diff options
| -rw-r--r-- | include/linux/page-flags.h | 28 | ||||
| -rw-r--r-- | mm/Kconfig | 12 |
2 files changed, 40 insertions, 0 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index d16efa9066d9..590cff32415d 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -83,7 +83,12 @@ enum pageflags { PG_reserved, PG_private, /* If pagecache, has fs-private data */ PG_writeback, /* Page is under writeback */ +#ifdef CONFIG_PAGEFLAGS_EXTENDED + PG_head, /* A head page */ + PG_tail, /* A tail page */ +#else PG_compound, /* A compound page */ +#endif PG_swapcache, /* Swap page: swp_entry_t in private */ PG_mappedtodisk, /* Has blocks allocated on-disk */ PG_reclaim, /* To be reclaimed asap */ @@ -248,6 +253,28 @@ static inline void set_page_writeback(struct page *page) test_set_page_writeback(page); } +#ifdef CONFIG_PAGEFLAGS_EXTENDED +/* + * System with lots of page flags available. This allows separate + * flags for PageHead() and PageTail() checks of compound pages so that bit + * tests can be used in performance sensitive paths. PageCompound is + * generally not used in hot code paths. + */ +__PAGEFLAG(Head, head) +__PAGEFLAG(Tail, tail) + +static inline int PageCompound(struct page *page) +{ + return page->flags & ((1L << PG_head) | (1L << PG_tail)); + +} +#else +/* + * Reduce page flag use as much as possible by overlapping + * compound page flags with the flags used for page cache pages. Possible + * because PageCompound is always set for compound pages and not for + * pages on the LRU and/or pagecache. + */ TESTPAGEFLAG(Compound, compound) __PAGEFLAG(Head, compound) @@ -278,5 +305,6 @@ static inline void __ClearPageTail(struct page *page) page->flags &= ~PG_head_tail_mask; } +#endif /* !PAGEFLAGS_EXTENDED */ #endif /* !__GENERATING_BOUNDS_H */ #endif /* PAGE_FLAGS_H */ diff --git a/mm/Kconfig b/mm/Kconfig index 0016ebd4dcba..3aa819d628c1 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -143,6 +143,18 @@ config MEMORY_HOTREMOVE depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE depends on MIGRATION +# +# If we have space for more page flags then we can enable additional +# optimizations and functionality. +# +# Regular Sparsemem takes page flag bits for the sectionid if it does not +# use a virtual memmap. Disable extended page flags for 32 bit platforms +# that require the use of a sectionid in the page flags. +# +config PAGEFLAGS_EXTENDED + def_bool y + depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !SPARSEMEM + # Heavily threaded applications may benefit from splitting the mm-wide # page_table_lock, so that faults on different parts of the user address # space can be handled with less contention: split it at this NR_CPUS. |