diff options
| -rw-r--r-- | include/linux/page-flags.h | 11 | ||||
| -rw-r--r-- | mm/Kconfig | 10 | ||||
| -rw-r--r-- | mm/ksm.c | 33 |
3 files changed, 52 insertions, 2 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 40edce1..b38dc8d 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -114,8 +114,15 @@ enum pageflags { PG_was_active, #endif PG_readahead, /* page in a readahead window */ +#ifdef CONFIG_KSM_CHECK_PAGE + PG_ksm_scan0, /* page has been scanned by even KSM cycle */ +#endif __NR_PAGEFLAGS, +#ifdef CONFIG_KSM_CHECK_PAGE + /* page has been scanned by odd KSM cycle */ + PG_ksm_scan1 = PG_owner_priv_1, +#endif /* Filesystems */ PG_checked = PG_owner_priv_1, @@ -218,6 +225,10 @@ PAGEFLAG(Reserved, reserved) __CLEARPAGEFLAG(Reserved, reserved) PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked) __PAGEFLAG(SlobFree, slob_free) +#ifdef CONFIG_KSM_CHECK_PAGE +CLEARPAGEFLAG(KsmScan0, ksm_scan0) TESTSETFLAG(KsmScan0, ksm_scan0) +CLEARPAGEFLAG(KsmScan1, ksm_scan1) TESTSETFLAG(KsmScan1, ksm_scan1) +#endif __PAGEFLAG(SlubFrozen, slub_frozen) @@ -237,6 +237,16 @@ config KSM until a program has madvised that an area is MADV_MERGEABLE, and root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). +config KSM_CHECK_PAGE + bool "Check page before scanning" + depends on KSM + default n + help + If enabled, this will check and skip if page is already scanned in + same KSM scan cycle. + This is useful in situation where you have parent and + child process marking same area for KSM scanning. + config DEFAULT_MMAP_MIN_ADDR int "Low address space to protect from user allocation" depends on MMU @@ -554,7 +554,9 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) * than left over from before. */ age = (unsigned char)(ksm_scan.seqnr - rmap_item->address); +#ifndef CONFIG_KSM_CHECK_PAGE BUG_ON(age > 1); +#endif if (!age) rb_erase(&rmap_item->node, &root_unstable_tree); @@ -1403,6 +1405,31 @@ next_mm: return NULL; } +static inline int is_page_scanned(struct page *page) +{ +#ifdef CONFIG_KSM_CHECK_PAGE + /* page is already marked as ksm, so this will be simple merge */ + if (PageKsm(page)) + return 0; + + if (ksm_scan.seqnr & 0x1) { + /* odd cycle */ + /* clear even cycle bit */ + ClearPageKsmScan0(page); + /* get old value and mark it scanned */ + return TestSetPageKsmScan1(page); + } else { + /* even cycle */ + /* clear odd cycle bit */ + ClearPageKsmScan1(page); + /* get old value and mark it scanned */ + return TestSetPageKsmScan0(page); + } +#else + return 0; +#endif +} + /** * ksm_do_scan - the ksm scanner main worker function. * @scan_npages - number of pages we want to scan before we return. @@ -1417,8 +1444,10 @@ static void ksm_do_scan(unsigned int scan_npages) rmap_item = scan_get_next_rmap_item(&page); if (!rmap_item) return; - if (!PageKsm(page) || !in_stable_tree(rmap_item)) - cmp_and_merge_page(page, rmap_item); + if (!PageKsm(page) || !in_stable_tree(rmap_item)) { + if (!is_page_scanned(page)) + cmp_and_merge_page(page, rmap_item); + } put_page(page); } } |