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This patch modifies the perf tool to handle the new RECORD type,
PERF_RECORD_LOST_SAMPLES.
The number of lost-sample events is stored in
.nr_events[PERF_RECORD_LOST_SAMPLES]. The exact number of samples
which the kernel dropped is stored in total_lost_samples.
When the percentage of dropped samples is greater than 5%, a warning
is printed.
Here are some examples:
Eg 1, Recording different frequently-occurring events is safe with the
patch. Only a very low drop rate is associated with such actions.
$ perf record -e '{cycles:p,instructions:p}' -c 20003 --no-time ~/tchain ~/tchain
$ perf report -D | tail
SAMPLE events: 120243
MMAP2 events: 5
LOST_SAMPLES events: 24
FINISHED_ROUND events: 15
cycles:p stats:
TOTAL events: 59348
SAMPLE events: 59348
instructions:p stats:
TOTAL events: 60895
SAMPLE events: 60895
$ perf report --stdio --group
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 24
#
# Samples: 120K of event 'anon group { cycles:p, instructions:p }'
# Event count (approx.): 24048600000
#
# Overhead Command Shared Object Symbol
# ................ ........... ................
..................................
#
99.74% 99.86% tchain_edit tchain_edit [.] f3
0.09% 0.02% tchain_edit tchain_edit [.] f2
0.04% 0.00% tchain_edit [kernel.vmlinux] [k] ixgbe_read_reg
Eg 2, Recording the same thing multiple times can lead to high drop
rate, but it is not a useful configuration.
$ perf record -e '{cycles:p,cycles:p}' -c 20003 --no-time ~/tchain
Warning: Processed 600592 samples and lost 99.73% samples!
[perf record: Woken up 148 times to write data]
[perf record: Captured and wrote 36.922 MB perf.data (1206322 samples)]
[perf record: Woken up 1 times to write data]
[perf record: Captured and wrote 0.121 MB perf.data (1629 samples)]
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1431285195-14269-9-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
64 lines
1.4 KiB
C
64 lines
1.4 KiB
C
#ifndef __PERF_TOOL_H
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#define __PERF_TOOL_H
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#include <stdbool.h>
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#include <linux/types.h>
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struct perf_session;
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union perf_event;
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struct perf_evlist;
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struct perf_evsel;
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struct perf_sample;
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struct perf_tool;
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struct machine;
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struct ordered_events;
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typedef int (*event_sample)(struct perf_tool *tool, union perf_event *event,
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struct perf_sample *sample,
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struct perf_evsel *evsel, struct machine *machine);
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typedef int (*event_op)(struct perf_tool *tool, union perf_event *event,
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struct perf_sample *sample, struct machine *machine);
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typedef int (*event_attr_op)(struct perf_tool *tool,
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union perf_event *event,
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struct perf_evlist **pevlist);
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typedef int (*event_op2)(struct perf_tool *tool, union perf_event *event,
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struct perf_session *session);
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typedef int (*event_oe)(struct perf_tool *tool, union perf_event *event,
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struct ordered_events *oe);
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typedef s64 (*event_op3)(struct perf_tool *tool, union perf_event *event,
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struct perf_session *session);
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struct perf_tool {
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event_sample sample,
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read;
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event_op mmap,
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mmap2,
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comm,
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fork,
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exit,
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lost,
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lost_samples,
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aux,
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itrace_start,
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throttle,
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unthrottle;
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event_attr_op attr;
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event_op2 tracing_data;
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event_oe finished_round;
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event_op2 build_id,
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id_index,
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auxtrace_info,
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auxtrace_error;
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event_op3 auxtrace;
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bool ordered_events;
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bool ordering_requires_timestamps;
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};
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#endif /* __PERF_TOOL_H */
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