When AUX area gets a certain amount of new data, we want to wake up
userspace to collect it. This adds a new control to specify how much
data will cause a wakeup. This is then passed down to pmu drivers via
output handle's "wakeup" field, so that the driver can find the nearest
point where it can generate an interrupt.
We repurpose __reserved_2 in the event attribute for this, even though
it was never checked to be zero before, aux_watermark will only matter
for new AUX-aware code, so the old code should still be fine.
Signed-off-by: Alexander Shishkin <alexander.shish...@linux.intel.com>
---
include/uapi/linux/perf_event.h | 8 ++++++--
kernel/events/core.c | 3 ++-
kernel/events/internal.h | 4 +++-
kernel/events/ring_buffer.c | 22 +++++++++++++++++++---
4 files changed, 30 insertions(+), 7 deletions(-)
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index c10b9297cb..143d961857 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -240,6 +240,7 @@ enum perf_event_read_format {
#define PERF_ATTR_SIZE_VER3 96 /* add: sample_regs_user */
/* add: sample_stack_user */
#define PERF_ATTR_SIZE_VER4 104 /* add: sample_regs_intr */
+ /* add: aux_watermark */
/*
* Hardware event_id to monitor via a performance monitoring event:
@@ -334,8 +335,11 @@ struct perf_event_attr {
*/
__u32 sample_stack_user;
- /* Align to u64. */
- __u32 __reserved_2;
+ /*
+ * Wakeup watermark for AUX area
+ */
+ __u32 aux_watermark;
+
/*
* Defines set of regs to dump for each sample
* state captured on:
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6a29f9ac5f..a7f3eec481 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4421,7 +4421,8 @@ accounting:
perf_event_init_userpage(event);
perf_event_update_userpage(event);
} else {
- ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages, flags);
+ ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages,
+ event->attr.aux_watermark, flags);
if (!ret)
rb->aux_mmap_locked = extra;
}
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index ffd51d9f59..9f6ce9ba4a 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -27,6 +27,7 @@ struct ring_buffer {
local_t lost; /* nr records lost */
long watermark; /* wakeup watermark */
+ long aux_watermark;
/* poll crap */
spinlock_t event_lock;
struct list_head event_list;
@@ -38,6 +39,7 @@ struct ring_buffer {
/* AUX area */
local_t aux_head;
local_t aux_nest;
+ local_t aux_wakeup;
unsigned long aux_pgoff;
int aux_nr_pages;
int aux_overwrite;
@@ -57,7 +59,7 @@ extern struct ring_buffer *
rb_alloc(int nr_pages, long watermark, int cpu, int flags);
extern void perf_event_wakeup(struct perf_event *event);
extern int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
- pgoff_t pgoff, int nr_pages, int flags);
+ pgoff_t pgoff, int nr_pages, long watermark, int flags);
extern void rb_free_aux(struct ring_buffer *rb);
extern struct ring_buffer *ring_buffer_get(struct perf_event *event);
extern void ring_buffer_put(struct ring_buffer *rb);
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 8bff8c85eb..8d959f24ab 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -295,6 +295,7 @@ void *perf_aux_output_begin(struct perf_output_handle
*handle,
*/
if (!rb->aux_overwrite) {
aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);
+ handle->wakeup = local_read(&rb->aux_wakeup) +
rb->aux_watermark;
if (aux_head - aux_tail < perf_aux_size(rb))
handle->size = CIRC_SPACE(aux_head, aux_tail,
perf_aux_size(rb));
@@ -358,9 +359,12 @@ void perf_aux_output_end(struct perf_output_handle
*handle, unsigned long size,
perf_event_aux_event(handle->event, aux_head, size, flags);
}
- rb->user_page->aux_head = local_read(&rb->aux_head);
+ aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
- perf_output_wakeup(handle);
+ if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ perf_output_wakeup(handle);
+ local_add(rb->aux_watermark, &rb->aux_wakeup);
+ }
handle->event = NULL;
local_set(&rb->aux_nest, 0);
@@ -382,6 +386,14 @@ int perf_aux_output_skip(struct perf_output_handle
*handle, unsigned long size)
local_add(size, &rb->aux_head);
+ aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
+ if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ perf_output_wakeup(handle);
+ local_add(rb->aux_watermark, &rb->aux_wakeup);
+ handle->wakeup = local_read(&rb->aux_wakeup) +
+ rb->aux_watermark;
+ }
+
handle->head = aux_head;
handle->size -= size;
@@ -432,7 +444,7 @@ static void rb_free_aux_page(struct ring_buffer *rb, int
idx)
}
int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
- pgoff_t pgoff, int nr_pages, int flags)
+ pgoff_t pgoff, int nr_pages, long watermark, int flags)
{
bool overwrite = !(flags & RING_BUFFER_WRITABLE);
int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
@@ -496,6 +508,10 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event
*event,
atomic_set(&rb->aux_refcount, 1);
rb->aux_overwrite = overwrite;
+ rb->aux_watermark = watermark;
+
+ if (!rb->aux_watermark && !rb->aux_overwrite)
+ rb->aux_watermark = nr_pages << (PAGE_SHIFT - 1);
out:
if (!ret)
--
2.1.4
--
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