linux-kernel - [PATCH] tools/power turbostat: Increase the limit for fd opened

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Date:   Fri, 22 Sep 2023 09:28:23 +0000
From:   Wyes Karny <wyes.karny@....com>
To:     <lenb@...nel.org>
CC:     <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Wyes Karny <wyes.karny@....com>
Subject: [PATCH] tools/power turbostat: Increase the limit for fd opened

When running turbostat, a system with 512 cpus reaches the limit for
maximum number of file descriptors that can be opened. To solve this
problem, the limit is raised to 2^15, which is a large enough number.

Below data is collected from AMD server systems while running turbostat:

|-----------+-------------------------------|
| # of cpus | # of opened fds for turbostat |
|-----------+-------------------------------|
| 128       | 260                           |
|-----------+-------------------------------|
| 192       | 388                           |
|-----------+-------------------------------|
| 512       | 1028                          |
|-----------+-------------------------------|

So, the new max limit would be sufficient up to 2^14 cpus.

Signed-off-by: Wyes Karny <wyes.karny@....com>
---
 tools/power/x86/turbostat/turbostat.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 9a10512e3407..23f1fe58289a 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -6717,6 +6717,18 @@ void cmdline(int argc, char **argv)
 	}
 }
 
+void set_rlimit(void)
+{
+	struct rlimit limit;
+
+	limit.rlim_cur = 0x8000;
+	limit.rlim_max = 0x8000;
+
+	if (setrlimit(RLIMIT_NOFILE, &limit) < 0) {
+		err(1, "Failed to set rlimit");
+	}
+}
+
 int main(int argc, char **argv)
 {
 	outf = stderr;
@@ -6729,6 +6741,9 @@ int main(int argc, char **argv)
 
 	probe_sysfs();
 
+	if (!getuid())
+		set_rlimit();
+
 	turbostat_init();
 
 	msr_sum_record();
-- 
2.34.1