[PATCH v5] mm: cma: support sysfs

Minchan Kim
2021-03-23T19:50:58Z

Since CMA is getting used more widely, it's more important to
keep monitoring CMA statistics for system health since it's
directly related to user experience.

This patch introduces sysfs statistics for CMA, in order to provide
some basic monitoring of the CMA allocator.

* the number of CMA page successful allocations
* the number of CMA page allocation failures

These two values allow the user to calcuate the allocation
failure rate for each CMA area.

e.g.)
/sys/kernel/mm/cma/WIFI/alloc_pages_[success|fail]
/sys/kernel/mm/cma/SENSOR/alloc_pages_[success|fail]
/sys/kernel/mm/cma/BLUETOOTH/alloc_pages_[success|fail]

The cma_stat was intentionally allocated by dynamic allocation
to harmonize with kobject lifetime management.
https://lore.kernel.org/linux-mm/YCOAmXqt6dZkCQYs@kroah.com/

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
From v4 - https://lore.kernel.org/linux-mm/20210309062333.3216138-1-minchan@kernel.org/
* fix corruption - digetx@

From v3 - https://lore.kernel.org/linux-mm/20210303205053.2906924-1-minchan@kernel.org/
* fix ZERO_OR_NULL_PTR - kernel test robot
* remove prefix cma - david@
* resolve conflict with vmstat cma in mmotm - akpm@
* rename stat name with success|fail

From v2 - https://lore.kernel.org/linux-mm/20210208180142.2765456-1-minchan@kernel.org/
* sysfs doc and description modification - jhubbard

From v1 - https://lore.kernel.org/linux-mm/20210203155001.4121868-1-minchan@kernel.org/
* fix sysfs build and refactoring - willy
* rename and drop some attributes - jhubbard

Documentation/ABI/testing/sysfs-kernel-mm-cma | 25 ++++
mm/Kconfig | 7 ++
mm/Makefile | 1 +
mm/cma.c | 7 +-
mm/cma.h | 21 ++++
mm/cma_sysfs.c | 107 ++++++++++++++++++
6 files changed, 166 insertions(+), 2 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-cma
create mode 100644 mm/cma_sysfs.c

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-cma b/Documentation/ABI/testing/sysfs-kernel-mm-cma
new file mode 100644
index 000000000000..02b2bb60c296
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-cma
@@ -0,0 +1,25 @@
+What: /sys/kernel/mm/cma/
+Date: Feb 2021
+Contact: Minchan Kim <minchan@kernel.org>
+Description:
+ /sys/kernel/mm/cma/ contains a subdirectory for each CMA
+ heap name (also sometimes called CMA areas).
+
+ Each CMA heap subdirectory (that is, each
+ /sys/kernel/mm/cma/<cma-heap-name> directory) contains the
+ following items:
+
+ alloc_pages_success
+ alloc_pages_fail
+
+What: /sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_success
+Date: Feb 2021
+Contact: Minchan Kim <minchan@kernel.org>
+Description:
+ the number of pages CMA API succeeded to allocate
+
+What: /sys/kernel/mm/cma/<cma-heap-name>/alloc_pages_fail
+Date: Feb 2021
+Contact: Minchan Kim <minchan@kernel.org>
+Description:
+ the number of pages CMA API failed to allocate
diff --git a/mm/Kconfig b/mm/Kconfig
index 24c045b24b95..febb7e8e24de 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -513,6 +513,13 @@ config CMA_DEBUGFS
help
Turns on the DebugFS interface for CMA.

+config CMA_SYSFS
+ bool "CMA information through sysfs interface"
+ depends on CMA && SYSFS
+ help
+ This option exposes some sysfs attributes to get information
+ from CMA.
+
config CMA_AREAS
int "Maximum count of the CMA areas"
depends on CMA
diff --git a/mm/Makefile b/mm/Makefile
index 72227b24a616..56968b23ed7a 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -109,6 +109,7 @@ obj-$(CONFIG_CMA) += cma.o
obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o
obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o
obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o
+obj-$(CONFIG_CMA_SYSFS) += cma_sysfs.o
obj-$(CONFIG_USERFAULTFD) += userfaultfd.o
obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o
obj-$(CONFIG_DEBUG_PAGE_REF) += debug_page_ref.o
diff --git a/mm/cma.c b/mm/cma.c
index 908f04775686..ac050359faae 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -507,10 +507,13 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,

pr_debug("%s(): returned %p\n", __func__, page);
out:
- if (page)
+ if (page) {
count_vm_event(CMA_ALLOC_SUCCESS);
- else
+ cma_sysfs_alloc_pages_count(cma, count);
+ } else {
count_vm_event(CMA_ALLOC_FAIL);
+ cma_sysfs_fail_pages_count(cma, count);
+ }

return page;
}
diff --git a/mm/cma.h b/mm/cma.h
index 42ae082cb067..f3258791ac58 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -3,6 +3,12 @@
#define __MM_CMA_H__

#include <linux/debugfs.h>
+#include <linux/kobject.h>
+
+struct cma_kobject {
+ struct cma *cma;
+ struct kobject kobj;
+};

struct cma {
unsigned long base_pfn;
@@ -16,6 +22,14 @@ struct cma {
struct debugfs_u32_array dfs_bitmap;
#endif
char name[CMA_MAX_NAME];
+#ifdef CONFIG_CMA_SYSFS
+ /* the number of CMA page successful allocations */
+ atomic64_t nr_pages_succeeded;
+ /* the number of CMA page allocation failures */
+ atomic64_t nr_pages_failed;
+ /* kobject requires dynamic objecjt */
+ struct cma_kobject *kobj;
+#endif
};

extern struct cma cma_areas[MAX_CMA_AREAS];
@@ -26,4 +40,11 @@ static inline unsigned long cma_bitmap_maxno(struct cma *cma)
return cma->count >> cma->order_per_bit;
}

+#ifdef CONFIG_CMA_SYSFS
+void cma_sysfs_alloc_pages_count(struct cma *cma, size_t count);
+void cma_sysfs_fail_pages_count(struct cma *cma, size_t count);
+#else
+static inline void cma_sysfs_alloc_pages_count(struct cma *cma, size_t count) {};
+static inline void cma_sysfs_fail_pages_count(struct cma *cma, size_t count) {};
+#endif
#endif
diff --git a/mm/cma_sysfs.c b/mm/cma_sysfs.c
new file mode 100644
index 000000000000..6813635cef41
--- /dev/null
+++ b/mm/cma_sysfs.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * CMA SysFS Interface
+ *
+ * Copyright (c) 2021 Minchan Kim <minchan@kernel.org>
+ */
+
+#include <linux/cma.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "cma.h"
+
+void cma_sysfs_alloc_pages_count(struct cma *cma, size_t count)
+{
+ atomic64_add(count, &cma->nr_pages_succeeded);
+}
+
+void cma_sysfs_fail_pages_count(struct cma *cma, size_t count)
+{
+ atomic64_add(count, &cma->nr_pages_failed);
+}
+
+#define CMA_ATTR_RO(_name) \
+ static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
+
+static ssize_t alloc_pages_success_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct cma_kobject *cma_kobj = container_of(kobj,
+ struct cma_kobject, kobj);
+ struct cma *cma = cma_kobj->cma;
+
+ return sysfs_emit(buf, "%llu\n",
+ atomic64_read(&cma->nr_pages_succeeded));
+}
+CMA_ATTR_RO(alloc_pages_success);
+
+static ssize_t alloc_pages_fail_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct cma_kobject *cma_kobj = container_of(kobj,
+ struct cma_kobject, kobj);
+ struct cma *cma = cma_kobj->cma;
+
+ return sysfs_emit(buf, "%llu\n", atomic64_read(&cma->nr_pages_failed));
+}
+CMA_ATTR_RO(alloc_pages_fail);
+
+static void cma_kobj_release(struct kobject *kobj)
+{
+ struct cma_kobject *cma_kobj =
+ container_of(kobj, struct cma_kobject, kobj);
+ struct cma *cma = cma_kobj->cma;
+
+ kfree(cma_kobj);
+ cma->kobj = NULL;
+}
+
+static struct attribute *cma_attrs[] = {
+ &alloc_pages_success_attr.attr,
+ &alloc_pages_fail_attr.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(cma);
+
+static struct kobject *cma_kobj_root;
+
+static struct kobj_type cma_ktype = {
+ .release = cma_kobj_release,
+ .sysfs_ops = &kobj_sysfs_ops,
+ .default_groups = cma_groups
+};
+
+static int __init cma_sysfs_init(void)
+{
+ int i = 0;
+ struct cma *cma;
+
+ cma_kobj_root = kobject_create_and_add("cma", mm_kobj);
+ if (!cma_kobj_root)
+ return -ENOMEM;
+
+ for (i = 0; i < cma_area_count; i++) {
+ struct cma_kobject *kobj;
+
+ cma = &cma_areas[i];
+ kobj = kzalloc(sizeof(struct cma_kobject), GFP_KERNEL);
+ if (!kobj)
+ goto out;
+
+ kobj->cma = cma;
+ cma->kobj = kobj;
+ if (kobject_init_and_add(&cma->kobj->kobj, &cma_ktype,
+ cma_kobj_root, "%s", cma->name)) {
+ kobject_put(&cma->kobj->kobj);
+ goto out;
+ }
+ }
+
+ return 0;
+out:
+ kobject_put(cma_kobj_root);
+
+ return -ENOMEM;
+}
+subsys_initcall(cma_sysfs_init);
--
2.31.0.291.g576ba9dcdaf-goog