On Wed, Jan 29, 2014 at 09:52:46PM -0700, Matthew Wilcox wrote: > On Fri, Jan 24, 2014 at 10:57:48AM +0000, Mel Gorman wrote: > > So far on the table is > > > > 1. major filesystem overhawl > > 2. major vm overhawl > > 3. use compound pages as they are today and hope it does not go > > completely to hell, reboot when it does > > Is the below paragraph an exposition of option 2, or is it an option 4, > change the VM unit of allocation? Other than the names you're using, > this is basically what I said to Kirill in an earlier thread; either > scrap the difference between PAGE_SIZE and PAGE_CACHE_SIZE, or start > making use of it. Christoph Lamater's compound page patch set scrapped PAGE_CACHE_SIZE and made it a variable that was set on the struct address_space when it was instantiated by the filesystem. In effect, it allowed filesystems to specify the unit of page cache allocation on a per-inode basis. > The fact that EVERYBODY in this thread has been using PAGE_SIZE when they > should have been using PAGE_CACHE_SIZE makes me wonder if part of the > problem is that the split in naming went the wrong way. ie use PTE_SIZE > for 'the amount of memory pointed to by a pte_t' and use PAGE_SIZE for > 'the amount of memory described by a struct page'. PAGE_CACHE_SIZE was never distributed sufficiently to be used, and if you #define it to something other than PAGE_SIZE stuff will simply break. > (we need to remove the current users of PTE_SIZE; sparc32 and powerpc32, > but that's just a detail) > > And we need to fix all the places that are currently getting the > distinction wrong. SMOP ... ;-) What would help is correct typing of > variables, possibly with sparse support to help us out. Big Job. Yes, that's what the Christoph's patchset did. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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>