[PATCH v2 1/2] tools/power turbostat: read from pipes too

[PATCH v2 1/2] tools/power turbostat: read from pipes too

[Artem Bityutskiy]

From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Commit '47936f944e78 tools/power turbostat: fix printing on input' make
a valid fix, but it completely disabled piped stdin support, which is
a valuable use-case. Indeed, if stdin is a pipe, turbostat won't read
anything from it, so it becomes impossible to get turbostat output at
user-defined moments, instead of the regular intervals.

There is no reason why this should works for terminals, but not for
pipes. This patch improves the situation. Instead of ignoring pipes, we
read data from them but gracefully handle the EOF case.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
 tools/power/x86/turbostat/turbostat.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

---
Changelog:

v2: Clean up commit message.

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 75fc4fb9901c..573230a774cd 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -100,6 +100,7 @@ unsigned int has_hwp_epp;		/* IA32_HWP_REQUEST[bits 31:24] */
 unsigned int has_hwp_pkg;		/* IA32_HWP_REQUEST_PKG */
 unsigned int has_misc_feature_control;
 unsigned int first_counter_read = 1;
+int ignore_stdin = 0;
 
 #define RAPL_PKG		(1 << 0)
 					/* 0x610 MSR_PKG_POWER_LIMIT */
@@ -3005,26 +3006,37 @@ void setup_signal_handler(void)
 
 void do_sleep(void)
 {
-	struct timeval select_timeout;
+	struct timeval tout;
+	struct timespec rest;
 	fd_set readfds;
 	int retval;
 
 	FD_ZERO(&readfds);
 	FD_SET(0, &readfds);
 
-	if (!isatty(fileno(stdin))) {
+	if (ignore_stdin) {
 		nanosleep(&interval_ts, NULL);
 		return;
 	}
 
-	select_timeout = interval_tv;
-	retval = select(1, &readfds, NULL, NULL, &select_timeout);
+	tout = interval_tv;
+	retval = select(1, &readfds, NULL, NULL, &tout);
 
 	if (retval == 1) {
 		switch (getc(stdin)) {
 		case 'q':
 			exit_requested = 1;
 			break;
+		case EOF:
+			/*
+			 * 'stdin' is a pipe closed on the other end. There
+			 * won't be any further input.
+			 */
+			ignore_stdin = 1;
+			/* Sleep the rest of the time */
+			rest.tv_sec = (tout.tv_sec + tout.tv_usec / 1000000);
+			rest.tv_nsec = (tout.tv_usec % 1000000) * 1000;
+			nanosleep(&rest, NULL);
 		}
 		/* make sure this manually-invoked interval is at least 1ms long */
 		nanosleep(&one_msec, NULL);
-- 
2.20.1

[PATCH v2 2/2] tools/power turbostat: do not enforce 1ms

[Artem Bityutskiy]

From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

Turbostat works by taking a snapshot of counters, sleeping, taking another
snapshot, calculating deltas, and printing out the table.

The sleep time is controlled via -i option or by user sending a signal or a
character to stdin. In the latter case, turbostat always adds 1 ms
sleep before it reads the counters, in order to avoid larger imprecisions
in the results in prints.

While the 1 ms delay may be a good idea for a "dumb" user, it is a
problem for an "aware" user. I do thousands and thousands of measurements
over a short period of time (like 2ms), and turbostat unconditionally adds
a 1ms to my interval, so I cannot get what I really need.

This patch removes the unconditional 1ms sleep. This is an expert user
tool, after all, and non-experts will unlikely ever use it in the non-fixed
interval mode anyway, so I think it is OK to remove the 1ms delay.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
 tools/power/x86/turbostat/turbostat.c | 5 -----
 1 file changed, 5 deletions(-)

---
Changelog:

v2: Clean up commit message.

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 573230a774cd..57e236187cdb 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -39,7 +39,6 @@ FILE *outf;
 int *fd_percpu;
 struct timeval interval_tv = {5, 0};
 struct timespec interval_ts = {5, 0};
-struct timespec one_msec = {0, 1000000};
 unsigned int num_iterations;
 unsigned int debug;
 unsigned int quiet;
@@ -2986,8 +2985,6 @@ static void signal_handler (int signal)
 			fprintf(stderr, "SIGUSR1\n");
 		break;
 	}
-	/* make sure this manually-invoked interval is at least 1ms long */
-	nanosleep(&one_msec, NULL);
 }
 
 void setup_signal_handler(void)
@@ -3038,8 +3035,6 @@ void do_sleep(void)
 			rest.tv_nsec = (tout.tv_usec % 1000000) * 1000;
 			nanosleep(&rest, NULL);
 		}
-		/* make sure this manually-invoked interval is at least 1ms long */
-		nanosleep(&one_msec, NULL);
 	}
 }
 
-- 
2.20.1