On Thu, 16 Apr 2015 09:46:09 +0100 Mel Gorman <mgorman@xxxxxxx> wrote: > On Thu, Apr 16, 2015 at 12:25:01AM -0700, Andrew Morton wrote: > > On Mon, 13 Apr 2015 11:16:52 +0100 Mel Gorman <mgorman@xxxxxxx> wrote: > > > > > Memory initialisation > > > > I wish we didn't call this "memory initialization". Because memory > > initialization is memset(), and that isn't what we're doing here. > > > > Installation? Bringup? > > > > It's about linking the struct pages to their physical page frame so > "Parallel struct page initialisation"? Works for me. > > I'd hoped the way we were > > going to do this was by bringing up a bit of memory to get booted up, > > then later on we just fake a bunch of memory hot-add operations. So > > the new code would be pretty small and quite high-level. > > That ends up being very complex but of a very different shape. We would > still have to prevent the sections being initialised similar to what this > series does already except the zone boundaries are lower. It's not as > simple as faking mem= because we want local memory on each node during > initialisation. Why do "we want..."? > Later after device_init when sysfs is setup we would then have to walk all > possible sections to discover pluggable memory and hot-add them. However, > when doing it, we would want to first discover what node that section is > local to and ideally skip over the ones that are not local to the thread > doing the work. This means all threads have to scan all sections instead > of this approach which can walk within its own PFN. It then adds pages > one at a time which is slow although obviously that part could be addressed. > > This would be harder to co-ordinate as kswapd is up and running before > the memory hot-add structures are finalised so it would need either a > semaphore or different threads to do the initialisation. The user-visible > impact is then that early in boot, the total amount of memory appears to > be rapidly increasing instead of this approach where the amount of free > memory is increasing. > > Conceptually it's straight forward but the details end up being a lot > more complex than this approach. Could we do most of the think work in userspace, emit a bunch of low-level hotplug operations to the kernel? -- 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>