From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> Date: Thu, 04 Oct 2012 22:00:48 +0530 > David Miller <davem@xxxxxxxxxxxxx> writes: > >> We've split up the PTE tables so that they take up half a page instead >> of a full page. This is in order to facilitate transparent huge page >> support, which works much better if our PMDs cover 4MB instead of 8MB. >> >> What we do is have a one-behind cache for PTE table allocations in the >> mm struct. >> >> This logic triggers only on allocations. For example, we don't try to >> keep track of free'd up page table blocks in the style that the s390 >> port does. > > I am also implementing a similar change for powerpc. We have a 64K page > size, and want to make sure PMD cover 16MB, which is the huge page size > supported by the hardware. I was looking at using the s390 logic, > considering we have 16 PMDs mapping to same PTE page. Should we look at > generalizing the case so that other architectures can start using the > same code ? I think until we have multiple cases we won't know what's common or not. Each arch has different need. I need to split the page into two pieces so my code is simpler, and juse uses page counting to manage alloc/free. Whereas s390 uses an bitmask to manage page state, and also reclaims pgtable pages into a per-mm list on free. I decided not to do that and to just let the page allocator do the work. So I don't think it's appropriate to think about commonization at this time, as even the only two cases existing are very non-common :-) -- 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>