linux-kernel - [PATCH v2] tools/power turbostat: Increase the limit for fd opened

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Message-ID: <20231003050751.525932-1-wyes.karny@amd.com>
Date:   Tue, 3 Oct 2023 05:07:51 +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>,
        Doug Smythies <dsmythies@...us.net>
Subject: [PATCH v2] 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 (but this
also depends on how many counters are enabled).

Reviewed-by: Doug Smythies <dsmythies@...us.net>
Tested-by: Doug Smythies <dsmythies@...us.net>
Signed-off-by: Wyes Karny <wyes.karny@....com>
---
v1 -> v2:
- Take care of already higher rlim_max, rlim_curr
- Minor tweak in commit text

 tools/power/x86/turbostat/turbostat.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 9a10512e3407..1563a0ae7e4c 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -53,6 +53,8 @@
 #define	NAME_BYTES 20
 #define PATH_BYTES 128
 
+#define MAX_NOFILE 0x8000
+
 enum counter_scope { SCOPE_CPU, SCOPE_CORE, SCOPE_PACKAGE };
 enum counter_type { COUNTER_ITEMS, COUNTER_CYCLES, COUNTER_SECONDS, COUNTER_USEC };
 enum counter_format { FORMAT_RAW, FORMAT_DELTA, FORMAT_PERCENT };
@@ -6717,6 +6719,22 @@ void cmdline(int argc, char **argv)
 	}
 }
 
+void set_rlimit(void)
+{
+	struct rlimit limit;
+
+	if (getrlimit(RLIMIT_NOFILE, &limit) < 0)
+		err(1, "Failed to get rlimit");
+
+	if (limit.rlim_max < MAX_NOFILE)
+		limit.rlim_max = MAX_NOFILE;
+	if (limit.rlim_cur < MAX_NOFILE)
+		limit.rlim_cur = MAX_NOFILE;
+
+	if (setrlimit(RLIMIT_NOFILE, &limit) < 0)
+		err(1, "Failed to set rlimit");
+}
+
 int main(int argc, char **argv)
 {
 	outf = stderr;
@@ -6729,6 +6747,9 @@ int main(int argc, char **argv)
 
 	probe_sysfs();
 
+	if (!getuid())
+		set_rlimit();
+
 	turbostat_init();
 
 	msr_sum_record();
-- 
2.34.1