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Subjectperf top for arm64?
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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@huawei.com>

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;
+}
+

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