On Thu, 21 Oct 2010 15:49:33 -0500 (CDT) Christoph Lameter <cl@xxxxxxxxx> wrote: > On Thu, 21 Oct 2010, Andrew Morton wrote: > > > On Thu, 21 Oct 2010 15:28:35 -0500 (CDT) > > Christoph Lameter <cl@xxxxxxxxx> wrote: > > > > > On Thu, 21 Oct 2010, Andrew Morton wrote: > > > > > > > The patch changes balance_pgdat() to not shrink slab when inspecting > > > > the highmem zone. It will therefore change zone balancing behaviour on > > > > a humble 1G laptop, will it not? > > > > > > It will avoid a slab shrink call on the HIGHMEM zone that will put useless > > > pressure on the cache objects in ZONE_NORMAL and ZONE_DMA. There will have > > > been already shrinker calls for ZONE_DMA and ZONE_NORMAL before. This is > > > going to be the third round.... > > > > > > > Right, it changes behaviour for modest machines. Apparently accidentally. > > > > Is the new behaviour better, or worse? > > Its bad given that direct reclaim does one call per scan over all zones. > > And it also seems to be useless since all reclaim operates on the same > data right now. So the call for each zone does the same... > > With the per node patch we may be able to get some more finegrained slab > reclaim in the future. But the subsystems are still not distinguishing > caches per zone since slab allocations always occur from ZONE_NORMAL. So > what is the point of the additional calls? > In other words, you don't know! Theoretical design arguments are all well and good. But practical, empirical results rule, and we don't know the practical, empirical effects of this change upon our users. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>