On Fri, 14 Jun 2013, Roman Gushchin wrote: > Slub tries to allocate contiguous pages even if memory is fragmented and > there are no free contiguous pages. In this case it calls direct compaction > to allocate contiguous page. Compaction requires the taking of some heavily > contended locks (e.g. zone locks). So, running compaction (direct and using > kswapd) simultaneously on several processors can cause serious performance > issues. The main thing that this patch does is to add a nocompact flag to the page allocator. That needs to be a separate patch. Also fix the description. Slub does not invoke compaction. The page allocator initiates compaction under certain conditions. > It's possible to avoid such problems (or at least to make them less probable) > by avoiding direct compaction. If it's not possible to allocate a contiguous > page without compaction, slub will fall back to order 0 page(s). In this case > kswapd will be woken to perform asynchronous compaction. So, slub can return > to default order allocations as soon as memory will be de-fragmented. Sounds like a good idea. Do you have some numbers to show the effect of this patch? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>