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
