perf top for arm64?

[John Garry]

Hi all,

I find to my surprise that "perf top" does not work for arm64:

root@ubuntu:/home/john/linux# tools/perf/perf top
Couldn't read the cpuid for this machine: No such file or directory

That's v5.5-rc1 release.

It seems that we are just missing an arm64 version of get_cpuid() - with 
the patch below, I now get as hoped:

   PerfTop:   32857 irqs/sec  kernel:85.0%  exact:  0.0% lost: 0/0 
drop: 0/0 [4000Hz cycles],  (all, 64 CPUs)
-------------------------------------------------------------------------------

     8.99%  [kernel]          [k] arm_smmu_cmdq_issue_cmdlist
     5.80%  [kernel]          [k] __softirqentry_text_start
     4.49%  [kernel]          [k] _raw_spin_unlock_irqrestore
     3.48%  [kernel]          [k] el0_svc_common.constprop.2
     3.37%  [kernel]          [k] _raw_write_lock_irqsave
     3.28%  [kernel]          [k] __local_bh_enable_ip
     3.05%  [kernel]          [k] __blk_complete_request
     2.07%  [kernel]          [k] queued_spin_lock_slowpath
     1.93%  [vdso]            [.] 0x0000000000000484


Was this just missed? Or is there a good reason to omit?

Thanks,
John

--->8---

Subject: [PATCH] perf: Add perf top support for arm64

Copied from get_cpuid_str() essentially...

Signed-off-by: John Garry <john.garry@xxxxxxxxxx>

diff --git a/tools/perf/arch/arm64/util/header.c 
b/tools/perf/arch/arm64/util/header.c
index a32e4b72a98f..ecd1f86e29cc 100644
--- a/tools/perf/arch/arm64/util/header.c
+++ b/tools/perf/arch/arm64/util/header.c
@@ -1,10 +1,12 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <perf/cpumap.h>
+#include <util/cpumap.h>
 #include <internal/cpumap.h>
 #include <api/fs/fs.h>
 #include "debug.h"
 #include "header.h"
+#include <errno.h>

 #define MIDR "/regs/identification/midr_el1"
 #define MIDR_SIZE 19
@@ -12,6 +14,59 @@
 #define MIDR_VARIANT_SHIFT      20
 #define MIDR_VARIANT_MASK       (0xf << MIDR_VARIANT_SHIFT)

+int
+get_cpuid(char *buffer, size_t sz)
+{
+	char *buf = NULL;
+	char path[PATH_MAX];
+	const char *sysfs = sysfs__mountpoint();
+	int cpu;
+	u64 midr = 0;
+	FILE *file;
+
+	if (!sysfs)
+		return EINVAL;
+
+	buf = malloc(MIDR_SIZE);
+	if (!buf)
+		return EINVAL;
+
+	/* read midr from list of cpus mapped to this pmu */
+	for (cpu = 0; cpu < cpu__max_present_cpu(); cpu++) {
+		scnprintf(path, sz, "%s/devices/system/cpu/cpu%d"MIDR,
+				sysfs, cpu);
+
+		file = fopen(path, "r");
+		if (!file) {
+			pr_debug("fopen failed for file %s\n", path);
+			continue;
+		}
+
+		if (!fgets(buf, MIDR_SIZE, file)) {
+			fclose(file);
+			continue;
+		}
+		fclose(file);
+
+		/* Ignore/clear Variant[23:20] and
+		 * Revision[3:0] of MIDR
+		 */
+		midr = strtoul(buf, NULL, 16);
+		midr &= (~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK));
+		scnprintf(buffer, MIDR_SIZE, "0x%016lx", midr);
+		/* got midr break loop */
+		break;
+	}
+
+	if (!midr) {
+		pr_err("failed to get cpuid string\n");
+		free(buf);
+		return EINVAL;
+	}
+	return 0;
+}
+