[PATCH v2 0/5] memcg: Support per-memcg KSM metrics

[PATCH v2 0/5] memcg: Support per-memcg KSM metrics

[xu.xin16]

From: xu xin <xu.xin16@zte.com.cn>

Dear all,

This is the v2 of patchset, as Shakeel suggested:
https://lore.kernel.org/all/ir2s6sqi6hrbz7ghmfngbif6fbgmswhqdljlntesurfl2xvmmv@yp3w2lqyipb5/

With the enablement of container-level KSM (e.g., via prctl [1]), there is
a growing demand for container-level observability of KSM behavior. However,
current cgroup implementations lack support for exposing KSM-related metrics.

So add the counter in the existing memory.stat without adding a new interface.
To diaplay per-memcg KSM statistic counters,  we traverse all processes of a
memcg and summing the processes' ksm_rmap_items counters instead of adding enum
item in memcg_stat_item or node_stat_item and updating the corresponding enum
counter when ksmd manipulate pages.

Now Linux users can look up all per-memcg KSM counters by:

# cat /sys/fs/cgroup/xuxin/memory.stat | grep ksm
ksm_rmap_items 0
ksm_zero_pages 0
ksm_merging_pages 0
ksm_profit 0

Q&A
====
why don't I add enum item in memcg_stat_item or node_stat_item like
other items in memory.stat ?

I tried the way of adding enum item in memcg_stat_item and updating them when
ksmd manipulate pages, but it failed with error statistic ksm counters of
memcg. This is because of the following reasons:

1) The KSM counter of memcgroup can be correctly incremented, but cannot be
properly decremented. E,g,, when ksmd scans pages of a process, it can use
the mm_struct of the struct ksm_rmap_item to reverse-lookup the memcg
and then increase the value via mod_memcg_state(memcg, MEMCG_KSM_COUNT, 1).
However, when the process exits abruptly, since ksmd asynchronously scans
the mmslot list in the background, it is no longer able to correctly locate
the original memcg through mm_struct by get_mem_cgroup_from_mm(), as the
task_struct has already been freed.

2) The first issue could potentially be addressed by adding a memcg
pointer directly into the ksm_rmap_item structure. However, this
increases memory overhead, especially when there are a large
number of ksm_rmap_items in the system (due to a high volume of
pages being scanned by ksmd). Moreover, this approach does not
resolve the same problem for ksm_zero_pages, because updates to
ksm_zero_pages are not performed through ksm_rmap_item, but
rather directly during unmap or page table entry (pte) faults
based on the mm_struct. At that point, if the process has
already exited, the corresponding memcg can no longer be
accurately identified.

xu xin (5):
  memcg: add per-memcg ksm_rmap_items stat
  memcg: show ksm_zero_pages count in memory.stat
  memcg: show ksm_merging_pages in memory.stat
  memcg: add per-memcg ksm_profit
  Documentation: add KSM statistic counters description in cgroup-v2.rst

 Documentation/admin-guide/cgroup-v2.rst | 17 +++++++
 include/linux/ksm.h                     |  1 +
 mm/ksm.c                                | 67 ++++++++++++++++++++++---
 mm/memcontrol.c                         |  5 ++
 4 files changed, 84 insertions(+), 6 deletions(-)

-- 
2.25.1

[PATCH v2 1/5] memcg: add per-memcg ksm_rmap_items stat

[xu.xin16]

From: xu xin <xu.xin16@zte.com.cn>

With the enablement of container-level KSM (e.g., via prctl), there is
a growing demand for container-level observability of KSM behavior.

The value of "ksm_rmap_items" indicates the total allocated ksm
rmap_items of this memcg, which could be used to determine how
unbeneficial the ksm-policy (like madvise), they are using brings,
since the bigger the ratio of ksm_rmap_items over ksm_merging_pages,
the more unbeneficial the ksm bring.

Add the counter in the existing memory.stat without adding a new interface.
We traverse all processes of a memcg and summing the processes'
ksm_rmap_items counters instead of adding enum item in memcg_stat_item
or node_stat_item and updating the corresponding enum counter when
ksmd manipulate pages.

Finally, we can look up ksm_rmap_items of per-memcg simply by:

    cat /sys/fs/cgroup/memory.stat | grep ksm_rmap_items

Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 include/linux/ksm.h |  1 +
 mm/ksm.c            | 38 ++++++++++++++++++++++++++++++++++++++
 mm/memcontrol.c     |  5 +++++
 3 files changed, 44 insertions(+)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 22e67ca7cba3..a41ed503f152 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -94,6 +94,7 @@ void collect_procs_ksm(const struct folio *folio, const struct page *page,
 		struct list_head *to_kill, int force_early);
 long ksm_process_profit(struct mm_struct *);
 bool ksm_process_mergeable(struct mm_struct *mm);
+void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s);

 #else  /* !CONFIG_KSM */

diff --git a/mm/ksm.c b/mm/ksm.c
index 2ef29802a49b..b533f0edaf96 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3308,6 +3308,44 @@ long ksm_process_profit(struct mm_struct *mm)
 }
 #endif /* CONFIG_PROC_FS */

+#ifdef CONFIG_MEMCG
+struct memcg_ksm_stat {
+	unsigned long ksm_rmap_items;
+};
+
+static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
+{
+	struct mm_struct *mm;
+	struct memcg_ksm_stat *ksm_stat = arg;
+
+	mm = get_task_mm(task);
+	if (mm) {
+		ksm_stat->ksm_rmap_items += mm->ksm_rmap_items;
+		mmput(mm);
+	}
+
+	return 0;
+}
+
+/* Show the ksm statistic count at memory.stat under cgroup mountpoint */
+void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s)
+{
+	struct memcg_ksm_stat ksm_stat;
+
+	if (mem_cgroup_is_root(memcg)) {
+		/* Just use the global counters when root memcg */
+		ksm_stat.ksm_rmap_items = ksm_rmap_items;
+	} else {
+		/* Initialization */
+		ksm_stat.ksm_rmap_items = 0;
+		/* Summing all processes'ksm statistic items */
+		mem_cgroup_scan_tasks(memcg, evaluate_memcg_ksm_stat, &ksm_stat);
+	}
+	/* Print memcg ksm statistic items */
+	seq_buf_printf(s, "ksm_rmap_items %lu\n", ksm_stat.ksm_rmap_items);
+}
+#endif
+
 #ifdef CONFIG_SYSFS
 /*
  * This all compiles without CONFIG_SYSFS, but is a waste of space.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 257d2c76b730..9595b132c6c3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -63,6 +63,7 @@
 #include <linux/seq_buf.h>
 #include <linux/sched/isolation.h>
 #include <linux/kmemleak.h>
+#include <linux/ksm.h>
 #include "internal.h"
 #include <net/sock.h>
 #include <net/ip.h>
@@ -1492,6 +1493,10 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
 		}
 	}

+#ifdef CONFIG_KSM
+	memcg_stat_ksm_show(memcg, s);
+#endif
+
 	/* Accumulated memory events */
 	seq_buf_printf(s, "pgscan %lu\n",
 		       memcg_events(memcg, PGSCAN_KSWAPD) +
-- 
2.25.1

[PATCH v2 2/5] memcg: show ksm_zero_pages count in memory.stat

[xu.xin16]

From: xu xin <xu.xin16@zte.com.cn>

Users can obtain ksm_zero_pages of a cgroup just by:

    'cat /sys/fs/cgroup/memory.stat | grep ksm_zero_pages

Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 mm/ksm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/ksm.c b/mm/ksm.c
index b533f0edaf96..5832159214f8 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3311,6 +3311,7 @@ long ksm_process_profit(struct mm_struct *mm)
 #ifdef CONFIG_MEMCG
 struct memcg_ksm_stat {
 	unsigned long ksm_rmap_items;
+	long ksm_zero_pages;
 };

 static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
@@ -3321,6 +3322,7 @@ static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
 	mm = get_task_mm(task);
 	if (mm) {
 		ksm_stat->ksm_rmap_items += mm->ksm_rmap_items;
+		ksm_stat->ksm_zero_pages += mm_ksm_zero_pages(mm);
 		mmput(mm);
 	}

@@ -3335,14 +3337,17 @@ void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s)
 	if (mem_cgroup_is_root(memcg)) {
 		/* Just use the global counters when root memcg */
 		ksm_stat.ksm_rmap_items = ksm_rmap_items;
+		ksm_stat.ksm_zero_pages = atomic_long_read(&ksm_zero_pages);
 	} else {
 		/* Initialization */
 		ksm_stat.ksm_rmap_items = 0;
+		ksm_stat.ksm_zero_pages = 0;
 		/* Summing all processes'ksm statistic items */
 		mem_cgroup_scan_tasks(memcg, evaluate_memcg_ksm_stat, &ksm_stat);
 	}
 	/* Print memcg ksm statistic items */
 	seq_buf_printf(s, "ksm_rmap_items %lu\n", ksm_stat.ksm_rmap_items);
+	seq_buf_printf(s, "ksm_zero_pages %lu\n", ksm_stat.ksm_zero_pages);
 }
 #endif

-- 
2.25.1

[PATCH v2 3/5] memcg: show ksm_merging_pages in memory.stat

[xu.xin16]

From: xu xin <xu.xin16@zte.com.cn>

Users can obtain ksm_merging_pages of a cgroup just by:

    'cat /sys/fs/cgroup/memory.stat | grep ksm_merging_pages

Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 mm/ksm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/ksm.c b/mm/ksm.c
index 5832159214f8..4cc47ad1e887 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3312,6 +3312,7 @@ long ksm_process_profit(struct mm_struct *mm)
 struct memcg_ksm_stat {
 	unsigned long ksm_rmap_items;
 	long ksm_zero_pages;
+	unsigned long ksm_merging_pages;
 };

 static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
@@ -3323,6 +3324,7 @@ static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
 	if (mm) {
 		ksm_stat->ksm_rmap_items += mm->ksm_rmap_items;
 		ksm_stat->ksm_zero_pages += mm_ksm_zero_pages(mm);
+		ksm_stat->ksm_merging_pages += mm->ksm_merging_pages;
 		mmput(mm);
 	}

@@ -3338,16 +3340,20 @@ void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s)
 		/* Just use the global counters when root memcg */
 		ksm_stat.ksm_rmap_items = ksm_rmap_items;
 		ksm_stat.ksm_zero_pages = atomic_long_read(&ksm_zero_pages);
+		ksm_stat.ksm_merging_pages = ksm_pages_shared +
+					     ksm_pages_sharing;
 	} else {
 		/* Initialization */
 		ksm_stat.ksm_rmap_items = 0;
 		ksm_stat.ksm_zero_pages = 0;
+		ksm_stat.ksm_merging_pages = 0;
 		/* Summing all processes'ksm statistic items */
 		mem_cgroup_scan_tasks(memcg, evaluate_memcg_ksm_stat, &ksm_stat);
 	}
 	/* Print memcg ksm statistic items */
 	seq_buf_printf(s, "ksm_rmap_items %lu\n", ksm_stat.ksm_rmap_items);
 	seq_buf_printf(s, "ksm_zero_pages %lu\n", ksm_stat.ksm_zero_pages);
+	seq_buf_printf(s, "ksm_merging_pages %lu\n", ksm_stat.ksm_merging_pages);
 }
 #endif

-- 
2.25.1

[PATCH v2 4/5] memcg: add per-memcg ksm_profit

[xu.xin16]

From: xu xin <xu.xin16@zte.com.cn>

Users can obtain ksm_profit of a cgroup just by:

    'cat /sys/fs/cgroup/memory.stat | grep ksm_profit

Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 mm/ksm.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 4cc47ad1e887..c01567a3d5ca 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3308,11 +3308,18 @@ long ksm_process_profit(struct mm_struct *mm)
 }
 #endif /* CONFIG_PROC_FS */

+static inline long ksm_general_profit(void)
+{
+	return (ksm_pages_sharing + atomic_long_read(&ksm_zero_pages)) * PAGE_SIZE -
+		ksm_rmap_items * sizeof(struct ksm_rmap_item);
+}
+
 #ifdef CONFIG_MEMCG
 struct memcg_ksm_stat {
 	unsigned long ksm_rmap_items;
 	long ksm_zero_pages;
 	unsigned long ksm_merging_pages;
+	long ksm_profit;
 };

 static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
@@ -3325,6 +3332,7 @@ static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
 		ksm_stat->ksm_rmap_items += mm->ksm_rmap_items;
 		ksm_stat->ksm_zero_pages += mm_ksm_zero_pages(mm);
 		ksm_stat->ksm_merging_pages += mm->ksm_merging_pages;
+		ksm_stat->ksm_profit += ksm_process_profit(mm);
 		mmput(mm);
 	}

@@ -3342,11 +3350,13 @@ void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s)
 		ksm_stat.ksm_zero_pages = atomic_long_read(&ksm_zero_pages);
 		ksm_stat.ksm_merging_pages = ksm_pages_shared +
 					     ksm_pages_sharing;
+		ksm_stat.ksm_profit = ksm_general_profit();
 	} else {
 		/* Initialization */
 		ksm_stat.ksm_rmap_items = 0;
 		ksm_stat.ksm_zero_pages = 0;
 		ksm_stat.ksm_merging_pages = 0;
+		ksm_stat.ksm_profit = 0;
 		/* Summing all processes'ksm statistic items */
 		mem_cgroup_scan_tasks(memcg, evaluate_memcg_ksm_stat, &ksm_stat);
 	}
@@ -3354,6 +3364,7 @@ void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s)
 	seq_buf_printf(s, "ksm_rmap_items %lu\n", ksm_stat.ksm_rmap_items);
 	seq_buf_printf(s, "ksm_zero_pages %lu\n", ksm_stat.ksm_zero_pages);
 	seq_buf_printf(s, "ksm_merging_pages %lu\n", ksm_stat.ksm_merging_pages);
+	seq_buf_printf(s, "ksm_profit %lu\n", ksm_stat.ksm_profit);
 }
 #endif

@@ -3648,12 +3659,7 @@ KSM_ATTR_RO(ksm_zero_pages);
 static ssize_t general_profit_show(struct kobject *kobj,
 				   struct kobj_attribute *attr, char *buf)
 {
-	long general_profit;
-
-	general_profit = (ksm_pages_sharing + atomic_long_read(&ksm_zero_pages)) * PAGE_SIZE -
-				ksm_rmap_items * sizeof(struct ksm_rmap_item);
-
-	return sysfs_emit(buf, "%ld\n", general_profit);
+	return sysfs_emit(buf, "%ld\n", ksm_general_profit());
 }
 KSM_ATTR_RO(general_profit);

-- 
2.25.1

[PATCH v2 5/5] Documentation: add KSM statistic counters description in cgroup-v2.rst

[xu.xin16]

From: xu xin <xu.xin16@zte.com.cn>

This add KSM-related statistic counters description in cgroup-v2.rst,
including "ksm_rmap_items", "ksm_zero_pages", "ksm_merging_pages" and
"ksm_profit".

Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 Documentation/admin-guide/cgroup-v2.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index a1e3d431974c..c8c4faa4e3fd 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1776,6 +1776,23 @@ The following nested keys are defined.
 		up if hugetlb usage is accounted for in memory.current (i.e.
 		cgroup is mounted with the memory_hugetlb_accounting option).

+	  ksm_rmap_items
+		Number of ksm_rmap_item structures in use. The structure
+		ksm_rmap_item stores the reverse mapping information for virtual
+		addresses.  KSM will generate a ksm_rmap_item for each
+		ksm-scanned page of the process.
+
+	  ksm_zero_pages
+		Number of empty pages are merged with kernel zero pages by KSM,
+		which is only useful when /sys/kernel/mm/ksm/use_zero_pages.
+
+	  ksm_merging_pages
+		Number of pages of this process are involved in KSM merging
+		(not including ksm_zero_pages).
+
+	  ksm_profit
+		Amount of profitable memory that KSM brings (Saved bytes).
+
   memory.numa_stat
 	A read-only nested-keyed file which exists on non-root cgroups.

-- 
2.25.1

Re: [PATCH v2 4/5] memcg: add per-memcg ksm_profit

[kernel test robot]

Hi,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on tj-cgroup/for-next linus/master v6.17-rc5 next-20250912]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/xu-xin16-zte-com-cn/memcg-add-per-memcg-ksm_rmap_items-stat/20250914-181132
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250914180750448qMRz3iTon78DoExPyZusD%40zte.com.cn
patch subject: [PATCH v2 4/5] memcg: add per-memcg ksm_profit
config: um-randconfig-001-20250914 (https://download.01.org/0day-ci/archive/20250914/202509142046.QatEaTQV-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 21857ae337e0892a5522b6e7337899caa61de2a6)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250914/202509142046.QatEaTQV-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509142046.QatEaTQV-lkp@intel.com/

All errors (new ones prefixed by >>):

   /usr/bin/ld: warning: .tmp_vmlinux1 has a LOAD segment with RWX permissions
   /usr/bin/ld: mm/ksm.o: in function `evaluate_memcg_ksm_stat':
>> mm/ksm.c:3335:(.ltext+0x163d): undefined reference to `ksm_process_profit'
   clang: error: linker command failed with exit code 1 (use -v to see invocation)


vim +3335 mm/ksm.c

  3324	
  3325	static int evaluate_memcg_ksm_stat(struct task_struct *task, void *arg)
  3326	{
  3327		struct mm_struct *mm;
  3328		struct memcg_ksm_stat *ksm_stat = arg;
  3329	
  3330		mm = get_task_mm(task);
  3331		if (mm) {
  3332			ksm_stat->ksm_rmap_items += mm->ksm_rmap_items;
  3333			ksm_stat->ksm_zero_pages += mm_ksm_zero_pages(mm);
  3334			ksm_stat->ksm_merging_pages += mm->ksm_merging_pages;
> 3335			ksm_stat->ksm_profit += ksm_process_profit(mm);
  3336			mmput(mm);
  3337		}
  3338	
  3339		return 0;
  3340	}
  3341	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 1/5] memcg: add per-memcg ksm_rmap_items stat

[kernel test robot]

Hi,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]
[also build test ERROR on tj-cgroup/for-next linus/master v6.17-rc5 next-20250912]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/xu-xin16-zte-com-cn/memcg-add-per-memcg-ksm_rmap_items-stat/20250914-181132
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250914180351288rcLuZnPAMUej48nuTc7KV%40zte.com.cn
patch subject: [PATCH v2 1/5] memcg: add per-memcg ksm_rmap_items stat
config: parisc-randconfig-001-20250914 (https://download.01.org/0day-ci/archive/20250914/202509142147.WQI0impC-lkp@intel.com/config)
compiler: hppa-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250914/202509142147.WQI0impC-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509142147.WQI0impC-lkp@intel.com/

All errors (new ones prefixed by >>):

   mm/ksm.c: In function 'memcg_stat_ksm_show':
>> mm/ksm.c:3345:2: error: implicit declaration of function 'seq_buf_printf'; did you mean 'seq_bprintf'? [-Werror=implicit-function-declaration]
     seq_buf_printf(s, "ksm_rmap_items %lu\n", ksm_stat.ksm_rmap_items);
     ^~~~~~~~~~~~~~
     seq_bprintf
   cc1: some warnings being treated as errors


vim +3345 mm/ksm.c

  3329	
  3330	/* Show the ksm statistic count at memory.stat under cgroup mountpoint */
  3331	void memcg_stat_ksm_show(struct mem_cgroup *memcg, struct seq_buf *s)
  3332	{
  3333		struct memcg_ksm_stat ksm_stat;
  3334	
  3335		if (mem_cgroup_is_root(memcg)) {
  3336			/* Just use the global counters when root memcg */
  3337			ksm_stat.ksm_rmap_items = ksm_rmap_items;
  3338		} else {
  3339			/* Initialization */
  3340			ksm_stat.ksm_rmap_items = 0;
  3341			/* Summing all processes'ksm statistic items */
  3342			mem_cgroup_scan_tasks(memcg, evaluate_memcg_ksm_stat, &ksm_stat);
  3343		}
  3344		/* Print memcg ksm statistic items */
> 3345		seq_buf_printf(s, "ksm_rmap_items %lu\n", ksm_stat.ksm_rmap_items);
  3346	}
  3347	#endif
  3348	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki