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perf_counter: Add event overlow handling

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Alternative method of mmap() data output handling that provides
better overflow management and a more reliable data stream.

Unlike the previous method, that didn't have any user->kernel
feedback and relied on userspace keeping up, this method relies on
userspace writing its last read position into the control page.

It will ensure new output doesn't overwrite not-yet read events,
new events for which there is no space left are lost and the
overflow counter is incremented, providing exact event loss
numbers.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2009-03-25 19:39:37 +01:00 • committed by Ingo Molnar
parent d3a9262e59
commit 43a21ea81a
2 changed files with 162 additions and 71 deletions
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40
include/linux/perf_counter.h
View file

@ -236,10 +236,16 @@ struct perf_counter_mmap_page {
/*
* Control data for the mmap() data buffer.
*
* User-space reading this value should issue an rmb(), on SMP capable
* platforms, after reading this value -- see perf_counter_wakeup().
* User-space reading the @data_head value should issue an rmb(), on
* SMP capable platforms, after reading this value -- see
* perf_counter_wakeup().
*
* When the mapping is PROT_WRITE the @data_tail value should be
* written by userspace to reflect the last read data. In this case
* the kernel will not over-write unread data.
*/
__u64 data_head; /* head in the data section */
__u64 data_tail; /* user-space written tail */
};
#define PERF_EVENT_MISC_CPUMODE_MASK (3 << 0)
@ -273,6 +279,15 @@ enum perf_event_type {
*/
PERF_EVENT_MMAP = 1,
/*
* struct {
* struct perf_event_header header;
* u64 id;
* u64 lost;
* };
*/
PERF_EVENT_LOST = 2,
/*
* struct {
* struct perf_event_header header;
@ -313,26 +328,26 @@ enum perf_event_type {
/*
* When header.misc & PERF_EVENT_MISC_OVERFLOW the event_type field
* will be PERF_RECORD_*
* will be PERF_SAMPLE_*
*
* struct {
* struct perf_event_header header;
*
* { u64 ip; } && PERF_RECORD_IP
* { u32 pid, tid; } && PERF_RECORD_TID
* { u64 time; } && PERF_RECORD_TIME
* { u64 addr; } && PERF_RECORD_ADDR
* { u64 config; } && PERF_RECORD_CONFIG
* { u32 cpu, res; } && PERF_RECORD_CPU
* { u64 ip; } && PERF_SAMPLE_IP
* { u32 pid, tid; } && PERF_SAMPLE_TID
* { u64 time; } && PERF_SAMPLE_TIME
* { u64 addr; } && PERF_SAMPLE_ADDR
* { u64 config; } && PERF_SAMPLE_CONFIG
* { u32 cpu, res; } && PERF_SAMPLE_CPU
*
* { u64 nr;
* { u64 id, val; } cnt[nr]; } && PERF_RECORD_GROUP
* { u64 id, val; } cnt[nr]; } && PERF_SAMPLE_GROUP
*
* { u16 nr,
* hv,
* kernel,
* user;
* u64 ips[nr]; } && PERF_RECORD_CALLCHAIN
* u64 ips[nr]; } && PERF_SAMPLE_CALLCHAIN
* };
*/
};
@ -424,6 +439,7 @@ struct file;
struct perf_mmap_data {
struct rcu_head rcu_head;
int nr_pages; /* nr of data pages */
int writable; /* are we writable */
int nr_locked; /* nr pages mlocked */
atomic_t poll; /* POLL_ for wakeups */
@ -433,8 +449,8 @@ struct perf_mmap_data {
atomic_long_t done_head; /* completed head */
atomic_t lock; /* concurrent writes */
atomic_t wakeup; /* needs a wakeup */
atomic_t lost; /* nr records lost */
struct perf_counter_mmap_page *user_page;
void *data_pages[0];