perf/cover improvements and fixes

Hi Ingo,

Please consider pulling,

- Arnaldo

The following changes since commit c2365b9388e8ec19305e3f449c1826e7493d156d:

perf/x86/intel/uncore: Do not use macro DEFINE_PCI_DEVICE_TABLE() (2015-10-01 10:53:03 +0200)

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tags/perf-core-for-mingo

for you to fetch changes up to 19afd10410957b1c808c2c49a88e6dd8b23aa894:

  perf stat: Reduce min --interval-print to 10ms (2015-10-02 17:07:55 -0300)

----------------------------------------------------------------
perf/core improvements and fixes:

User visible:

- Do event name substring search as last resort in 'perf list'. (Arnaldo Carvalho de Melo)

E.g.:

   # perf list clock

List of pre-defined events (to be used in -e):

cpu-clock [Software event]
task-clock [Software event]

uncore_cbox_0/clockticks/ [Kernel PMU event]
uncore_cbox_1/clockticks/ [Kernel PMU event]

kvm:kvm_pvclock_update [Tracepoint event]
kvm:kvm_update_master_clock [Tracepoint event]
power:clock_disable [Tracepoint event]
power:clock_enable [Tracepoint event]
power:clock_set_rate [Tracepoint event]
syscalls:sys_enter_clock_adjtime [Tracepoint event]
syscalls:sys_enter_clock_getres [Tracepoint event]
syscalls:sys_enter_clock_gettime [Tracepoint event]
syscalls:sys_enter_clock_nanosleep [Tracepoint event]
syscalls:sys_enter_clock_settime [Tracepoint event]
syscalls:sys_exit_clock_adjtime [Tracepoint event]
syscalls:sys_exit_clock_getres [Tracepoint event]
syscalls:sys_exit_clock_gettime [Tracepoint event]
syscalls:sys_exit_clock_nanosleep [Tracepoint event]
syscalls:sys_exit_clock_settime [Tracepoint event]

- Reduce min 'perf stat --interval-print/-I' to 10ms (Kan Liang)

perf stat --interval in action:

  # perf stat -e cycles -I 50 -a usleep $((200 * 1000))
  print interval < 100ms. The overhead percentage could be high in some cases. Please proceed with caution.
  #   time                    counts unit events
      0.050233636         48,240,396      cycles
      0.100557098         35,492,594      cycles
      0.150804687         39,295,112      cycles
      0.201032269         33,101,961      cycles
      0.201980732            786,379      cycles
  #

- Allow for max_stack greater than PERF_MAX_STACK_DEPTH, as when synthesizing callchains from Intel PT data (Adrian Hunter)

- Allow probing on kmodules without DWARF (Masami Hiramatsu)

- Fix a segfault when processing a perf.data file with callchains using "perf report --call-graph none" (Namhyung Kim)

- Fix unresolved COMMs in 'perf top' when -s comm is used (Namhyung Kim)

- Register idle thread in 'perf top' (Namhyung Kim)

- Change 'record.samples' type to unsigned long long, fixing output of number of samples in 32-bit architectures (Yang Shi)

----------------------------------------------------------------
Adrian Hunter (1):
perf callchain: Allow for max_stack greater than PERF_MAX_STACK_DEPTH

Arnaldo Carvalho de Melo (2):
perf list: Do event name substring search as last resort when no events found perf list: Honour 'event_glob' whem printing selectable PMUs

Kan Liang (1):
perf stat: Reduce min --interval-print to 10ms

Masami Hiramatsu (1):
perf probe: Allow probing on kmodules without dwarf

Namhyung Kim (4):
perf record: Allocate area for sample_id_hdr in a synthesized comm event perf top: Fix unresolved comm when -s comm is used
perf top: Register idle thread
perf report: Fix a bug on "--call-graph none" option

Yang Shi (1):
perf record: Change 'record.samples' type to unsigned long long

 tools/perf/Documentation/perf-list.txt |  2 ++
 tools/perf/Documentation/perf-stat.txt |  5 +++--
 tools/perf/builtin-list.c              | 18 ++++++++++++++++--
 tools/perf/builtin-probe.c             |  8 +++-----
 tools/perf/builtin-record.c            | 16 ++++++++++++----
 tools/perf/builtin-stat.c              | 13 +++++++++----
 tools/perf/builtin-top.c               | 10 ++++++++--
 tools/perf/util/hist.c                 |  2 +-
 tools/perf/util/machine.c              |  2 +-
 tools/perf/util/pmu.c                  |  3 ++-
 tools/perf/util/probe-event.c          |  8 +++++---
 tools/perf/util/session.c              |  2 +-
 tools/perf/util/session.h              |  2 ++
 13 files changed, 65 insertions(+), 26 deletions(-)

From: Namhyung Kim <[email protected]>

A previous patch added a synthesized comm event for forked child process but it missed that the event should contain area for sample_id_hdr at the end. It worked by accident since the perf_event union contains bigger event structs like mmap_events.

This patch fixes it by dynamically allocating event struct including those area like in perf_event__synthesize_thread_map().

---
 tools/perf/builtin-record.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

index a01c8ae1ee07..5e01c070dbf2 100644
@@ -637,17 +637,25 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 	 * Let the child rip
 	 */
 	if (forks) {
-		union perf_event event;
+		union perf_event *event;
+
+		event = malloc(sizeof(event->comm) + machine->id_hdr_size);
+		if (event == NULL) {
+			err = -ENOMEM;
+			goto out_child;
+		}
+
 		/*
 		 * Some H/W events are generated before COMM event
 		 * which is emitted during exec(), so perf script
 		 * cannot see a correct process name for those events.
 		 * Synthesize COMM event to prevent it.
 		 */
-		perf_event__synthesize_comm(tool, &event,
+		perf_event__synthesize_comm(tool, event,
 					    rec->evlist->workload.pid,
 					    process_synthesized_event,
 					    machine);
+		free(event);
 
 		perf_evlist__start_workload(rec->evlist);
 	}

2.1.0

From: Namhyung Kim <[email protected]>

The perf top uses 'dso,symbol' sort keys by default so it overlooked a problem in task's comm resolving. When the sort key contains 'comm', some task's comm is not shown properly. This is because the perf_top__mmap_read_idx() checks the cpumode value improperly.

The cpumode value of non-sample events are 0 (PERF_RECORD_MISC_CPUMODE_ UNKNOWN) so the events will be ignored by the switch statement. This patch allows it for non-sample events.

---
 tools/perf/builtin-top.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

index 38d4d6cac823..ae4c6420300b 100644
@@ -857,9 +857,12 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx)
 			 * TODO: we don't process guest user from host side
 			 * except simple counting.
 			 */
-			/* Fall thru */
-		default:
 			goto next_event;
+		default:
+			if (event->header.type == PERF_RECORD_SAMPLE)
+				goto next_event;
+			machine = &session->machines.host;
+			break;
 		}
 
 

2.1.0

From: Namhyung Kim <[email protected]>

The perf top didn't add the idle/swapper thread to the machine's thread list and its comm was displayed as ':0'. Fix it.

---
 tools/perf/builtin-top.c  | 3 +++
 tools/perf/util/session.c | 2 +-
 tools/perf/util/session.h | 2 ++
 3 files changed, 6 insertions(+), 1 deletion(-)

index ae4c6420300b..6f641fd68296 100644
@@ -964,6 +964,9 @@ static int __cmd_top(struct perf_top *top)
 	if (ret)
 		goto out_delete;
 
+	if (perf_session__register_idle_thread(top->session) == NULL)
+		goto out_delete;
+
 	machine__synthesize_threads(&top->session->machines.host, &opts->target,
 				    top->evlist->threads, false, opts->proc_map_timeout);
 

index 84a02eae4394..428149bc64d2 100644
@@ -1311,7 +1311,7 @@ struct thread *perf_session__findnew(struct perf_session *session, pid_t pid)
 	return machine__findnew_thread(&session->machines.host, -1, pid);
 }
 
-static struct thread *perf_session__register_idle_thread(struct perf_session *session)
+struct thread *perf_session__register_idle_thread(struct perf_session *session)
 {
 	struct thread *thread;
 

index b44afc75d1cc..3e900c0efc73 100644
@@ -89,6 +89,8 @@ struct machine *perf_session__findnew_machine(struct perf_session *session, pid_
 }
 
 struct thread *perf_session__findnew(struct perf_session *session, pid_t pid);
+struct thread *perf_session__register_idle_thread(struct perf_session *session);
+
 size_t perf_session__fprintf(struct perf_session *session, FILE *fp);
 
 size_t perf_session__fprintf_dsos(struct perf_session *session, FILE *fp);

2.1.0

From: Namhyung Kim <[email protected]>

The patch f9db0d0f1b2c ("perf callchain: Allow disabling call graphs per event") added an ability to enable/disable callchain recording per event. But it had a problem when the enablement setting is changed at 'perf report' time using -g/--call-graph option.

For example, the following scenario will get a segfault.

  $ perf record -ag sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.500 MB perf.data (2555 samples) ]

  $ perf report -g none
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x53a98a]
  /usr/lib/libc.so.6(+0x335af)[0x7f4e91df95af]

This is because callchain_param.sort() callback was not set but it tried to call the function as it had the PERF_SAMPLE_CALLCHAIN bit.

---
 tools/perf/util/hist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 0cad9e07c5b4..c346b331b892 100644
@@ -1151,7 +1151,7 @@ void hists__output_resort(struct hists *hists, struct ui_progress *prog)
 	struct perf_evsel *evsel = hists_to_evsel(hists);
 	bool use_callchain;
 
-	if (evsel && !symbol_conf.show_ref_callgraph)
+	if (evsel && symbol_conf.use_callchain && !symbol_conf.show_ref_callgraph)
 		use_callchain = evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN;
 	else
 		use_callchain = symbol_conf.use_callchain;

2.1.0

From: Adrian Hunter <[email protected]>

Adjust the validation to allow for max_stack greater than PERF_MAX_STACK_DEPTH.

---
 tools/perf/util/machine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 76fe167c359e..5ef90be2a249 100644
@@ -1831,7 +1831,7 @@ static int thread__resolve_callchain_sample(struct thread *thread,
 	}
 
 check_calls:
-	if (chain->nr > PERF_MAX_STACK_DEPTH) {
+	if (chain->nr > PERF_MAX_STACK_DEPTH && (int)chain->nr > max_stack) {
 		pr_warning("corrupted callchain. skipping...\n");
 		return 0;
 	}

2.1.0

From: Arnaldo Carvalho de Melo <[email protected]>

Before:

  # perf list _alloc_ | head -10
  #

After:

  # perf list _alloc_ | head -10
    ext4:ext4_alloc_da_blocks                          [Tracepoint event]
    ext4:ext4_get_implied_cluster_alloc_exit           [Tracepoint event]
    kmem:kmem_cache_alloc_node                         [Tracepoint event]
    kmem:mm_page_alloc_extfrag                         [Tracepoint event]
    kmem:mm_page_alloc_zone_locked                     [Tracepoint event]
    xen:xen_mmu_alloc_ptpage                           [Tracepoint event]
  #

And it works for all types of events:

  # perf list br

List of pre-defined events (to be used in -e):

branch-instructions OR branches [Hardware event]
branch-misses [Hardware event]

branch-load-misses [Hardware cache event]
branch-loads [Hardware cache event]

branch-instructions OR cpu/branch-instructions/ [Kernel PMU event]
branch-misses OR cpu/branch-misses/ [Kernel PMU event]

filelock:break_lease_block [Tracepoint event]
filelock:break_lease_noblock [Tracepoint event]
filelock:break_lease_unblock [Tracepoint event]
syscalls:sys_enter_brk [Tracepoint event]
syscalls:sys_exit_brk [Tracepoint event]

#

---
 tools/perf/Documentation/perf-list.txt |  2 ++
 tools/perf/builtin-list.c              | 18 ++++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

index bada8933fdd4..ad60c6ea1997 100644
@@ -125,6 +125,8 @@ To limit the list use:
 . If none of the above is matched, it will apply the supplied glob to all
   events, printing the ones that match.
 
+. As a last resort, it will do a substring search in all event names.
+
 One or more types can be used at the same time, listing the events for the
 types specified.
 

index 602414040344..bf679e2c978b 100644
@@ -45,6 +45,8 @@ int cmd_list(int argc, const char **argv, const char *prefix __maybe_unused)
 	}
 
 	for (i = 0; i < argc; ++i) {
+		char *sep, *s;
+
 		if (strcmp(argv[i], "tracepoint") == 0)
 			print_tracepoint_events(NULL, NULL, raw_dump);
 		else if (strcmp(argv[i], "hw") == 0 ||

@@ -60,8 +62,7 @@ int cmd_list(int argc, const char **argv, const char *prefix __maybe_unused)
 			print_hwcache_events(NULL, raw_dump);
 		else if (strcmp(argv[i], "pmu") == 0)
 			print_pmu_events(NULL, raw_dump);
-		else {
-			char *sep = strchr(argv[i], ':'), *s;
+		else if ((sep = strchr(argv[i], ':')) != NULL) {
 			int sep_idx;
 
 			if (sep == NULL) {

@@ -76,6 +77,19 @@ int cmd_list(int argc, const char **argv, const char *prefix __maybe_unused)
 			s[sep_idx] = '\0';
 			print_tracepoint_events(s, s + sep_idx + 1, raw_dump);
 			free(s);
+		} else {
+			if (asprintf(&s, "*%s*", argv[i]) < 0) {
+				printf("Critical: Not enough memory! Trying to continue...\n");
+				continue;
+			}
+			print_symbol_events(s, PERF_TYPE_HARDWARE,
+					    event_symbols_hw, PERF_COUNT_HW_MAX, raw_dump);
+			print_symbol_events(s, PERF_TYPE_SOFTWARE,
+					    event_symbols_sw, PERF_COUNT_SW_MAX, raw_dump);
+			print_hwcache_events(s, raw_dump);
+			print_pmu_events(s, raw_dump);
+			print_tracepoint_events(NULL, s, raw_dump);
+			free(s);
 		}
 	}
 	return 0;

2.1.0

From: Arnaldo Carvalho de Melo <[email protected]>

Some PMUs, like the 'intel_bts' one can be used as an event name, i.e.:

	$ perf record -e intel_bts:// usleep 1

Is a valid event name.

But the code printing such PMUs was not honouring the 'event_glob' parameter, so the following line was always appearing:

  $ intel_bts//                                        [Kernel PMU event]

Fix it:

  $ [acme@felicio linux]$ perf list data

List of pre-defined events (to be used in -e):

uncore_imc/data_reads/ [Kernel PMU event]
uncore_imc/data_writes/ [Kernel PMU event]

$

---
 tools/perf/util/pmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index 41a356ba3cfe..e4b173dec4b9 100644
@@ -1008,7 +1008,8 @@ void print_pmu_events(const char *event_glob, bool name_only)
 				goto out_enomem;
 			j++;
 		}
-		if (pmu->selectable) {
+		if (pmu->selectable &&
+		    (event_glob == NULL || strglobmatch(pmu->name, event_glob))) {
 			char *s;
 			if (asprintf(&s, "%s//", pmu->name) < 0)
 				goto out_enomem;

2.1.0

From: Masami Hiramatsu <[email protected]>

Allow probing on kernel modules when 'perf' is built without debuginfo support.

Currently perf-probe --module requires linking with libdw, but this doesn't make sense.

E.g.
----

  # make NO_DWARF=1
  # ./perf probe -m pcspkr pcspkr_event%return
    Error: unknown switch `m'
  ----

With this patch
----

  # ./perf probe -m pcspkr pcspkr_event%return
  Added new event:
    probe:pcspkr_event   (on pcspkr_event%return in pcspkr)

You can now use it in all perf tools, such as:

perf record -e probe:pcspkr_event -aR sleep 1
----

---
 tools/perf/builtin-probe.c    | 8 +++-----
 tools/perf/util/probe-event.c | 8 +++++---
 2 files changed, 8 insertions(+), 8 deletions(-)

index f7882ae9ebc6..530c3a28a58c 100644
@@ -182,10 +182,8 @@ static int opt_set_target(const struct option *opt, const char *str,
 	if  (str) {
 		if (!strcmp(opt->long_name, "exec"))
 			params.uprobes = true;
-#ifdef HAVE_DWARF_SUPPORT
 		else if (!strcmp(opt->long_name, "module"))
 			params.uprobes = false;
-#endif
 		else
 			return ret;
 

@@ -490,9 +488,6 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
 		   "file", "vmlinux pathname"),
 	OPT_STRING('s', "source", &symbol_conf.source_prefix,
 		   "directory", "path to kernel source"),
-	OPT_CALLBACK('m', "module", NULL, "modname|path",
-		"target module name (for online) or path (for offline)",
-		opt_set_target),
 	OPT_BOOLEAN('\0', "no-inlines", &probe_conf.no_inlines,
 		"Don't search inlined functions"),
 #endif

@@ -509,6 +504,9 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
 		     opt_set_filter),
 	OPT_CALLBACK('x', "exec", NULL, "executable|path",
 			"target executable name or path", opt_set_target),
+	OPT_CALLBACK('m', "module", NULL, "modname|path",
+		"target module name (for online) or path (for offline)",
+		opt_set_target),
 	OPT_BOOLEAN(0, "demangle", &symbol_conf.demangle,
 		    "Enable symbol demangling"),
 	OPT_BOOLEAN(0, "demangle-kernel", &symbol_conf.demangle_kernel,

index 3010abc071ff..b51a8bfb40f9 100644
@@ -2543,7 +2543,8 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
 		goto out;
 	}
 
-	if (!pev->uprobes && !pp->retprobe) {
+	/* Note that the symbols in the kmodule are not relocated */
+	if (!pev->uprobes && !pp->retprobe && !pev->target) {
 		reloc_sym = kernel_get_ref_reloc_sym();
 		if (!reloc_sym) {
 			pr_warning("Relocated base symbol is not found!\n");

@@ -2580,8 +2581,9 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
 		}
 		/* Add one probe point */
 		tp->address = map->unmap_ip(map, sym->start) + pp->offset;
-		/* If we found a wrong one, mark it by NULL symbol */
-		if (!pev->uprobes &&
+
+		/* Check the kprobe (not in module) is within .text  */
+		if (!pev->uprobes && !pev->target &&
 		    kprobe_warn_out_range(sym->name, tp->address)) {
 			tp->symbol = NULL;	/* Skip it */
 			skipped++;

2.1.0

From: Yang Shi <[email protected]>

When run "perf record -e", the number of samples showed up is wrong on some 32 bit systems, i.e. powerpc and arm.

For example, run the below commands on 32 bit powerpc:

perf probe -x /lib/libc.so.6 malloc
perf record -e probe_libc:malloc -a ls perf.data
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.036 MB perf.data (13829241621624967218 samples) ]

Actually, "perf script" just shows 21 samples. The number of samples is also absurd since samples is long type, but it is printed as PRIu64.

Build test ran on x86-64, x86, aarch64, arm, mips, ppc and ppc64.

---
 tools/perf/builtin-record.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

index 5e01c070dbf2..24ace2f318c1 100644
@@ -49,7 +49,7 @@ struct record {
 	int			realtime_prio;
 	bool			no_buildid;
 	bool			no_buildid_cache;
-	long			samples;
+	unsigned long long	samples;
 };
 
 static int record__write(struct record *rec, void *bf, size_t size)

@@ -667,7 +667,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 
 	auxtrace_snapshot_enabled = 1;
 	for (;;) {
-		int hits = rec->samples;
+		unsigned long long hits = rec->samples;
 
 		if (record__mmap_read_all(rec) < 0) {
 			auxtrace_snapshot_enabled = 0;

2.1.0

From: Kan Liang <[email protected]>

The --interval-print parameter was limited to 100ms. However, for example, 10ms is required to do sophisticated bandwidth analysis using uncore events.

The test shows that the overhead of the system-wide uncore monitoring with 10ms interval is only ~2%. So this patch reduces the minimal interval-print allowd to 10ms.

But 10ms may not work well for all cases. For example, when the cpus/threads number is very large, for system-wide core event monitoring the overhead could be high.

To handle this issue, a warning will be displayed when the interval-print is set between 10ms to 100ms. So users can make a decision according to their specific cases.

 # perf stat -e uncore_imc_1/cas_count_read/ -a --interval-print 10 -- sleep 1

print interval < 100ms. The overhead percentage could be high in some cases. Please proceed with caution.
# time counts unit events

      0.010200451               0.10 MiB  uncore_imc_1/cas_count_read/
      0.020475117               0.02 MiB  uncore_imc_1/cas_count_read/
      0.030692800               0.01 MiB  uncore_imc_1/cas_count_read/
      0.040948161               0.02 MiB  uncore_imc_1/cas_count_read/
      0.051159564               0.00 MiB  uncore_imc_1/cas_count_read/

---
 tools/perf/Documentation/perf-stat.txt |  5 +++--
 tools/perf/builtin-stat.c              | 13 +++++++++----
 2 files changed, 12 insertions(+), 6 deletions(-)

index 47469abdcc1c..4e074a660826 100644
@@ -128,8 +128,9 @@ perf stat --repeat 10 --null --sync --pre 'make -s O=defconfig-build/clean' -- m
 
 -I msecs::
 --interval-print msecs::
-	Print count deltas every N milliseconds (minimum: 100ms)
-	example: perf stat -I 1000 -e cycles -a sleep 5
+Print count deltas every N milliseconds (minimum: 10ms)
+The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals.  Use with caution.
+	example: 'perf stat -I 1000 -e cycles -a sleep 5'
 
 --per-socket::
 Aggregate counts per processor socket for system-wide mode measurements.  This

index a96fb5c3bedb..5ef88f760b12 100644
@@ -1179,7 +1179,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 	OPT_STRING(0, "post", &post_cmd, "command",
 			"command to run after to the measured command"),
 	OPT_UINTEGER('I', "interval-print", &stat_config.interval,
-		    "print counts at regular interval in ms (>= 100)"),
+		    "print counts at regular interval in ms (>= 10)"),
 	OPT_SET_UINT(0, "per-socket", &stat_config.aggr_mode,
 		     "aggregate counts per processor socket", AGGR_SOCKET),
 	OPT_SET_UINT(0, "per-core", &stat_config.aggr_mode,

@@ -1332,9 +1332,14 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 		thread_map__read_comms(evsel_list->threads);
 
 	if (interval && interval < 100) {
-		pr_err("print interval must be >= 100ms\n");
-		parse_options_usage(stat_usage, options, "I", 1);
-		goto out;
+		if (interval < 10) {
+			pr_err("print interval must be >= 10ms\n");
+			parse_options_usage(stat_usage, options, "I", 1);
+			goto out;
+		} else
+			pr_warning("print interval < 100ms. "
+				   "The overhead percentage could be high in some cases. "
+				   "Please proceed with caution.\n");
 	}
 
 	if (perf_evlist__alloc_stats(evsel_list, interval))

2.1.0

Pulled, thanks a lot Arnaldo!

Btw., incidentally I noticed an UI detail: in the 'perf report' and 'perf top' TUI, PageUp does not move the cursor to the topmost line, it stays at whatever partial page position it is.

I think it would be better to behave here like good editors do: PageUp in the first partial page moves to the first line (like 'Home') - and PageDown on the last page of output moves to the last line (like 'End').

Btw., even popular TUI editors get this wrong sometimes:

- 'nano' (joe clone, popular mail editor) gets this right in both directions.

- 'vim' behaves this way on PageDown, but not on PageUp. Nor does it recognize Home/End, only Ctrl-Home/End works.

- 'emacs (e3 package) gets the PageUp/PageDown behavior right, but no Home/End key combo works (and exiting the editor is painful as well ;-)

Thanks,

Ingo