On Wed, 14 Jul 2010 16:35:22 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > On Wed, Jul 14, 2010 at 4:10 PM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > On Wed, 14 Jul 2010 15:44:41 +0900 > > Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > > > >> Hi, Kame. > >> > >> On Wed, Jul 14, 2010 at 9:23 AM, KAMEZAWA Hiroyuki > >> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > >> > On Wed, 14 Jul 2010 01:44:23 +0900 > >> > Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > >> > > >> >> > If you _really_ can't make the section size smaller, and the vast > >> >> > majority of the sections are fully populated, you could hack something > >> >> > in. We could, for instance, have a global list that's mostly readonly > >> >> > which tells you which sections need to be have their sizes closely > >> >> > inspected. That would work OK if, for instance, you only needed to > >> >> > check a couple of memory sections in the system. It'll start to suck if > >> >> > you made the lists very long. > >> >> > >> >> Thanks for advise. As I say, I hope Russell accept 16M section. > >> >> > >> > > >> > It seems what I needed was good sleep.... > >> > How about this if 16M section is not acceptable ? > >> > > >> > == NOT TESTED AT ALL, EVEN NOT COMPILED == > >> > > >> > register address of mem_section to memmap itself's page struct's pg->private field. > >> > This means the page is used for memmap of the section. > >> > Otherwise, the page is used for other purpose and memmap has a hole. > >> > >> It's a very good idea. :) > >> But can this handle case that a page on memmap pages have struct page > >> descriptor of hole? > >> I mean one page can include 128 page descriptor(4096 / 32). > > yes. > > > >> In there, 64 page descriptor is valid but remain 64 page descriptor is on hole. > >> In this case, free_memmap doesn't free the page. > > > > yes. but in that case, there are valid page decriptor for 64pages of holes. > > pfn_valid() should return true but PG_reserved is set. > > (This is usual behavior.) > > > > My intention is that > > > > - When all 128 page descriptors are unused, free_memmap() will free it. > > In that case, clear page->private of a page for freed page descriptors. > > > > - When some of page descriptors are used, free_memmap() can't free it > > and page->private points to &mem_section. We may have memmap for memory > > hole but pfn_valid() is a function to check there is memmap or not. > > The bahavior of pfn_valid() is valid. > > Anyway, you can't free only half of page. > > Okay. I missed PageReserved. > Your idea seems to be good. :) > > I looked at pagetypeinfo_showblockcount_print. > It doesn't check PageReserved. Instead of it, it does ugly memmap_valid_within. > Can't we remove it and change it with PageReserved? > maybe. but I'm not sure how many archs uses CONFIG_ARCH_HAS_HOLES_MEMORYMODEL. Because my idea requires to add arch-dependent hook, enhancement of pfn_valid() happens only when an arch supports it. So, you may need a conservative path. Anyway, I can't test the patch by myself. So, I pass ball to ARM guys. Feel free to reuse my idea if you like. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Thanks, -Kame -- 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>