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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-03-25 19:39:37 +0100
committerIngo Molnar <mingo@elte.hu>2009-06-18 14:46:11 +0200
commit43a21ea81a2400992561146327c4785ce7f7be38 (patch)
treed4974c0ff9d7f40291515c5c0cf7e0d51abccb66 /include
parentd3a9262e59f7fb83c6d44df3b2b1460ed57d3ea1 (diff)
perf_counter: Add event overlow handling
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/perf_counter.h40
1 files changed, 28 insertions, 12 deletions
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index a7d3a61a59b..0765e8e6984 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -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)
@@ -275,6 +281,15 @@ enum perf_event_type {
/*
* struct {
+ * struct perf_event_header header;
+ * u64 id;
+ * u64 lost;
+ * };
+ */
+ PERF_EVENT_LOST = 2,
+
+ /*
+ * struct {
* struct perf_event_header header;
*
* u32 pid, tid;
@@ -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];