[Powertop] patch: tell user if the system is running out of FDs

[Jaroslav Skarvada <jskarvad at redhat.com>]

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Hi,

complex servers can run out of FDs easily (due to perf).
In such case tell user that more FDs are needed instead
of the generic message (that kernel doesn't support
the perf)

regards

Jaroslav

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diff -up powertop-2.4/src/perf/perf.cpp.orig powertop-2.4/src/perf/perf.cpp
--- powertop-2.4/src/perf/perf.cpp.orig	2013-01-31 16:39:27.000000000 -0500
+++ powertop-2.4/src/perf/perf.cpp	2013-09-19 10:36:02.298839248 -0400
@@ -26,6 +26,7 @@
 #include <iostream>
 #include <fstream>
 
+#include <errno.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -72,6 +73,7 @@ void perf_event::create_perf_event(char 
 {
 	struct perf_event_attr attr;
 	int ret;
+	int err;
 
 	struct {
 		__u64 count;
@@ -107,10 +109,15 @@ void perf_event::create_perf_event(char 
 	perf_fd = sys_perf_event_open(&attr, -1, _cpu, -1, 0);
 
 	if (perf_fd < 0) {
+		err = errno;
 		reset_display();
-		fprintf(stderr, _("PowerTOP %s needs the kernel to support the 'perf' subsystem\n"), POWERTOP_VERSION);
-		fprintf(stderr, _("as well as support for trace points in the kernel:\n"));
-		fprintf(stderr, "CONFIG_PERF_EVENTS=y\nCONFIG_PERF_COUNTERS=y\nCONFIG_TRACEPOINTS=y\nCONFIG_TRACING=y\n");
+		if (err == EMFILE)
+			fprintf(stderr, _("Too many open files, please increase the limit of open file descriptors.\n"));
+		else {
+			fprintf(stderr, _("PowerTOP %s needs the kernel to support the 'perf' subsystem\n"), POWERTOP_VERSION);
+			fprintf(stderr, _("as well as support for trace points in the kernel:\n"));
+			fprintf(stderr, "CONFIG_PERF_EVENTS=y\nCONFIG_PERF_COUNTERS=y\nCONFIG_TRACEPOINTS=y\nCONFIG_TRACING=y\n");
+		}
 		exit(EXIT_FAILURE);
 	}
 	if (read(perf_fd, &read_data, sizeof(read_data)) == -1) {