On Fri, Jul 12, 2013 at 10:27:56AM +0200, Ingo Molnar wrote: > > * Robin Holt <holt@xxxxxxx> wrote: > > > [...] > > > > With this patch, we did boot a 16TiB machine. Without the patches, the > > v3.10 kernel with the same configuration took 407 seconds for > > free_all_bootmem. With the patches and operating on 2MiB pages instead > > of 1GiB, it took 26 seconds so performance was improved. I have no feel > > for how the 1GiB chunk size will perform. > > That's pretty impressive. And WRONG! That is a 15x speedup in the freeing of memory at the free_all_bootmem point. That is _NOT_ the speedup from memmap_init_zone. I forgot to take that into account as Nate pointed out this morning in a hallway discussion. Before, on the 16TiB machine, memmap_init_zone took 1152 seconds. After, it took 50. If it were a straight 1/512th, we would have expected that 1152 to be something more on the line of 2-3 so there is still significant room for improvement. Sorry for the confusion. > It's still a 15x speedup instead of a 512x speedup, so I'd say there's > something else being the current bottleneck, besides page init > granularity. > > Can you boot with just a few gigs of RAM and stuff the rest into hotplug > memory, and then hot-add that memory? That would allow easy profiling of > remaining overhead. Nate and I will be working on other things for the next few hours hoping there is a better answer to the first question we asked about there being a way to test a page other than comparing against all zeroes to see if it has been initialized. Thanks, Robin -- 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>