perf tools: Make perf.data more self-descriptive (v8)

The goal of this patch is to include more information about the host
environment into the perf.data so it is more self-descriptive. Overtime,
profiles are captured on various machines and it becomes hard to track
what was recorded, on what machine and when.

This patch provides a way to solve this by extending the perf.data file
with basic information about the host machine. To add those extensions,
we leverage the feature bits capabilities of the perf.data format.  The
change is backward compatible with existing perf.data files.

We define the following useful new extensions:
 - HEADER_HOSTNAME: the hostname
 - HEADER_OSRELEASE: the kernel release number
 - HEADER_ARCH: the hw architecture
 - HEADER_CPUDESC: generic CPU description
 - HEADER_NRCPUS: number of online/avail cpus
 - HEADER_CMDLINE: perf command line
 - HEADER_VERSION: perf version
 - HEADER_TOPOLOGY: cpu topology
 - HEADER_EVENT_DESC: full event description (attrs)
 - HEADER_CPUID: easy-to-parse low level CPU identication

The small granularity for the entries is to make it easier to extend
without breaking backward compatiblity. Many entries are provided as
ASCII strings.

Perf report/script have been modified to print the basic information as
easy-to-parse ASCII strings. Extended information about CPU and NUMA
topology may be requested with the -I option.

Thanks to David Ahern for reviewing and testing the many versions of
this patch.

 $ perf report --stdio
 # ========
 # captured on : Mon Sep 26 15:22:14 2011
 # hostname : quad
 # os release : 3.1.0-rc4-tip
 # perf version : 3.1.0-rc4
 # arch : x86_64
 # nrcpus online : 4
 # nrcpus avail : 4
 # cpudesc : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
 # cpuid : GenuineIntel,6,15,11
 # total memory : 8105360 kB
 # cmdline : /home/eranian/perfmon/official/tip/build/tools/perf/perf record date
 # event : name = cycles, type = 0, config = 0x0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, id = { 29, 30, 31,
 # HEADER_CPU_TOPOLOGY info available, use -I to display
 # HEADER_NUMA_TOPOLOGY info available, use -I to display
 # ========
 #
 ...

 $ perf report --stdio -I
 # ========
 # captured on : Mon Sep 26 15:22:14 2011
 # hostname : quad
 # os release : 3.1.0-rc4-tip
 # perf version : 3.1.0-rc4
 # arch : x86_64
 # nrcpus online : 4
 # nrcpus avail : 4
 # cpudesc : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
 # cpuid : GenuineIntel,6,15,11
 # total memory : 8105360 kB
 # cmdline : /home/eranian/perfmon/official/tip/build/tools/perf/perf record date
 # event : name = cycles, type = 0, config = 0x0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, id = { 29, 30, 31,
 # sibling cores   : 0-3
 # sibling threads : 0
 # sibling threads : 1
 # sibling threads : 2
 # sibling threads : 3
 # node0 meminfo  : total = 8320608 kB, free = 7571024 kB
 # node0 cpu list : 0-3
 # ========
 #
 ...

Reviewed-by: David Ahern <dsahern@gmail.com>
Tested-by: David Ahern <dsahern@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/20110930134040.GA5575@quad
Signed-off-by: Stephane Eranian <eranian@google.com>
[ committer notes: Use --show-info in the tools as was in the docs, rename
  perf_header_fprintf_info to perf_file_section__fprintf_info, fixup
  conflict with f69b64f7 "perf: Support setting the disassembler style" ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 1114 insertions, 31 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index b6c1ad123ca9..f2ceb0f7d669 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <linux/list.h>
 #include <linux/kernel.h>
+#include <sys/utsname.h>
 
 #include "evlist.h"
 #include "evsel.h"
@@ -17,12 +18,19 @@
 #include "session.h"
 #include "symbol.h"
 #include "debug.h"
+#include "cpumap.h"
 
 static bool no_buildid_cache = false;
 
 static int event_count;
 static struct perf_trace_event_type *events;
 
+static u32 header_argc;
+static const char **header_argv;
+
+static int dsos__write_buildid_table(struct perf_header *header, int fd);
+static int perf_session__cache_build_ids(struct perf_session *session);
+
 int perf_header__push_event(u64 id, const char *name)
 {
 	if (strlen(name) > MAX_EVENT_NAME)
@@ -110,6 +118,1020 @@ static int write_padded(int fd, const void *bf, size_t count,
 	return err;
 }
 
+static int do_write_string(int fd, const char *str)
+{
+	u32 len, olen;
+	int ret;
+
+	olen = strlen(str) + 1;
+	len = ALIGN(olen, NAME_ALIGN);
+
+	/* write len, incl. \0 */
+	ret = do_write(fd, &len, sizeof(len));
+	if (ret < 0)
+		return ret;
+
+	return write_padded(fd, str, olen, len);
+}
+
+static char *do_read_string(int fd, struct perf_header *ph)
+{
+	ssize_t sz, ret;
+	u32 len;
+	char *buf;
+
+	sz = read(fd, &len, sizeof(len));
+	if (sz < (ssize_t)sizeof(len))
+		return NULL;
+
+	if (ph->needs_swap)
+		len = bswap_32(len);
+
+	buf = malloc(len);
+	if (!buf)
+		return NULL;
+
+	ret = read(fd, buf, len);
+	if (ret == (ssize_t)len) {
+		/*
+		 * strings are padded by zeroes
+		 * thus the actual strlen of buf
+		 * may be less than len
+		 */
+		return buf;
+	}
+
+	free(buf);
+	return NULL;
+}
+
+int
+perf_header__set_cmdline(int argc, const char **argv)
+{
+	int i;
+
+	header_argc = (u32)argc;
+
+	/* do not include NULL termination */
+	header_argv = calloc(argc, sizeof(char *));
+	if (!header_argv)
+		return -ENOMEM;
+
+	/*
+	 * must copy argv contents because it gets moved
+	 * around during option parsing
+	 */
+	for (i = 0; i < argc ; i++)
+		header_argv[i] = argv[i];
+
+	return 0;
+}
+
+static int write_trace_info(int fd, struct perf_header *h __used,
+			    struct perf_evlist *evlist)
+{
+	return read_tracing_data(fd, &evlist->entries);
+}
+
+
+static int write_build_id(int fd, struct perf_header *h,
+			  struct perf_evlist *evlist __used)
+{
+	struct perf_session *session;
+	int err;
+
+	session = container_of(h, struct perf_session, header);
+
+	err = dsos__write_buildid_table(h, fd);
+	if (err < 0) {
+		pr_debug("failed to write buildid table\n");
+		return err;
+	}
+	if (!no_buildid_cache)
+		perf_session__cache_build_ids(session);
+
+	return 0;
+}
+
+static int write_hostname(int fd, struct perf_header *h __used,
+			  struct perf_evlist *evlist __used)
+{
+	struct utsname uts;
+	int ret;
+
+	ret = uname(&uts);
+	if (ret < 0)
+		return -1;
+
+	return do_write_string(fd, uts.nodename);
+}
+
+static int write_osrelease(int fd, struct perf_header *h __used,
+			   struct perf_evlist *evlist __used)
+{
+	struct utsname uts;
+	int ret;
+
+	ret = uname(&uts);
+	if (ret < 0)
+		return -1;
+
+	return do_write_string(fd, uts.release);
+}
+
+static int write_arch(int fd, struct perf_header *h __used,
+		      struct perf_evlist *evlist __used)
+{
+	struct utsname uts;
+	int ret;
+
+	ret = uname(&uts);
+	if (ret < 0)
+		return -1;
+
+	return do_write_string(fd, uts.machine);
+}
+
+static int write_version(int fd, struct perf_header *h __used,
+			 struct perf_evlist *evlist __used)
+{
+	return do_write_string(fd, perf_version_string);
+}
+
+static int write_cpudesc(int fd, struct perf_header *h __used,
+		       struct perf_evlist *evlist __used)
+{
+#ifndef CPUINFO_PROC
+#define CPUINFO_PROC NULL
+#endif
+	FILE *file;
+	char *buf = NULL;
+	char *s, *p;
+	const char *search = CPUINFO_PROC;
+	size_t len = 0;
+	int ret = -1;
+
+	if (!search)
+		return -1;
+
+	file = fopen("/proc/cpuinfo", "r");
+	if (!file)
+		return -1;
+
+	while (getline(&buf, &len, file) > 0) {
+		ret = strncmp(buf, search, strlen(search));
+		if (!ret)
+			break;
+	}
+
+	if (ret)
+		goto done;
+
+	s = buf;
+
+	p = strchr(buf, ':');
+	if (p && *(p+1) == ' ' && *(p+2))
+		s = p + 2;
+	p = strchr(s, '\n');
+	if (p)
+		*p = '\0';
+
+	/* squash extra space characters (branding string) */
+	p = s;
+	while (*p) {
+		if (isspace(*p)) {
+			char *r = p + 1;
+			char *q = r;
+			*p = ' ';
+			while (*q && isspace(*q))
+				q++;
+			if (q != (p+1))
+				while ((*r++ = *q++));
+		}
+		p++;
+	}
+	ret = do_write_string(fd, s);
+done:
+	free(buf);
+	fclose(file);
+	return ret;
+}
+
+static int write_nrcpus(int fd, struct perf_header *h __used,
+			struct perf_evlist *evlist __used)
+{
+	long nr;
+	u32 nrc, nra;
+	int ret;
+
+	nr = sysconf(_SC_NPROCESSORS_CONF);
+	if (nr < 0)
+		return -1;
+
+	nrc = (u32)(nr & UINT_MAX);
+
+	nr = sysconf(_SC_NPROCESSORS_ONLN);
+	if (nr < 0)
+		return -1;
+
+	nra = (u32)(nr & UINT_MAX);
+
+	ret = do_write(fd, &nrc, sizeof(nrc));
+	if (ret < 0)
+		return ret;
+
+	return do_write(fd, &nra, sizeof(nra));
+}
+
+static int write_event_desc(int fd, struct perf_header *h __used,
+			    struct perf_evlist *evlist)
+{
+	struct perf_evsel *attr;
+	u32 nre = 0, nri, sz;
+	int ret;
+
+	list_for_each_entry(attr, &evlist->entries, node)
+		nre++;
+
+	/*
+	 * write number of events
+	 */
+	ret = do_write(fd, &nre, sizeof(nre));
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * size of perf_event_attr struct
+	 */
+	sz = (u32)sizeof(attr->attr);
+	ret = do_write(fd, &sz, sizeof(sz));
+	if (ret < 0)
+		return ret;
+
+	list_for_each_entry(attr, &evlist->entries, node) {
+
+		ret = do_write(fd, &attr->attr, sz);
+		if (ret < 0)
+			return ret;
+		/*
+		 * write number of unique id per event
+		 * there is one id per instance of an event
+		 *
+		 * copy into an nri to be independent of the
+		 * type of ids,
+		 */
+		nri = attr->ids;
+		ret = do_write(fd, &nri, sizeof(nri));
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * write event string as passed on cmdline
+		 */
+		ret = do_write_string(fd, attr->name);
+		if (ret < 0)
+			return ret;
+		/*
+		 * write unique ids for this event
+		 */
+		ret = do_write(fd, attr->id, attr->ids * sizeof(u64));
+		if (ret < 0)
+			return ret;
+	}
+	return 0;
+}
+
+static int write_cmdline(int fd, struct perf_header *h __used,
+			 struct perf_evlist *evlist __used)
+{
+	char buf[MAXPATHLEN];
+	char proc[32];
+	u32 i, n;
+	int ret;
+
+	/*
+	 * actual atual path to perf binary
+	 */
+	sprintf(proc, "/proc/%d/exe", getpid());
+	ret = readlink(proc, buf, sizeof(buf));
+	if (ret <= 0)
+		return -1;
+
+	/* readlink() does not add null termination */
+	buf[ret] = '\0';
+
+	/* account for binary path */
+	n = header_argc + 1;
+
+	ret = do_write(fd, &n, sizeof(n));
+	if (ret < 0)
+		return ret;
+
+	ret = do_write_string(fd, buf);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0 ; i < header_argc; i++) {
+		ret = do_write_string(fd, header_argv[i]);
+		if (ret < 0)
+			return ret;
+	}
+	return 0;
+}
+
+#define CORE_SIB_FMT \
+	"/sys/devices/system/cpu/cpu%d/topology/core_siblings_list"
+#define THRD_SIB_FMT \
+	"/sys/devices/system/cpu/cpu%d/topology/thread_siblings_list"
+
+struct cpu_topo {
+	u32 core_sib;
+	u32 thread_sib;
+	char **core_siblings;
+	char **thread_siblings;
+};
+
+static int build_cpu_topo(struct cpu_topo *tp, int cpu)
+{
+	FILE *fp;
+	char filename[MAXPATHLEN];
+	char *buf = NULL, *p;
+	size_t len = 0;
+	u32 i = 0;
+	int ret = -1;
+
+	sprintf(filename, CORE_SIB_FMT, cpu);
+	fp = fopen(filename, "r");
+	if (!fp)
+		return -1;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto done;
+
+	fclose(fp);
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	for (i = 0; i < tp->core_sib; i++) {
+		if (!strcmp(buf, tp->core_siblings[i]))
+			break;
+	}
+	if (i == tp->core_sib) {
+		tp->core_siblings[i] = buf;
+		tp->core_sib++;
+		buf = NULL;
+		len = 0;
+	}
+
+	sprintf(filename, THRD_SIB_FMT, cpu);
+	fp = fopen(filename, "r");
+	if (!fp)
+		goto done;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto done;
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	for (i = 0; i < tp->thread_sib; i++) {
+		if (!strcmp(buf, tp->thread_siblings[i]))
+			break;
+	}
+	if (i == tp->thread_sib) {
+		tp->thread_siblings[i] = buf;
+		tp->thread_sib++;
+		buf = NULL;
+	}
+	ret = 0;
+done:
+	if(fp)
+		fclose(fp);
+	free(buf);
+	return ret;
+}
+
+static void free_cpu_topo(struct cpu_topo *tp)
+{
+	u32 i;
+
+	if (!tp)
+		return;
+
+	for (i = 0 ; i < tp->core_sib; i++)
+		free(tp->core_siblings[i]);
+
+	for (i = 0 ; i < tp->thread_sib; i++)
+		free(tp->thread_siblings[i]);
+
+	free(tp);
+}
+
+static struct cpu_topo *build_cpu_topology(void)
+{
+	struct cpu_topo *tp;
+	void *addr;
+	u32 nr, i;
+	size_t sz;
+	long ncpus;
+	int ret = -1;
+
+	ncpus = sysconf(_SC_NPROCESSORS_CONF);
+	if (ncpus < 0)
+		return NULL;
+
+	nr = (u32)(ncpus & UINT_MAX);
+
+	sz = nr * sizeof(char *);
+
+	addr = calloc(1, sizeof(*tp) + 2 * sz);
+	if (!addr)
+		return NULL;
+
+	tp = addr;
+
+	addr += sizeof(*tp);
+	tp->core_siblings = addr;
+	addr += sz;
+	tp->thread_siblings = addr;
+
+	for (i = 0; i < nr; i++) {
+		ret = build_cpu_topo(tp, i);
+		if (ret < 0)
+			break;
+	}
+	if (ret) {
+		free_cpu_topo(tp);
+		tp = NULL;
+	}
+	return tp;
+}
+
+static int write_cpu_topology(int fd, struct perf_header *h __used,
+			  struct perf_evlist *evlist __used)
+{
+	struct cpu_topo *tp;
+	u32 i;
+	int ret;
+
+	tp = build_cpu_topology();
+	if (!tp)
+		return -1;
+
+	ret = do_write(fd, &tp->core_sib, sizeof(tp->core_sib));
+	if (ret < 0)
+		goto done;
+
+	for (i = 0; i < tp->core_sib; i++) {
+		ret = do_write_string(fd, tp->core_siblings[i]);
+		if (ret < 0)
+			goto done;
+	}
+	ret = do_write(fd, &tp->thread_sib, sizeof(tp->thread_sib));
+	if (ret < 0)
+		goto done;
+
+	for (i = 0; i < tp->thread_sib; i++) {
+		ret = do_write_string(fd, tp->thread_siblings[i]);
+		if (ret < 0)
+			break;
+	}
+done:
+	free_cpu_topo(tp);
+	return ret;
+}
+
+
+
+static int write_total_mem(int fd, struct perf_header *h __used,
+			  struct perf_evlist *evlist __used)
+{
+	char *buf = NULL;
+	FILE *fp;
+	size_t len = 0;
+	int ret = -1, n;
+	uint64_t mem;
+
+	fp = fopen("/proc/meminfo", "r");
+	if (!fp)
+		return -1;
+
+	while (getline(&buf, &len, fp) > 0) {
+		ret = strncmp(buf, "MemTotal:", 9);
+		if (!ret)
+			break;
+	}
+	if (!ret) {
+		n = sscanf(buf, "%*s %"PRIu64, &mem);
+		if (n == 1)
+			ret = do_write(fd, &mem, sizeof(mem));
+	}
+	free(buf);
+	fclose(fp);
+	return ret;
+}
+
+static int write_topo_node(int fd, int node)
+{
+	char str[MAXPATHLEN];
+	char field[32];
+	char *buf = NULL, *p;
+	size_t len = 0;
+	FILE *fp;
+	u64 mem_total, mem_free, mem;
+	int ret = -1;
+
+	sprintf(str, "/sys/devices/system/node/node%d/meminfo", node);
+	fp = fopen(str, "r");
+	if (!fp)
+		return -1;
+
+	while (getline(&buf, &len, fp) > 0) {
+		/* skip over invalid lines */
+		if (!strchr(buf, ':'))
+			continue;
+		if (sscanf(buf, "%*s %*d %s %"PRIu64, field, &mem) != 2)
+			goto done;
+		if (!strcmp(field, "MemTotal:"))
+			mem_total = mem;
+		if (!strcmp(field, "MemFree:"))
+			mem_free = mem;
+	}
+
+	fclose(fp);
+
+	ret = do_write(fd, &mem_total, sizeof(u64));
+	if (ret)
+		goto done;
+
+	ret = do_write(fd, &mem_free, sizeof(u64));
+	if (ret)
+		goto done;
+
+	ret = -1;
+	sprintf(str, "/sys/devices/system/node/node%d/cpulist", node);
+
+	fp = fopen(str, "r");
+	if (!fp)
+		goto done;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto done;
+
+	p = strchr(buf, '\n');
+	if (p)
+		*p = '\0';
+
+	ret = do_write_string(fd, buf);
+done:
+	free(buf);
+	fclose(fp);
+	return ret;
+}
+
+static int write_numa_topology(int fd, struct perf_header *h __used,
+			  struct perf_evlist *evlist __used)
+{
+	char *buf = NULL;
+	size_t len = 0;
+	FILE *fp;
+	struct cpu_map *node_map = NULL;
+	char *c;
+	u32 nr, i, j;
+	int ret = -1;
+
+	fp = fopen("/sys/devices/system/node/online", "r");
+	if (!fp)
+		return -1;
+
+	if (getline(&buf, &len, fp) <= 0)
+		goto done;
+
+	c = strchr(buf, '\n');
+	if (c)
+		*c = '\0';
+
+	node_map = cpu_map__new(buf);
+	if (!node_map)
+		goto done;
+
+	nr = (u32)node_map->nr;
+
+	ret = do_write(fd, &nr, sizeof(nr));
+	if (ret < 0)
+		goto done;
+
+	for (i = 0; i < nr; i++) {
+		j = (u32)node_map->map[i];
+		ret = do_write(fd, &j, sizeof(j));
+		if (ret < 0)
+			break;
+
+		ret = write_topo_node(fd, i);
+		if (ret < 0)
+			break;
+	}
+done:
+	free(buf);
+	fclose(fp);
+	free(node_map);
+	return ret;
+}
+
+/*
+ * default get_cpuid(): nothing gets recorded
+ * actual implementation must be in arch/$(ARCH)/util/header.c
+ */
+int __attribute__((weak)) get_cpuid(char *buffer __used, size_t sz __used)
+{
+	return -1;
+}
+
+static int write_cpuid(int fd, struct perf_header *h __used,
+		       struct perf_evlist *evlist __used)
+{
+	char buffer[64];
+	int ret;
+
+	ret = get_cpuid(buffer, sizeof(buffer));
+	if (!ret)
+		goto write_it;
+
+	return -1;
+write_it:
+	return do_write_string(fd, buffer);
+}
+
+static void print_hostname(struct perf_header *ph, int fd, FILE *fp)
+{
+	char *str = do_read_string(fd, ph);
+	fprintf(fp, "# hostname : %s\n", str);
+	free(str);
+}
+
+static void print_osrelease(struct perf_header *ph, int fd, FILE *fp)
+{
+	char *str = do_read_string(fd, ph);
+	fprintf(fp, "# os release : %s\n", str);
+	free(str);
+}
+
+static void print_arch(struct perf_header *ph, int fd, FILE *fp)
+{
+	char *str = do_read_string(fd, ph);
+	fprintf(fp, "# arch : %s\n", str);
+	free(str);
+}
+
+static void print_cpudesc(struct perf_header *ph, int fd, FILE *fp)
+{
+	char *str = do_read_string(fd, ph);
+	fprintf(fp, "# cpudesc : %s\n", str);
+	free(str);
+}
+
+static void print_nrcpus(struct perf_header *ph, int fd, FILE *fp)
+{
+	ssize_t ret;
+	u32 nr;
+
+	ret = read(fd, &nr, sizeof(nr));
+	if (ret != (ssize_t)sizeof(nr))
+		nr = -1; /* interpreted as error */
+
+	if (ph->needs_swap)
+		nr = bswap_32(nr);
+
+	fprintf(fp, "# nrcpus online : %u\n", nr);
+
+	ret = read(fd, &nr, sizeof(nr));
+	if (ret != (ssize_t)sizeof(nr))
+		nr = -1; /* interpreted as error */
+
+	if (ph->needs_swap)
+		nr = bswap_32(nr);
+
+	fprintf(fp, "# nrcpus avail : %u\n", nr);
+}
+
+static void print_version(struct perf_header *ph, int fd, FILE *fp)
+{
+	char *str = do_read_string(fd, ph);
+	fprintf(fp, "# perf version : %s\n", str);
+	free(str);
+}
+
+static void print_cmdline(struct perf_header *ph, int fd, FILE *fp)
+{
+	ssize_t ret;
+	char *str;
+	u32 nr, i;
+
+	ret = read(fd, &nr, sizeof(nr));
+	if (ret != (ssize_t)sizeof(nr))
+		return;
+
+	if (ph->needs_swap)
+		nr = bswap_32(nr);
+
+	fprintf(fp, "# cmdline : ");
+
+	for (i = 0; i < nr; i++) {
+		str = do_read_string(fd, ph);
+		fprintf(fp, "%s ", str);
+		free(str);
+	}
+	fputc('\n', fp);
+}
+
+static void print_cpu_topology(struct perf_header *ph, int fd, FILE *fp)
+{
+	ssize_t ret;
+	u32 nr, i;
+	char *str;
+
+	ret = read(fd, &nr, sizeof(nr));
+	if (ret != (ssize_t)sizeof(nr))
+		return;
+
+	if (ph->needs_swap)
+		nr = bswap_32(nr);
+
+	for (i = 0; i < nr; i++) {
+		str = do_read_string(fd, ph);
+		fprintf(fp, "# sibling cores   : %s\n", str);
+		free(str);
+	}
+
+	ret = read(fd, &nr, sizeof(nr));
+	if (ret != (ssize_t)sizeof(nr))
+		return;
+
+	if (ph->needs_swap)
+		nr = bswap_32(nr);
+
+	for (i = 0; i < nr; i++) {
+		str = do_read_string(fd, ph);
+		fprintf(fp, "# sibling threads : %s\n", str);
+		free(str);
+	}
+}
+
+static void print_event_desc(struct perf_header *ph, int fd, FILE *fp)
+{
+	struct perf_event_attr attr;
+	uint64_t id;
+	void *buf = NULL;
+	char *str;
+	u32 nre, sz, nr, i, j, msz;
+	int ret;
+
+	/* number of events */
+	ret = read(fd, &nre, sizeof(nre));
+	if (ret != (ssize_t)sizeof(nre))
+		goto error;
+
+	if (ph->needs_swap)
+		nre = bswap_32(nre);
+
+	ret = read(fd, &sz, sizeof(sz));
+	if (ret != (ssize_t)sizeof(sz))
+		goto error;
+
+	if (ph->needs_swap)
+		sz = bswap_32(sz);
+
+	/*
+	 * ensure it is at least to our ABI rev
+	 */
+	if (sz < (u32)sizeof(attr))
+		goto error;
+
+	memset(&attr, 0, sizeof(attr));
+
+	/* read entire region to sync up to next field */
+	buf = malloc(sz);
+	if (!buf)
+		goto error;
+
+	msz = sizeof(attr);
+	if (sz < msz)
+		msz = sz;
+
+	for (i = 0 ; i < nre; i++) {
+
+		ret = read(fd, buf, sz);
+		if (ret != (ssize_t)sz)
+			goto error;
+
+		if (ph->needs_swap)
+			perf_event__attr_swap(buf);
+
+		memcpy(&attr, buf, msz);
+
+		ret = read(fd, &nr, sizeof(nr));
+		if (ret != (ssize_t)sizeof(nr))
+			goto error;
+
+		if (ph->needs_swap)
+			nr = bswap_32(nr);
+
+		str = do_read_string(fd, ph);
+		fprintf(fp, "# event : name = %s, ", str);
+		free(str);
+
+		fprintf(fp, "type = %d, config = 0x%"PRIx64
+			    ", config1 = 0x%"PRIx64", config2 = 0x%"PRIx64,
+				attr.type,
+				(u64)attr.config,
+				(u64)attr.config1,
+				(u64)attr.config2);
+
+		fprintf(fp, ", excl_usr = %d, excl_kern = %d",
+				attr.exclude_user,
+				attr.exclude_kernel);
+
+		if (nr)
+			fprintf(fp, ", id = {");
+
+		for (j = 0 ; j < nr; j++) {
+			ret = read(fd, &id, sizeof(id));
+			if (ret != (ssize_t)sizeof(id))
+				goto error;
+
+			if (ph->needs_swap)
+				id = bswap_64(id);
+
+			if (j)
+				fputc(',', fp);
+
+			fprintf(fp, " %"PRIu64, id);
+		}
+		if (nr && j == nr)
+			fprintf(fp, " }");
+		fputc('\n', fp);
+	}
+	free(buf);
+	return;
+error:
+	fprintf(fp, "# event desc: not available or unable to read\n");
+}
+
+static void print_total_mem(struct perf_header *h __used, int fd, FILE *fp)
+{
+	uint64_t mem;
+	ssize_t ret;
+
+	ret = read(fd, &mem, sizeof(mem));
+	if (ret != sizeof(mem))
+		goto error;
+
+	if (h->needs_swap)
+		mem = bswap_64(mem);
+
+	fprintf(fp, "# total memory : %"PRIu64" kB\n", mem);
+	return;
+error:
+	fprintf(fp, "# total memory : unknown\n");
+}
+
+static void print_numa_topology(struct perf_header *h __used, int fd, FILE *fp)
+{
+	ssize_t ret;
+	u32 nr, c, i;
+	char *str;
+	uint64_t mem_total, mem_free;
+
+	/* nr nodes */
+	ret = read(fd, &nr, sizeof(nr));
+	if (ret != (ssize_t)sizeof(nr))
+		goto error;
+
+	if (h->needs_swap)
+		nr = bswap_32(nr);
+
+	for (i = 0; i < nr; i++) {
+
+		/* node number */
+		ret = read(fd, &c, sizeof(c));
+		if (ret != (ssize_t)sizeof(c))
+			goto error;
+
+		if (h->needs_swap)
+			c = bswap_32(c);
+
+		ret = read(fd, &mem_total, sizeof(u64));
+		if (ret != sizeof(u64))
+			goto error;
+
+		ret = read(fd, &mem_free, sizeof(u64));
+		if (ret != sizeof(u64))
+			goto error;
+
+		if (h->needs_swap) {
+			mem_total = bswap_64(mem_total);
+			mem_free = bswap_64(mem_free);
+		}
+
+		fprintf(fp, "# node%u meminfo  : total = %"PRIu64" kB,"
+			    " free = %"PRIu64" kB\n",
+			c,
+			mem_total,
+			mem_free);
+
+		str = do_read_string(fd, h);
+		fprintf(fp, "# node%u cpu list : %s\n", c, str);
+		free(str);
+	}
+	return;
+error:
+	fprintf(fp, "# numa topology : not available\n");
+}
+
+static void print_cpuid(struct perf_header *ph, int fd, FILE *fp)
+{
+	char *str = do_read_string(fd, ph);
+	fprintf(fp, "# cpuid : %s\n", str);
+	free(str);
+}
+
+struct feature_ops {
+	int (*write)(int fd, struct perf_header *h, struct perf_evlist *evlist);
+	void (*print)(struct perf_header *h, int fd, FILE *fp);
+	const char *name;
+	bool full_only;
+};
+
+#define FEAT_OPA(n, w, p) \
+	[n] = { .name = #n, .write = w, .print = p }
+#define FEAT_OPF(n, w, p) \
+	[n] = { .name = #n, .write = w, .print = p, .full_only = true }
+
+static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
+	FEAT_OPA(HEADER_TRACE_INFO, write_trace_info, NULL),
+	FEAT_OPA(HEADER_BUILD_ID, write_build_id, NULL),
+	FEAT_OPA(HEADER_HOSTNAME, write_hostname, print_hostname),
+	FEAT_OPA(HEADER_OSRELEASE, write_osrelease, print_osrelease),
+	FEAT_OPA(HEADER_VERSION, write_version, print_version),
+	FEAT_OPA(HEADER_ARCH, write_arch, print_arch),
+	FEAT_OPA(HEADER_NRCPUS, write_nrcpus, print_nrcpus),
+	FEAT_OPA(HEADER_CPUDESC, write_cpudesc, print_cpudesc),
+	FEAT_OPA(HEADER_CPUID, write_cpuid, print_cpuid),
+	FEAT_OPA(HEADER_TOTAL_MEM, write_total_mem, print_total_mem),
+	FEAT_OPA(HEADER_EVENT_DESC, write_event_desc, print_event_desc),
+	FEAT_OPA(HEADER_CMDLINE, write_cmdline, print_cmdline),
+	FEAT_OPF(HEADER_CPU_TOPOLOGY, write_cpu_topology, print_cpu_topology),
+	FEAT_OPF(HEADER_NUMA_TOPOLOGY, write_numa_topology, print_numa_topology),
+};
+
+struct header_print_data {
+	FILE *fp;
+	bool full; /* extended list of headers */
+};
+
+static int perf_file_section__fprintf_info(struct perf_file_section *section,
+					   struct perf_header *ph,
+					   int feat, int fd, void *data)
+{
+	struct header_print_data *hd = data;
+
+	if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
+		pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
+				"%d, continuing...\n", section->offset, feat);
+		return 0;
+	}
+	if (feat < HEADER_TRACE_INFO || feat >= HEADER_LAST_FEATURE) {
+		pr_warning("unknown feature %d\n", feat);
+		return -1;
+	}
+	if (!feat_ops[feat].print)
+		return 0;
+
+	if (!feat_ops[feat].full_only || hd->full)
+		feat_ops[feat].print(ph, fd, hd->fp);
+	else
+		fprintf(hd->fp, "# %s info available, use -I to display\n",
+			feat_ops[feat].name);
+
+	return 0;
+}
+
+int perf_header__fprintf_info(struct perf_session *session, FILE *fp, bool full)
+{
+	struct header_print_data hd;
+	struct perf_header *header = &session->header;
+	int fd = session->fd;
+	hd.fp = fp;
+	hd.full = full;
+
+	perf_header__process_sections(header, fd, &hd,
+				      perf_file_section__fprintf_info);
+	return 0;
+}
+
 #define dsos__for_each_with_build_id(pos, head)	\
 	list_for_each_entry(pos, head, node)	\
 		if (!pos->has_build_id)		\
@@ -356,15 +1378,41 @@ static bool perf_session__read_build_ids(struct perf_session *session, bool with
 	return ret;
 }
 
+static int do_write_feat(int fd, struct perf_header *h, int type,
+			 struct perf_file_section **p,
+			 struct perf_evlist *evlist)
+{
+	int err;
+	int ret = 0;
+
+	if (perf_header__has_feat(h, type)) {
+
+		(*p)->offset = lseek(fd, 0, SEEK_CUR);
+
+		err = feat_ops[type].write(fd, h, evlist);
+		if (err < 0) {
+			pr_debug("failed to write feature %d\n", type);
+
+			/* undo anything written */
+			lseek(fd, (*p)->offset, SEEK_SET);
+
+			return -1;
+		}
+		(*p)->size = lseek(fd, 0, SEEK_CUR) - (*p)->offset;
+		(*p)++;
+	}
+	return ret;
+}
+
 static int perf_header__adds_write(struct perf_header *header,
 				   struct perf_evlist *evlist, int fd)
 {
 	int nr_sections;
 	struct perf_session *session;
-	struct perf_file_section *feat_sec;
+	struct perf_file_section *feat_sec, *p;
 	int sec_size;
 	u64 sec_start;
-	int idx = 0, err;
+	int err;
 
 	session = container_of(header, struct perf_session, header);
 
@@ -376,7 +1424,7 @@ static int perf_header__adds_write(struct perf_header *header,
 	if (!nr_sections)
 		return 0;
 
-	feat_sec = calloc(sizeof(*feat_sec), nr_sections);
+	feat_sec = p = calloc(sizeof(*feat_sec), nr_sections);
 	if (feat_sec == NULL)
 		return -ENOMEM;
 
@@ -385,36 +1433,69 @@ static int perf_header__adds_write(struct perf_header *header,
 	sec_start = header->data_offset + header->data_size;
 	lseek(fd, sec_start + sec_size, SEEK_SET);
 
-	if (perf_header__has_feat(header, HEADER_TRACE_INFO)) {
-		struct perf_file_section *trace_sec;
-
-		trace_sec = &feat_sec[idx++];
+	err = do_write_feat(fd, header, HEADER_TRACE_INFO, &p, evlist);
+	if (err)
+		goto out_free;
 
-		/* Write trace info */
-		trace_sec->offset = lseek(fd, 0, SEEK_CUR);
-		read_tracing_data(fd, &evlist->entries);
-		trace_sec->size = lseek(fd, 0, SEEK_CUR) - trace_sec->offset;
+	err = do_write_feat(fd, header, HEADER_BUILD_ID, &p, evlist);
+	if (err) {
+		perf_header__clear_feat(header, HEADER_BUILD_ID);
+		goto out_free;
 	}
 
-	if (perf_header__has_feat(header, HEADER_BUILD_ID)) {
-		struct perf_file_section *buildid_sec;
+	err = do_write_feat(fd, header, HEADER_HOSTNAME, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_HOSTNAME);
 
-		buildid_sec = &feat_sec[idx++];
+	err = do_write_feat(fd, header, HEADER_OSRELEASE, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_OSRELEASE);
 
-		/* Write build-ids */
-		buildid_sec->offset = lseek(fd, 0, SEEK_CUR);
-		err = dsos__write_buildid_table(header, fd);
-		if (err < 0) {
-			pr_debug("failed to write buildid table\n");
-			goto out_free;
-		}
-		buildid_sec->size = lseek(fd, 0, SEEK_CUR) -
-					  buildid_sec->offset;
-		if (!no_buildid_cache)
-			perf_session__cache_build_ids(session);
-	}
+	err = do_write_feat(fd, header, HEADER_VERSION, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_VERSION);
+
+	err = do_write_feat(fd, header, HEADER_ARCH, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_ARCH);
+
+	err = do_write_feat(fd, header, HEADER_NRCPUS, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_NRCPUS);
+
+	err = do_write_feat(fd, header, HEADER_CPUDESC, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_CPUDESC);
+
+	err = do_write_feat(fd, header, HEADER_CPUID, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_CPUID);
+
+	err = do_write_feat(fd, header, HEADER_TOTAL_MEM, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_TOTAL_MEM);
+
+	err = do_write_feat(fd, header, HEADER_CMDLINE, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_CMDLINE);
+
+	err = do_write_feat(fd, header, HEADER_EVENT_DESC, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_EVENT_DESC);
+
+	err = do_write_feat(fd, header, HEADER_CPU_TOPOLOGY, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_CPU_TOPOLOGY);
+
+	err = do_write_feat(fd, header, HEADER_NUMA_TOPOLOGY, &p, evlist);
+	if (err)
+		perf_header__clear_feat(header, HEADER_NUMA_TOPOLOGY);
 
 	lseek(fd, sec_start, SEEK_SET);
+	/*
+	 * may write more than needed due to dropped feature, but
+	 * this is okay, reader will skip the mising entries
+	 */
 	err = do_write(fd, feat_sec, sec_size);
 	if (err < 0)
 		pr_debug("failed to write feature section\n");
@@ -554,9 +1635,10 @@ static int perf_header__getbuffer64(struct perf_header *header,
 }
 
 int perf_header__process_sections(struct perf_header *header, int fd,
+				  void *data,
 				  int (*process)(struct perf_file_section *section,
-						 struct perf_header *ph,
-						 int feat, int fd))
+				  struct perf_header *ph,
+				  int feat, int fd, void *data))
 {
 	struct perf_file_section *feat_sec;
 	int nr_sections;
@@ -584,7 +1666,7 @@ int perf_header__process_sections(struct perf_header *header, int fd,
 		if (perf_header__has_feat(header, feat)) {
 			struct perf_file_section *sec = &feat_sec[idx++];
 
-			err = process(sec, header, feat, fd);
+			err = process(sec, header, feat, fd, data);
 			if (err < 0)
 				break;
 		}
@@ -796,7 +1878,7 @@ out:
 
 static int perf_file_section__process(struct perf_file_section *section,
 				      struct perf_header *ph,
-				      int feat, int fd)
+				      int feat, int fd, void *data __used)
 {
 	if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
 		pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
@@ -935,7 +2017,8 @@ int perf_session__read_header(struct perf_session *session, int fd)
 		event_count =  f_header.event_types.size / sizeof(struct perf_trace_event_type);
 	}
 
-	perf_header__process_sections(header, fd, perf_file_section__process);
+	perf_header__process_sections(header, fd, NULL,
+				      perf_file_section__process);
 
 	lseek(fd, header->data_offset, SEEK_SET);