On 07/25/2014 09:27 AM, Wilco Dijkstra wrote: >> On 07/25/2014 08:06 AM, Wilco Dijkstra wrote: >>> Is there a reason Linux does not do background page clearing like other OSes to reduce this >>> overhead? It would be a good fit for typical mobile workloads (bursts of high activity >> followed by >>> periods of low activity). >> >> If the page is being allocated, it is about to be used and be brought in >> to the CPU's cache. If we zero it close to this use, we only pay to >> bring it in to the CPU's cache once. Or so goes the theory... > > I can see the reasoning for 4KB pages and small allocations (eg. stack), > but would that ever be true for huge pages? Probably not, but huge pages aren't allocated and freed enough in any workload that I know of for this to make a difference for them. >> I tried a zero-on-free implementation a year or so ago. It helped some >> workloads and hurt others. The gains were not large enough or >> widespread enough to merit pushing it in to the kernel. > > Was that literally zero-on-free or zero in the background? Was the result > the same for different page sizes? My guess is that the result will be > different for huge pages. Literally zero-on-free for 4k pages only. I did it inside the per-cpu-pages lists. -- 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>