From: xu xin <cgel.zte@gmail.com> mainline inclusion from mainline-v6.1-rc1 commit cb4df4cae4f2bd8cf7a32eff81178fce31600f7c category: feature bugzilla: https://atomgit.com/openeuler/kernel/issues/10169 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Patch series "ksm: count allocated rmap_items and update documentation", v5. KSM can save memory by merging identical pages, but also can consume additional memory, because it needs to generate rmap_items to save each scanned page's brief rmap information. To determine how beneficial the ksm-policy (like madvise), they are using brings, so we add a new interface /proc/<pid>/ksm_stat for each process The value "ksm_rmap_items" in it indicates the total allocated ksm rmap_items of this process. The detailed description can be seen in the following patches' commit message. This patch (of 2): KSM can save memory by merging identical pages, but also can consume additional memory, because it needs to generate rmap_items to save each scanned page's brief rmap information. Some of these pages may be merged, but some may not be abled to be merged after being checked several times, which are unprofitable memory consumed. The information about whether KSM save memory or consume memory in system-wide range can be determined by the comprehensive calculation of pages_sharing, pages_shared, pages_unshared and pages_volatile. A simple approximate calculation: profit =~ pages_sharing * sizeof(page) - (all_rmap_items) * sizeof(rmap_item); where all_rmap_items equals to the sum of pages_sharing, pages_shared, pages_unshared and pages_volatile. But we cannot calculate this kind of ksm profit inner single-process wide because the information of ksm rmap_item's number of a process is lacked. For user applications, if this kind of information could be obtained, it helps upper users know how beneficial the ksm-policy (like madvise) they are using brings, and then optimize their app code. For example, one application madvise 1000 pages as MERGEABLE, while only a few pages are really merged, then it's not cost-efficient. So we add a new interface /proc/<pid>/ksm_stat for each process in which the value of ksm_rmap_itmes is only shown now and so more values can be added in future. So similarly, we can calculate the ksm profit approximately for a single process by: profit =~ ksm_merging_pages * sizeof(page) - ksm_rmap_items * sizeof(rmap_item); where ksm_merging_pages is shown at /proc/<pid>/ksm_merging_pages, and ksm_rmap_items is shown in /proc/<pid>/ksm_stat. Link: https://lkml.kernel.org/r/20220830143731.299702-1-xu.xin16@zte.com.cn Link: https://lkml.kernel.org/r/20220830143838.299758-1-xu.xin16@zte.com.cn Signed-off-by: xu xin <xu.xin16@zte.com.cn> Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn> Signed-off-by: CGEL ZTE <cgel.zte@gmail.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Bagas Sanjaya <bagasdotme@gmail.com> Cc: Hugh Dickins <hughd@google.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: fs/proc/base.c include/linux/mm_types.h [Context conflicts.] Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- fs/proc/base.c | 15 +++++++++++++++ include/linux/mm_types.h | 9 +++++++++ mm/ksm.c | 2 ++ 3 files changed, 26 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index 1807474532d1..6b1622c2085e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3056,6 +3056,19 @@ static int proc_pid_ksm_merging_pages(struct seq_file *m, struct pid_namespace * return 0; } +static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *task) +{ + struct mm_struct *mm; + + mm = get_task_mm(task); + if (mm) { + seq_printf(m, "ksm_rmap_items %lu\n", mm->ksm_rmap_items); + mmput(mm); + } + + return 0; +} #endif /* CONFIG_KSM */ /* @@ -3169,6 +3182,7 @@ static const struct pid_entry tgid_base_stuff[] = { #endif #ifdef CONFIG_KSM ONE("ksm_merging_pages", S_IRUSR, proc_pid_ksm_merging_pages), + ONE("ksm_stat", S_IRUSR, proc_pid_ksm_stat), #endif }; @@ -3558,6 +3572,7 @@ static const struct pid_entry tid_base_stuff[] = { #endif #ifdef CONFIG_KSM ONE("ksm_merging_pages", S_IRUSR, proc_pid_ksm_merging_pages), + ONE("ksm_stat", S_IRUSR, proc_pid_ksm_stat), #endif }; diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5bba4140936c..2db486c0ee5b 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -573,7 +573,16 @@ struct mm_struct { #else KABI_RESERVE(4) #endif + +#if defined(CONFIG_KSM) && !defined(__GENKSYMS__) + /* + * Represent how many pages are checked for ksm merging + * including merged and not merged. + */ + unsigned long ksm_rmap_items; +#else KABI_RESERVE(5) +#endif KABI_RESERVE(6) KABI_RESERVE(7) KABI_RESERVE(8) diff --git a/mm/ksm.c b/mm/ksm.c index f45d0178bd05..82eafea0c1b7 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -389,6 +389,7 @@ static inline struct rmap_item *alloc_rmap_item(void) static inline void free_rmap_item(struct rmap_item *rmap_item) { ksm_rmap_items--; + rmap_item->mm->ksm_rmap_items--; rmap_item->mm = NULL; /* debug safety */ kmem_cache_free(rmap_item_cache, rmap_item); } @@ -2244,6 +2245,7 @@ static struct rmap_item *get_next_rmap_item(struct mm_slot *mm_slot, if (rmap_item) { /* It has already been zeroed */ rmap_item->mm = mm_slot->mm; + rmap_item->mm->ksm_rmap_items++; rmap_item->address = addr; rmap_item->rmap_list = *rmap_list; *rmap_list = rmap_item; -- 2.43.0