linux-kernel - Re: [PATCH RFC 5/7] perf pmu: Support matching by sysid

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Date:   Mon, 10 Feb 2020 16:22:56 +0000
From:   John Garry <john.garry@...wei.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <namhyung@...nel.org>, <will@...nel.org>, <ak@...ux.intel.com>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <suzuki.poulose@....com>,
        <james.clark@....com>, <zhangshaokun@...ilicon.com>,
        <robin.murphy@....com>
Subject: Re: [PATCH RFC 5/7] perf pmu: Support matching by sysid

Hi jirka,

> 
>> +		fclose(file);
>> +		pr_debug("gets failed for file %s\n", path);
>> +		free(buf);
>> +		return NULL;
>> +	}
>> +	fclose(file);
>> +
>> +	/* Remove any whitespace, this could be from ACPI HID */
>> +	s = strlen(buf);
>> +	for (i = 0; i < s; i++) {
>> +		if (buf[i] == ' ') {
>> +			buf[i] = 0;
>> +			break;
>> +		};
>> +	}
>> +
>> +	return buf;
>> +}
>> +

I have another series to add kernel support for a system identifier 
sysfs entry, which I sent after this series:

https://lore.kernel.org/linux-acpi/1580210059-199540-1-git-send-email-john.garry@huawei.com/

It is different to what I am relying on here - it uses a kernel soc 
driver for firmware ACPI PPTT identifier. Progress is somewhat blocked 
at the moment however and I may have to use a different method:

https://lore.kernel.org/linux-acpi/20200128123415.GB36168@bogus/

>> +static char *perf_pmu__getsysid(void)
>> +{
>> +	char *sysid;
>> +	static bool printed;
>> +
>> +	sysid = getenv("PERF_SYSID");
>> +	if (sysid)
>> +		sysid = strdup(sysid);
>> +
>> +	if (!sysid)
>> +		sysid = get_sysid_str();
>> +	if (!sysid)
>> +		return NULL;
>> +
>> +	if (!printed) {
>> +		pr_debug("Using SYSID %s\n", sysid);
>> +		printed = true;
>> +	}
>> +	return sysid;
>> +}
> 
> this part is getting complicated and AFAIK we have no tests for it
> 
> if you could think of any tests that'd be great.. Perhaps we could
> load 'our' json test files and check appropriate events/aliasses
> via in pmu object.. or via parse_events interface.. those test aliases
> would have to be part of perf, but we have tests compiled in anyway

Sorry, I don't fully follow.

Are you suggesting that we could load the specific JSONs tables for a 
system from the host filesystem?

Thanks,
John