| Message ID | 20210303205053.2906924-1-minchan@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] mm: cma: support sysfs | expand |
On Wed, 3 Mar 2021 12:50:53 -0800 Minchan Kim <minchan@kernel.org> 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] > > ... > > --- 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 > }; Why aren't the stat fields simply placed directly into struct cma_stat? > ... > > +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); kmalloc_array(..., GFP_KERNEL|__GFP_ZERO); ? > + if (!cma_stats) { > + pr_err("failed to create cma_stats\n"); Probably unneeded - the ENOMEM stack backtrace will point straight here. > + 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);
On Wed, Mar 03, 2021 at 02:44:49PM -0800, Andrew Morton wrote: > On Wed, 3 Mar 2021 12:50:53 -0800 Minchan Kim <minchan@kernel.org> 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] > > > > ... > > > > --- 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 > > }; > > Why aren't the stat fields simply placed directly into struct cma_stat? It have a related long discussion. https://lore.kernel.org/linux-mm/YCIoHBGELFWAyfMi@kroah.com/ https://lore.kernel.org/linux-mm/YCLLKDEQ4NYqb5Y5@kroah.com/ TLDR - Greg really want to see kobject stuff working as dynamic property. > > > ... > > > > +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); > > kmalloc_array(..., GFP_KERNEL|__GFP_ZERO); Yub. > > ? > > > + if (!cma_stats) { > > + pr_err("failed to create cma_stats\n"); > > Probably unneeded - the ENOMEM stack backtrace will point straight here. I failed to find the point you mentioned to print backtrace. Where code do you mean to dump the backtrace?
On Wed, 3 Mar 2021 17:38:12 -0800 Minchan Kim <minchan@kernel.org> wrote: > > > #endif > > > char name[CMA_MAX_NAME]; > > > +#ifdef CONFIG_CMA_SYSFS > > > + struct cma_stat *stat; > > > +#endif > > > }; > > > > Why aren't the stat fields simply placed directly into struct cma_stat? > > It have a related long discussion. > https://lore.kernel.org/linux-mm/YCIoHBGELFWAyfMi@kroah.com/ > https://lore.kernel.org/linux-mm/YCLLKDEQ4NYqb5Y5@kroah.com/ > > TLDR - Greg really want to see kobject stuff working as dynamic > property. Please add to changelog? > > > > ? > > > > > + if (!cma_stats) { > > > + pr_err("failed to create cma_stats\n"); > > > > Probably unneeded - the ENOMEM stack backtrace will point straight here. > > I failed to find the point you mentioned to print backtrace. > Where code do you mean to dump the backtrace? The thing which __GFP_NOWARN disables.
On Wed, Mar 03, 2021 at 10:09:57PM -0800, Andrew Morton wrote: > On Wed, 3 Mar 2021 17:38:12 -0800 Minchan Kim <minchan@kernel.org> wrote: > > > > > #endif > > > > char name[CMA_MAX_NAME]; > > > > +#ifdef CONFIG_CMA_SYSFS > > > > + struct cma_stat *stat; > > > > +#endif > > > > }; > > > > > > Why aren't the stat fields simply placed directly into struct cma_stat? > > > > It have a related long discussion. > > https://lore.kernel.org/linux-mm/YCIoHBGELFWAyfMi@kroah.com/ > > https://lore.kernel.org/linux-mm/YCLLKDEQ4NYqb5Y5@kroah.com/ > > > > TLDR - Greg really want to see kobject stuff working as dynamic > > property. > > Please add to changelog? Sure. > > > > > > > ? > > > > > > > + if (!cma_stats) { > > > > + pr_err("failed to create cma_stats\n"); > > > > > > Probably unneeded - the ENOMEM stack backtrace will point straight here. > > > > I failed to find the point you mentioned to print backtrace. > > Where code do you mean to dump the backtrace? > > The thing which __GFP_NOWARN disables. Got the point.
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@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: + + 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@kernel.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@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 54eee2119822..551b704faeaf 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__, cma->name, 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@kernel.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);