linux-kernel - Re: [PATCH] perf test: Test case 27 fails on s390 and non-x86 platforms

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Date:   Tue, 2 Mar 2021 15:48:53 +0100
From:   Thomas Richter <tmricht@...ux.ibm.com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org
Cc:     svens@...ux.ibm.com, gor@...ux.ibm.com, sumanthk@...ux.ibm.com,
        heiko.carstens@...ibm.com,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
Subject: Re: [PATCH] perf test: Test case 27 fails on s390 and non-x86
 platforms

On 3/2/21 3:03 PM, Liang, Kan wrote:
> 
> + Athira Rajeev
> 
> On 3/2/2021 8:31 AM, Thomas Richter wrote:
>> Executing perf test 27 fails on s390:
>>   [root@...lp46 perf]# ./perf test -Fv 27
>>   27: Sample parsing
>>   --- start ---
>>   ---- end ----
>>   Sample parsing: FAILED!
>>   [root@...lp46 perf]#
>>
>> The root cause is
>> commit c7444297fd3769 ("perf test: Support PERF_SAMPLE_WEIGHT_STRUCT")
>> This commit introduced a test case for PERF_SAMPLE_WEIGHT_STRUCT
>> but does not adjust non-x86 weak linkage functions.
>>
>> The error is in test__sample_parsing() --> do_test()
>> Function do_test() defines two structures of type struct perf_sample named
>> sample and sample_out. The first sets member sample.ins_lat = 117
>>
>> Structure sample_out is constructed dynamically using functions
>> perf_event__synthesize_sample() and evsel__parse_sample().
>> Both functions have an x86 specific function version which sets member
>> ins_lat. The weak common functions do not set member ins_lat.
>>
> 
> I don't think Power supports the instruction latency. As a request from Athira Rajeev, I moved the PERF_SAMPLE_WEIGHT_STRUCT to the X86 specific codes.
> https://lore.kernel.org/lkml/D97FEF4F-DD88-4760-885E-9A6161A9B48B@linux.vnet.ibm.com/
> https://lore.kernel.org/lkml/1612540912-6562-1-git-send-email-kan.liang@linux.intel.com/
> 
> I don't think we want to add the ins_lat back in the weak common functions.
> 
> Could you please update the perf test and don't apply the PERF_SAMPLE_WEIGHT_STRUCT for the non-X86 platform?

I used offical linux git tree
 [root@...lp46 perf]# git tag | fgrep 5.12
v5.12-rc1
[root@...lp46 perf]# 

So this change is in the pipe. I do not plan to revert individual patches.
> 
> 
>> Later in function samples_same() both data in variable sample and sample_out
>> are compared. The comparison fails because sample.ins_lat is 117
>> and samples_out.ins_lat is 0, the weak functions never set member ins_lat.
>>
>> Output after:
>>   [root@...lp46 perf]# ./perf test -Fv 27
>>   27: Sample parsing
>>   --- start ---
>>   ---- end ----
>>   Sample parsing: Ok
>> [root@...lp46 perf]#
>>
>> Fixes:
>> commit c7444297fd3769 ("perf test: Support PERF_SAMPLE_WEIGHT_STRUCT")
> 
> I think the regression should start from
> commit fbefe9c2f87f ("perf tools: Support arch specific PERF_SAMPLE_WEIGHT_STRUCT processing")
> 
> 
> Thanks,
> Kan

Kan, 

I do not follow you. Your commit c7444297fd3769d10c7ffb52c81d71503b3e268f
adds this line

@@ -242,6 +245,7 @@ static int do_test(u64 sample_type, u64 sample_regs, u64 read_format)
                .cgroup         = 114,
                .data_page_size = 115,
                .code_page_size = 116,
+               .ins_lat        = 117,

And this assignment 117 breaks the test. As mentioned before, member ins_lat is never touched
by the weak functions. 

-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
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