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perf events: Precalculate the header space for PERF_SAMPLE_ fields
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PERF_SAMPLE_{CALLCHAIN,RAW} have variable lenghts per sample, but the others
can be precalculated, reducing a bit the per sample cost.

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Ian Munsie <imunsie@au1.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Arnaldo Carvalho de Melo committed Nov 30, 2010
1 parent 068ffaa commit c320c7b
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Showing 2 changed files with 93 additions and 59 deletions.
2 changes: 2 additions & 0 deletions include/linux/perf_event.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -758,6 +758,8 @@ struct perf_event {
u64 shadow_ctx_time;

struct perf_event_attr attr;
u16 header_size;
u16 read_size;
struct hw_perf_event hw;

struct perf_event_context *ctx;
Expand Down
150 changes: 91 additions & 59 deletions kernel/perf_event.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -312,9 +312,75 @@ list_add_event(struct perf_event *event, struct perf_event_context *ctx)
ctx->nr_stat++;
}

/*
* Called at perf_event creation and when events are attached/detached from a
* group.
*/
static void perf_event__read_size(struct perf_event *event)
{
int entry = sizeof(u64); /* value */
int size = 0;
int nr = 1;

if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
size += sizeof(u64);

if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
size += sizeof(u64);

if (event->attr.read_format & PERF_FORMAT_ID)
entry += sizeof(u64);

if (event->attr.read_format & PERF_FORMAT_GROUP) {
nr += event->group_leader->nr_siblings;
size += sizeof(u64);
}

size += entry * nr;
event->read_size = size;
}

static void perf_event__header_size(struct perf_event *event)
{
struct perf_sample_data *data;
u64 sample_type = event->attr.sample_type;
u16 size = 0;

perf_event__read_size(event);

if (sample_type & PERF_SAMPLE_IP)
size += sizeof(data->ip);

if (sample_type & PERF_SAMPLE_TID)
size += sizeof(data->tid_entry);

if (sample_type & PERF_SAMPLE_TIME)
size += sizeof(data->time);

if (sample_type & PERF_SAMPLE_ADDR)
size += sizeof(data->addr);

if (sample_type & PERF_SAMPLE_ID)
size += sizeof(data->id);

if (sample_type & PERF_SAMPLE_STREAM_ID)
size += sizeof(data->stream_id);

if (sample_type & PERF_SAMPLE_CPU)
size += sizeof(data->cpu_entry);

if (sample_type & PERF_SAMPLE_PERIOD)
size += sizeof(data->period);

if (sample_type & PERF_SAMPLE_READ)
size += event->read_size;

event->header_size = size;
}

static void perf_group_attach(struct perf_event *event)
{
struct perf_event *group_leader = event->group_leader;
struct perf_event *group_leader = event->group_leader, *pos;

/*
* We can have double attach due to group movement in perf_event_open.
Expand All @@ -333,6 +399,11 @@ static void perf_group_attach(struct perf_event *event)

list_add_tail(&event->group_entry, &group_leader->sibling_list);
group_leader->nr_siblings++;

perf_event__header_size(group_leader);

list_for_each_entry(pos, &group_leader->sibling_list, group_entry)
perf_event__header_size(pos);
}

/*
Expand Down Expand Up @@ -391,7 +462,7 @@ static void perf_group_detach(struct perf_event *event)
if (event->group_leader != event) {
list_del_init(&event->group_entry);
event->group_leader->nr_siblings--;
return;
goto out;
}

if (!list_empty(&event->group_entry))
Expand All @@ -410,6 +481,12 @@ static void perf_group_detach(struct perf_event *event)
/* Inherit group flags from the previous leader */
sibling->group_flags = event->group_flags;
}

out:
perf_event__header_size(event->group_leader);

list_for_each_entry(tmp, &event->group_leader->sibling_list, group_entry)
perf_event__header_size(tmp);
}

static inline int
Expand Down Expand Up @@ -2289,31 +2366,6 @@ static int perf_release(struct inode *inode, struct file *file)
return perf_event_release_kernel(event);
}

static int perf_event_read_size(struct perf_event *event)
{
int entry = sizeof(u64); /* value */
int size = 0;
int nr = 1;

if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
size += sizeof(u64);

if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
size += sizeof(u64);

if (event->attr.read_format & PERF_FORMAT_ID)
entry += sizeof(u64);

if (event->attr.read_format & PERF_FORMAT_GROUP) {
nr += event->group_leader->nr_siblings;
size += sizeof(u64);
}

size += entry * nr;

return size;
}

u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
{
struct perf_event *child;
Expand Down Expand Up @@ -2428,7 +2480,7 @@ perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
if (event->state == PERF_EVENT_STATE_ERROR)
return 0;

if (count < perf_event_read_size(event))
if (count < event->read_size)
return -ENOSPC;

WARN_ON_ONCE(event->ctx->parent_ctx);
Expand Down Expand Up @@ -3606,59 +3658,34 @@ void perf_prepare_sample(struct perf_event_header *header,
data->type = sample_type;

header->type = PERF_RECORD_SAMPLE;
header->size = sizeof(*header);
header->size = sizeof(*header) + event->header_size;

header->misc = 0;
header->misc |= perf_misc_flags(regs);

if (sample_type & PERF_SAMPLE_IP) {
if (sample_type & PERF_SAMPLE_IP)
data->ip = perf_instruction_pointer(regs);

header->size += sizeof(data->ip);
}

if (sample_type & PERF_SAMPLE_TID) {
/* namespace issues */
data->tid_entry.pid = perf_event_pid(event, current);
data->tid_entry.tid = perf_event_tid(event, current);

header->size += sizeof(data->tid_entry);
}

if (sample_type & PERF_SAMPLE_TIME) {
if (sample_type & PERF_SAMPLE_TIME)
data->time = perf_clock();

header->size += sizeof(data->time);
}

if (sample_type & PERF_SAMPLE_ADDR)
header->size += sizeof(data->addr);

if (sample_type & PERF_SAMPLE_ID) {
if (sample_type & PERF_SAMPLE_ID)
data->id = primary_event_id(event);

header->size += sizeof(data->id);
}

if (sample_type & PERF_SAMPLE_STREAM_ID) {
if (sample_type & PERF_SAMPLE_STREAM_ID)
data->stream_id = event->id;

header->size += sizeof(data->stream_id);
}

if (sample_type & PERF_SAMPLE_CPU) {
data->cpu_entry.cpu = raw_smp_processor_id();
data->cpu_entry.reserved = 0;

header->size += sizeof(data->cpu_entry);
}

if (sample_type & PERF_SAMPLE_PERIOD)
header->size += sizeof(data->period);

if (sample_type & PERF_SAMPLE_READ)
header->size += perf_event_read_size(event);

if (sample_type & PERF_SAMPLE_CALLCHAIN) {
int size = 1;

Expand Down Expand Up @@ -3726,7 +3753,7 @@ perf_event_read_event(struct perf_event *event,
.header = {
.type = PERF_RECORD_READ,
.misc = 0,
.size = sizeof(read_event) + perf_event_read_size(event),
.size = sizeof(read_event) + event->read_size,
},
.pid = perf_event_pid(event, task),
.tid = perf_event_tid(event, task),
Expand Down Expand Up @@ -5714,6 +5741,11 @@ SYSCALL_DEFINE5(perf_event_open,
list_add_tail(&event->owner_entry, &current->perf_event_list);
mutex_unlock(&current->perf_event_mutex);

/*
* Precalculate sample_data sizes
*/
perf_event__header_size(event);

/*
* Drop the reference on the group_event after placing the
* new event on the sibling_list. This ensures destruction
Expand Down

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