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+perf.data directory format
+
+DISCLAIMER This is not ABI yet and is subject to possible change
+ in following versions of perf. We will remove this
+ disclaimer once the directory format soaks in.
+
+
+This document describes the on-disk perf.data directory format.
+
+The layout is described by HEADER_DIR_FORMAT feature.
+Currently it holds only version number (0):
+
+ HEADER_DIR_FORMAT = 24
+
+ struct {
+ uint64_t version;
+ }
+
+The current only version value 0 means that:
+ - there is a single perf.data file named 'data' within the directory.
+ e.g.
+
+ $ tree -ps perf.data
+ perf.data
+ └── [-rw------- 25912] data
+
+Future versions are expected to describe different data files
+layout according to special needs.
+
+Currently the only 'perf record' option to output to a directory is
+the --kcore option which puts a copy of /proc/kcore into the directory.
+e.g.
+
+ $ sudo perf record --kcore uname
+ Linux
+ [ perf record: Woken up 1 times to write data ]
+ [ perf record: Captured and wrote 0.015 MB perf.data (9 samples) ]
+ $ sudo tree -ps perf.data
+ perf.data
+ ├── [-rw------- 23744] data
+ └── [drwx------ 4096] kcore_dir
+ ├── [-r-------- 6731125] kallsyms
+ ├── [-r-------- 40230912] kcore
+ └── [-r-------- 5419] modules
+
+ 1 directory, 4 files
+ $ sudo perf script -v
+ build id event received for vmlinux: 1eaa285996affce2d74d8e66dcea09a80c9941de
+ build id event received for [vdso]: 8bbaf5dc62a9b644b4d4e4539737e104e4a84541
+ build id event received for /lib/x86_64-linux-gnu/libc-2.28.so: 5b157f49586a3ca84d55837f97ff466767dd3445
+ Samples for 'cycles' event do not have CPU attribute set. Skipping 'cpu' field.
+ Using CPUID GenuineIntel-6-8E-A
+ Using perf.data/kcore_dir/kcore for kernel data
+ Using perf.data/kcore_dir/kallsyms for symbols
+ perf 15316 2060795.480902: 1 cycles: ffffffffa2caa548 native_write_msr+0x8 (vmlinux)
+ perf 15316 2060795.480906: 1 cycles: ffffffffa2caa548 native_write_msr+0x8 (vmlinux)
+ perf 15316 2060795.480908: 7 cycles: ffffffffa2caa548 native_write_msr+0x8 (vmlinux)
+ perf 15316 2060795.480910: 119 cycles: ffffffffa2caa54a native_write_msr+0xa (vmlinux)
+ perf 15316 2060795.480912: 2109 cycles: ffffffffa2c9b7b0 native_apic_msr_write+0x0 (vmlinux)
+ perf 15316 2060795.480914: 37606 cycles: ffffffffa2f121fe perf_event_addr_filters_exec+0x2e (vmlinux)
+ uname 15316 2060795.480924: 588287 cycles: ffffffffa303a56d page_counter_try_charge+0x6d (vmlinux)
+ uname 15316 2060795.481067: 2261945 cycles: ffffffffa301438f kmem_cache_free+0x4f (vmlinux)
+ uname 15316 2060795.481643: 2172167 cycles: 7f1a48c393c0 _IO_un_link+0x0 (/lib/x86_64-linux-gnu/libc-2.28.so)