8d06367fa7
With this change 'perf record' will intercept PERF_RECORD_MMAP
calls, creating a linked list of DSOs, then when the session
finishes, it will traverse this list and read the buildids,
stashing them at the end of the file and will set up a new
feature bit in the header bitmask.
'perf report' will then notice this feature and populate the
'dsos' list and set the build ids.
When reading the symtabs it will refuse to load from a file that
doesn't have the same build id. This improves the
reliability of the profiler output, as symbols and profiling
data is more guaranteed to match.
Example:
[root@doppio ~]# perf report | head
/home/acme/bin/perf with build id b1ea544ac3746e7538972548a09aadecc5753868 not found, continuing without symbols
# Samples: 2621434559
#
# Overhead Command Shared Object Symbol
# ........ ............... ............................. ......
#
7.91% init [kernel] [k] read_hpet
7.64% init [kernel] [k] mwait_idle_with_hints
7.60% swapper [kernel] [k] read_hpet
7.60% swapper [kernel] [k] mwait_idle_with_hints
3.65% init [kernel] [k] 0xffffffffa02339d9
[root@doppio ~]#
In this case the 'perf' binary was an older one, vanished,
so its symbols probably wouldn't match or would cause subtly
different (and misleading) output.
Next patches will support the kernel as well, reading the build
id notes for it and the modules from /sys.
Another patch should also introduce a new plumbing command:
'perf list-buildids'
that will then be used in porcelain that is distro specific to
fetch -debuginfo packages where such buildids are present. This
will in turn allow for one to run 'perf record' in one machine
and 'perf report' in another.
Future work on having the buildid sent directly from the kernel
in the PERF_RECORD_MMAP event is needed to close races, as the
DSO can be changed during a 'perf record' session, but this
patch at least helps with non-corner cases and current/older
kernels.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: K. Prasad <prasad@linux.vnet.ibm.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1257367843-26224-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
58 lines
1.5 KiB
C
58 lines
1.5 KiB
C
#ifndef __PERF_HEADER_H
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#define __PERF_HEADER_H
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#include "../../../include/linux/perf_event.h"
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#include <sys/types.h>
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#include <stdbool.h>
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#include "types.h"
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#include <linux/bitmap.h>
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struct perf_header_attr {
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struct perf_event_attr attr;
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int ids, size;
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u64 *id;
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off_t id_offset;
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};
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#define HEADER_TRACE_INFO 1
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#define HEADER_BUILD_ID 2
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#define HEADER_FEAT_BITS 256
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struct perf_header {
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int frozen;
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int attrs, size;
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struct perf_header_attr **attr;
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s64 attr_offset;
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u64 data_offset;
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u64 data_size;
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u64 event_offset;
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u64 event_size;
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DECLARE_BITMAP(adds_features, HEADER_FEAT_BITS);
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};
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struct perf_header *perf_header__read(int fd);
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void perf_header__write(struct perf_header *self, int fd);
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void perf_header__add_attr(struct perf_header *self,
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struct perf_header_attr *attr);
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void perf_header__push_event(u64 id, const char *name);
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char *perf_header__find_event(u64 id);
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struct perf_header_attr *
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perf_header_attr__new(struct perf_event_attr *attr);
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void perf_header_attr__add_id(struct perf_header_attr *self, u64 id);
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u64 perf_header__sample_type(struct perf_header *header);
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struct perf_event_attr *
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perf_header__find_attr(u64 id, struct perf_header *header);
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void perf_header__feat_trace_info(struct perf_header *header);
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void perf_header__set_feat(struct perf_header *self, int feat);
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bool perf_header__has_feat(const struct perf_header *self, int feat);
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struct perf_header *perf_header__new(void);
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#endif /* __PERF_HEADER_H */
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