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Date: Wed, 10 Feb 2021 00:05:48 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Minchan Kim <minchan@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
CC: <willy@...radead.org>, <gregkh@...uxfoundation.org>,
<surenb@...gle.com>, <joaodias@...gle.com>,
LKML <linux-kernel@...r.kernel.org>,
linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v3] mm: cma: support sysfs
On 2/9/21 11:55 PM, Minchan Kim wrote:
> 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 allocation attempts
> * 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/cma_alloc_pages_[attempts|fails]
> /sys/kernel/mm/cma/SENSOR/cma_alloc_pages_[attempts|fails]
> /sys/kernel/mm/cma/BLUETOOTH/cma_alloc_pages_[attempts|fails]
>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
Looks good.
Reviewed-by: John Hubbard <jhubbard@...dia.com>
thanks,
--
John Hubbard
NVIDIA
> 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 | 6 +-
> mm/cma.h | 18 +++
> mm/cma_sysfs.c | 114 ++++++++++++++++++
> 6 files changed, 170 insertions(+), 1 deletion(-)
> 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..f518af819cee
> --- /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@...nel.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:
> +
> + cma_alloc_pages_attempts
> + cma_alloc_pages_fails
> +
> +What: /sys/kernel/mm/cma/<cma-heap-name>/cma_alloc_pages_attempts
> +Date: Feb 2021
> +Contact: Minchan Kim <minchan@...nel.org>
> +Description:
> + the number of pages CMA API tried to allocate
> +
> +What: /sys/kernel/mm/cma/<cma-heap-name>/cma_alloc_pages_fails
> +Date: Feb 2021
> +Contact: Minchan Kim <minchan@...nel.org>
> +Description:
> + the number of pages CMA API failed to allocate
> diff --git a/mm/Kconfig b/mm/Kconfig
> index ec35bf406439..ad7e9c065657 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 b2a564eec27f..e10c14300191 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 23d4a97c834a..b42ccafc71e5 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -447,9 +447,10 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> offset = cma_bitmap_aligned_offset(cma, align);
> bitmap_maxno = cma_bitmap_maxno(cma);
> bitmap_count = cma_bitmap_pages_to_bits(cma, count);
> + cma_sysfs_alloc_count(cma, count);
>
> if (bitmap_count > bitmap_maxno)
> - return NULL;
> + goto out;
>
> for (;;) {
> mutex_lock(&cma->lock);
> @@ -504,6 +505,9 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> __func__, count, ret);
> cma_debug_show_areas(cma);
> }
> +out:
> + if (!page)
> + cma_sysfs_fail_count(cma, count);
>
> pr_debug("%s(): returned %p\n", __func__, page);
> return page;
> diff --git a/mm/cma.h b/mm/cma.h
> index 42ae082cb067..24a1d61eabc7 100644
> --- a/mm/cma.h
> +++ b/mm/cma.h
> @@ -3,6 +3,14 @@
> #define __MM_CMA_H__
>
> #include <linux/debugfs.h>
> +#include <linux/kobject.h>
> +
> +struct cma_stat {
> + spinlock_t lock;
> + unsigned long pages_attempts; /* the number of CMA page allocation attempts */
> + unsigned long pages_fails; /* the number of CMA page allocation failures */
> + struct kobject kobj;
> +};
>
> struct cma {
> unsigned long base_pfn;
> @@ -16,6 +24,9 @@ struct cma {
> struct debugfs_u32_array dfs_bitmap;
> #endif
> char name[CMA_MAX_NAME];
> +#ifdef CONFIG_CMA_SYSFS
> + struct cma_stat *stat;
> +#endif
> };
>
> extern struct cma cma_areas[MAX_CMA_AREAS];
> @@ -26,4 +37,11 @@ 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_count(struct cma *cma, size_t count);
> +void cma_sysfs_fail_count(struct cma *cma, size_t count);
> +#else
> +static inline void cma_sysfs_alloc_count(struct cma *cma, size_t count) {};
> +static inline void cma_sysfs_fail_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..d281bf95a614
> --- /dev/null
> +++ b/mm/cma_sysfs.c
> @@ -0,0 +1,114 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * CMA SysFS Interface
> + *
> + * Copyright (c) 2021 Minchan Kim <minchan@...nel.org>
> + */
> +
> +#include <linux/cma.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +
> +#include "cma.h"
> +
> +static struct cma_stat *cma_stats;
> +
> +void cma_sysfs_alloc_count(struct cma *cma, size_t count)
> +{
> + spin_lock(&cma->stat->lock);
> + cma->stat->pages_attempts += count;
> + spin_unlock(&cma->stat->lock);
> +}
> +
> +void cma_sysfs_fail_count(struct cma *cma, size_t count)
> +{
> + spin_lock(&cma->stat->lock);
> + cma->stat->pages_fails += count;
> + spin_unlock(&cma->stat->lock);
> +}
> +
> +#define CMA_ATTR_RO(_name) \
> + static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
> +
> +static struct kobject *cma_kobj;
> +
> +static ssize_t cma_alloc_pages_attempts_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
> +
> + return sysfs_emit(buf, "%lu\n", stat->pages_attempts);
> +}
> +CMA_ATTR_RO(cma_alloc_pages_attempts);
> +
> +static ssize_t cma_alloc_pages_fails_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
> +
> + return sysfs_emit(buf, "%lu\n", stat->pages_fails);
> +}
> +CMA_ATTR_RO(cma_alloc_pages_fails);
> +
> +static void cma_kobj_release(struct kobject *kobj)
> +{
> + struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj);
> +
> + kfree(stat);
> +}
> +
> +static struct attribute *cma_attrs[] = {
> + &cma_alloc_pages_attempts_attr.attr,
> + &cma_alloc_pages_fails_attr.attr,
> + NULL,
> +};
> +ATTRIBUTE_GROUPS(cma);
> +
> +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 = kobject_create_and_add("cma", mm_kobj);
> + if (!cma_kobj) {
> + pr_err("failed to create cma kobject\n");
> + return -ENOMEM;
> + }
> +
> + cma_stats = kzalloc(array_size(sizeof(struct cma_stat),
> + cma_area_count), GFP_KERNEL);
> + if (!cma_stats) {
> + pr_err("failed to create cma_stats\n");
> + goto out;
> + }
> +
> + do {
> + cma = &cma_areas[i];
> + cma->stat = &cma_stats[i];
> + spin_lock_init(&cma->stat->lock);
> + if (kobject_init_and_add(&cma->stat->kobj, &cma_ktype,
> + cma_kobj, "%s", cma->name)) {
> + kobject_put(&cma->stat->kobj);
> + goto out;
> + }
> + } while (++i < cma_area_count);
> +
> + return 0;
> +out:
> + while (--i >= 0) {
> + cma = &cma_areas[i];
> + kobject_put(&cma->stat->kobj);
> + }
> +
> + kfree(cma_stats);
> + kobject_put(cma_kobj);
> +
> + return -ENOMEM;
> +}
> +subsys_initcall(cma_sysfs_init);
>
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