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Patch series "Rearrange struct page", v6. As presented at LSFMM, this patch-set rearranges struct page to give more contiguous usable space to users who have allocated a struct page for their own purposes. For a graphical view of before-and-after, see the first two tabs of https://docs.google.com/spreadsheets/d/1tvCszs_7FXrjei9_mtFiKV6nW1FLnYyvPvW-qNZhdog/edit?usp=sharing Highlights: - deferred_list now really exists in struct page instead of just a comment. - hmm_data also exists in struct page instead of being a nasty hack. - x86's PGD pages have a real pointer to the mm_struct. - VMalloc pages now have all sorts of extra information stored in them to help with debugging and tuning. - rcu_head is no longer tied to slab in case anyone else wants to free pages by RCU. - slub's counters no longer share space with _refcount. - slub's freelist+counters are now naturally dword aligned. - slub loses a parameter to a lot of functions and a sysfs file. This patch (of 17): s390 borrows the storage used for _mapcount in struct page in order to account whether the bottom or top half is being used for 2kB page tables. I want to use that for something else, so use the top byte of _refcount instead of the bottom byte of _mapcount. _refcount may temporarily be incremented by other CPUs that see a stale pointer to this page in the page cache, but each CPU can only increment it by one, and there are no systems with 2^24 CPUs today, so they will not change the upper byte of _refcount. We do have to be a little careful not to lose any of their writes (as they will subsequently decrement the counter). Link: http://lkml.kernel.org/r/20180518194519.3820-2-willy@infradead.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Christoph Lameter <cl@linux.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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