mainline inclusion
from mainline-v5.19-rc1
commit 76093853
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I72R0B
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7609385337a4feb6236e42dcd0df2185683ce839

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Some applications or containers want to use KSM by calling madvise() to
advise areas of address space to be MERGEABLE.  But they may not know
which applications are more likely to cause real merges in the
deployment.  If this patch is applied, it helps them know their
corresponding number of merged pages, and then optimize their app code.

As current KSM only counts the number of KSM merging pages(e.g.
ksm_pages_sharing and ksm_pages_shared) of the whole system, we cannot see
the more fine-grained KSM merging, for the upper application optimization,
the merging area cannot be set easily according to the KSM page merging
probability of each process.  Therefore, it is necessary to add extra
statistical means so that the upper level users can know the detailed KSM
merging information of each process.

We add a new proc file named as ksm_merging_pages under /proc/<pid>/ to
indicate the involved ksm merging pages of this process.

[akpm@linux-foundation.org: fix comment typo, remove BUG_ON()s]
Link: https://lkml.kernel.org/r/20220325082318.2352853-1-xu.xin16@zte.com.cnSigned-off-by: Nxu xin <xu.xin16@zte.com.cn>
Reported-by: Nkernel test robot <lkp@intel.com>
Reviewed-by: NYang Yang <yang.yang29@zte.com.cn>
Reviewed-by: NRan Xiaokai <ran.xiaokai@zte.com.cn>
Reported-by: NZeal Robot <zealci@zte.com.cn>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Ohhoon Kwon <ohoono.kwon@samsung.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Conflicts:
	include/linux/mm_types.h
Signed-off-by: NNanyong Sun <sunnanyong@huawei.com>