Messages in this thread Patch in this message | | | From | Borislav Petkov <> | Subject | [PATCH 1/2] perf: Add persistent event facilities | Date | Wed, 21 Mar 2012 15:34:55 +0100 |
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From: Borislav Petkov <borislav.petkov@amd.com>
Add a barebones implementation for registering persistent events with perf. For that, we don't destroy the buffers when they're unmapped; also, we map them read-only so that multiple agents can access them.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com> --- include/linux/perf_event.h | 24 ++++++++++- kernel/events/Makefile | 2 +- kernel/events/core.c | 25 +++++++++-- kernel/events/internal.h | 2 + kernel/events/persistent.c | 98 ++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 145 insertions(+), 6 deletions(-) create mode 100644 kernel/events/persistent.c
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index abb2776be1ba..9743ba46e12d 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -223,8 +223,9 @@ struct perf_event_attr { exclude_host : 1, /* don't count in host */ exclude_guest : 1, /* don't count in guest */ + persistent : 1, /* always-on event */ - __reserved_1 : 43; + __reserved_1 : 42; union { __u32 wakeup_events; /* wakeup every n events */ @@ -944,6 +945,14 @@ struct perf_output_handle { int page; }; +/* Persistent events descriptor */ +struct pers_event_desc { + struct perf_event_attr *pattr; + struct perf_event *event; + const char *dfs_name; + struct dentry *dfs_entry; +}; + #ifdef CONFIG_PERF_EVENTS extern int perf_pmu_register(struct pmu *pmu, char *name, int type); @@ -1149,6 +1158,11 @@ extern void perf_swevent_put_recursion_context(int rctx); extern void perf_event_enable(struct perf_event *event); extern void perf_event_disable(struct perf_event *event); extern void perf_event_task_tick(void); +extern int perf_add_persistent_on_cpu(int cpu, struct pers_event_desc *desc, + struct dentry *dfs_dr, unsigned nr_pages); +extern void perf_rm_persistent_on_cpu(int cpu, struct pers_event_desc *desc); +extern int perf_persistent_open(struct inode *inode, struct file *file); +extern const struct file_operations perf_pers_fops; #else static inline void perf_event_task_sched_in(struct task_struct *prev, @@ -1187,6 +1201,14 @@ static inline void perf_swevent_put_recursion_context(int rctx) { } static inline void perf_event_enable(struct perf_event *event) { } static inline void perf_event_disable(struct perf_event *event) { } static inline void perf_event_task_tick(void) { } +extern int perf_add_persistent_on_cpu(int cpu, struct pers_event_desc *desc, + struct perf_event_attr *pattr, + struct dentry *dfs_dir, + unsigned nr_pages); { return -EINVAL; } +extern void perf_rm_persistent_on_cpu(int cpu, + struct pers_event_desc *desc) { } +static inline int +perf_persistent_open(struct inode *inode, struct file *file) { return -1; } #endif #define perf_output_put(handle, x) perf_output_copy((handle), &(x), sizeof(x)) diff --git a/kernel/events/Makefile b/kernel/events/Makefile index 22d901f9caf4..0d2267fb4336 100644 --- a/kernel/events/Makefile +++ b/kernel/events/Makefile @@ -2,5 +2,5 @@ ifdef CONFIG_FUNCTION_TRACER CFLAGS_REMOVE_core.o = -pg endif -obj-y := core.o ring_buffer.o callchain.o +obj-y := core.o ring_buffer.o callchain.o persistent.o obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o diff --git a/kernel/events/core.c b/kernel/events/core.c index 1b5c081d8b9f..9a39dc6755f4 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2770,8 +2770,6 @@ static void free_event_rcu(struct rcu_head *head) kfree(event); } -static void ring_buffer_put(struct ring_buffer *rb); - static void free_event(struct perf_event *event) { irq_work_sync(&event->pending); @@ -3423,7 +3421,7 @@ static struct ring_buffer *ring_buffer_get(struct perf_event *event) return rb; } -static void ring_buffer_put(struct ring_buffer *rb) +void ring_buffer_put(struct ring_buffer *rb) { struct perf_event *event, *n; unsigned long flags; @@ -3452,6 +3450,11 @@ static void perf_mmap_close(struct vm_area_struct *vma) { struct perf_event *event = vma->vm_file->private_data; + if (event->attr.persistent) { + atomic_dec(&event->mmap_count); + return; + } + if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) { unsigned long size = perf_data_size(event->rb); struct user_struct *user = event->mmap_user; @@ -3495,7 +3498,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) if (event->cpu == -1 && event->attr.inherit) return -EINVAL; - if (!(vma->vm_flags & VM_SHARED)) + if (!(vma->vm_flags & VM_SHARED) && !event->attr.persistent) return -EINVAL; vma_size = vma->vm_end - vma->vm_start; @@ -3606,6 +3609,16 @@ static const struct file_operations perf_fops = { .fasync = perf_fasync, }; +const struct file_operations perf_pers_fops = { + .llseek = no_llseek, + .open = perf_persistent_open, + .poll = perf_poll, + .unlocked_ioctl = perf_ioctl, + .compat_ioctl = perf_ioctl, + .mmap = perf_mmap, + .fasync = perf_fasync, +}; + /* * Perf event wakeup * @@ -6319,6 +6332,10 @@ __perf_event_exit_task(struct perf_event *child_event, raw_spin_unlock_irq(&child_ctx->lock); } + /* do not remove persistent events on task exit */ + if (child_event->attr.persistent) + return; + perf_remove_from_context(child_event); /* diff --git a/kernel/events/internal.h b/kernel/events/internal.h index b0b107f90afc..d4e6181d5faf 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -37,6 +37,8 @@ struct ring_buffer { extern void rb_free(struct ring_buffer *rb); extern struct ring_buffer * rb_alloc(int nr_pages, long watermark, int cpu, int flags); +extern void ring_buffer_put(struct ring_buffer *rb); + extern void perf_event_wakeup(struct perf_event *event); extern void diff --git a/kernel/events/persistent.c b/kernel/events/persistent.c new file mode 100644 index 000000000000..e6f146532e34 --- /dev/null +++ b/kernel/events/persistent.c @@ -0,0 +1,98 @@ +#include <linux/debugfs.h> +#include <linux/perf_event.h> + +#include "internal.h" + +/* + * Create and enable the perf event described by @attr. + * + * Returns the @event pointer which receives the allocated event from + * perf on success. Make sure to check return code before touching @event + * any further. + * + * @attr: perf attr template + * @cpu: on which cpu + * @nr_pages: perf buffer size in pages + * + */ +static struct perf_event *perf_add_persistent(struct perf_event_attr *attr, + int cpu, unsigned nr_pages) +{ + struct ring_buffer *buffer; + struct perf_event *event; + + event = perf_event_create_kernel_counter(attr, cpu, NULL, NULL, NULL); + if (IS_ERR(event)) + return event; + + buffer = rb_alloc(nr_pages, 0, cpu, RING_BUFFER_WRITABLE); + if (!buffer) + goto err; + + rcu_assign_pointer(event->rb, buffer); + perf_event_enable(event); + + return event; + +err: + perf_event_release_kernel(event); + return ERR_PTR(-EINVAL); +} + +static void perf_rm_persistent(struct perf_event *event, int cpu) +{ + if (!event) + return; + + perf_event_disable(event); + + if (event->rb) { + ring_buffer_put(event->rb); + rcu_assign_pointer(event->rb, NULL); + } + + perf_event_release_kernel(event); +} + +static struct dentry *perf_add_debugfs_entry(struct pers_event_desc *d, + struct dentry *dir) +{ + return debugfs_create_file(d->dfs_name, S_IRUGO | S_IWUSR, + dir, d->event, &perf_pers_fops); +} + +int perf_add_persistent_on_cpu(int cpu, struct pers_event_desc *desc, + struct dentry *dir, unsigned nr_pages) +{ + int err = -EINVAL; + + desc->event = perf_add_persistent(desc->pattr, cpu, nr_pages); + if (IS_ERR(desc->event)) { + printk(KERN_ERR "Error enabling persistent event on cpu %d\n", cpu); + return err; + } + + desc->dfs_entry = perf_add_debugfs_entry(desc, dir); + if (!desc->dfs_entry) { + printk(KERN_ERR "Error adding debugfs entry on cpu %d\n", cpu); + goto disable; + } + return 0; + +disable: + perf_rm_persistent(desc->event, cpu); + return err; +} + +void perf_rm_persistent_on_cpu(int cpu, struct pers_event_desc *desc) +{ + debugfs_remove(desc->dfs_entry); + perf_rm_persistent(desc->event, cpu); +} + +int perf_persistent_open(struct inode *inode, struct file *file) +{ + file->private_data = inode->i_private; + + return 0; +} -- 1.7.9.3.362.g71319
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