Subject: Re: perf top for arm64?

From: Jiri Olsa <[email-masked]>
Date: Tue, 10 Dec 2019 17:36:55 +0100

On Tue, Dec 10, 2019 at 04:13:49PM +0000, John Garry wrote:
> 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

there was recent change that check on cpuid and quits:
  608127f73779 perf top: Initialize perf_env->cpuid, needed by the per arch annotation init routine

Arnaldo,
maybe this should be just a warning/info, because it seems to be related
to annotations only..?

get_cpuid is defined only for s390/x86/powerpc, so I guess it won't work
on the rest as well

jirka

> 
> 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 <[email-masked]>
> 
> 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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