On s390 the CPU Measurement Facility for counters now supports
2 PMUs named cpum_cf (CPU Measurement Facility for counters) and
cpum_cf_diag (CPU Measurement Facility for diagnostic counters)
for one and the same CPU.
Running command
[root@s35lp76 perf]# ./perf stat -e tx_c_tend \
-- ~/mytests/cf-tx-events 1
Measuring transactions
TX_C_TABORT_NO_SPECIAL: 0 expected:0
TX_C_TABORT_SPECIAL: 0 expected:0
TX_C_TEND: 1 expected:1
TX_NC_TABORT: 11 expected:11
TX_NC_TEND: 1 expected:1
Performance counter stats for '/root/mytests/cf-tx-events 1':
2 tx_c_tend
0.002120091 seconds time elapsed
0.000121000 seconds user
0.002127000 seconds sys
[root@s35lp76 perf]#
displays output which is unexpected (and wrong):
2 tx_c_tend
The test program definitely triggers only one transaction, as shown
in line 'TX_C_TEND: 1 expected:1'.
This is caused by the following call sequence:
pmu_lookup() scans and installs a PMU.
+--> pmu_aliases() parses all aliases in directory
.../<pmu-name>/events/* which are file names.
+--> pmu_aliases_parse() Read each file in directory and create
an new alias entry. This is done with
+--> perf_pmu__new_alias() and
+--> __perf_pmu__new_alias() which also check for
identical alias names.
After pmu_aliases() returns, a complete list of event names
for this pmu has been created. Now function
pmu_add_cpu_aliases() is called to add the events listed in the json
| files to the alias list of the cpu.
+--> perf_pmu__find_map() Returns a pointer to the json events.
Now function pmu_add_cpu_aliases() scans through all events listed
in the JSON files for this CPU.
Each json event pmu name is compared with the current PMU being
built up and if they mismatch, the json event is added to the
current PMUs alias list.
To avoid duplicate entries the following comparison is done:
if (!is_arm_pmu_core(name)) {
pname = pe->pmu ? pe->pmu : "cpu";
if (strncmp(pname, name, strlen(pname)))
continue;
}
The culprit is the strncmp() function.
Using current s390 PMU naming, the first PMU is 'cpum_cf'
and a long list of events is added, among them 'tx_c_tend'
When the second PMU named 'cpum_cf_diag' is added, only one event
named 'CF_DIAG' is added by the pmu_aliases() function.
Now function pmu_add_cpu_aliases() is invoked for PMU 'cpum_cf_diag'.
Since the CPUID string is the same for both PMUs, json file events
for PMU named 'cpum_cf' are added to the PMU 'cpm_cf_diag'
This happens because the strncmp() actually compares:
strncmp("cpum_cf", "cpum_cf_diag", 6);
The first parameter is the pmu name taken from the event in
the json file. The second parameter is the pmu name of the PMU
currently being built.
They are different, but the length of the compare only tests the
common prefix and this returns 0(true) when it should return false.
Now all events for PMU cpum_cf are added to the alias list for pmu
cpum_cf_diag.
Later on in function parse_events_add_pmu() the event 'tx_c_end' is
searched in all available PMUs and found twice, adding it two
times to the evsel_list global variable which is the root
of all events. This results in a counter value of 2 instead
of 1.
Output with this patch:
[root@s35lp76 perf]# ./perf stat -e tx_c_tend \
-- ~/mytests/cf-tx-events 1
Measuring transactions
TX_C_TABORT_NO_SPECIAL: 0 expected:0
TX_C_TABORT_SPECIAL: 0 expected:0
TX_C_TEND: 1 expected:1
TX_NC_TABORT: 11 expected:11
TX_NC_TEND: 1 expected:1
Performance counter stats for '/root/mytests/cf-tx-events 1':
1 tx_c_tend
0.001815365 seconds time elapsed
0.000123000 seconds user
0.001756000 seconds sys
[root@s35lp76 perf]#
Fixes: 292c34c10249 ("perf pmu: Fix core PMU alias list for X86 platform")
Signed-off-by: Thomas Richter <[email protected]>
Reviewed-by: Hendrik Brueckner <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: <[email protected]> # 4.18+
---
tools/perf/util/pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 7799788f662f..7e49baad304d 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -773,7 +773,7 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
if (!is_arm_pmu_core(name)) {
pname = pe->pmu ? pe->pmu : "cpu";
- if (strncmp(pname, name, strlen(pname)))
+ if (strcmp(pname, name))
continue;
}
--
2.14.3
On 2018-10-23 11:16 a.m., Thomas Richter wrote:
> On s390 the CPU Measurement Facility for counters now supports
> 2 PMUs named cpum_cf (CPU Measurement Facility for counters) and
> cpum_cf_diag (CPU Measurement Facility for diagnostic counters)
> for one and the same CPU.
>
> Running command
>
> [root@s35lp76 perf]# ./perf stat -e tx_c_tend \
> -- ~/mytests/cf-tx-events 1
>
Is tx_c_tend related to these ?
tx-abort OR cpu/tx-abort/ [Kernel PMU event]
tx-capacity OR cpu/tx-capacity/ [Kernel PMU event]
tx-commit OR cpu/tx-commit/ [Kernel PMU event]
tx-conflict OR cpu/tx-conflict/ [Kernel PMU event]
tx-start OR cpu/tx-start/ [Kernel PMU event]
> Measuring transactions
> TX_C_TABORT_NO_SPECIAL: 0 expected:0
> TX_C_TABORT_SPECIAL: 0 expected:0
> TX_C_TEND: 1 expected:1
> TX_NC_TABORT: 11 expected:11
> TX_NC_TEND: 1 expected:1
>
> Performance counter stats for '/root/mytests/cf-tx-events 1':
>
> 2 tx_c_tend
>
> 0.002120091 seconds time elapsed
>
> 0.000121000 seconds user
> 0.002127000 seconds sys
>
> [root@s35lp76 perf]#
>
> displays output which is unexpected (and wrong):
>
> 2 tx_c_tend
>
> The test program definitely triggers only one transaction, as shown
> in line 'TX_C_TEND: 1 expected:1'.
OK, something is done twice in perf stat, but should be done once.
>
> This is caused by the following call sequence:
>
> pmu_lookup() scans and installs a PMU.
> +--> pmu_aliases() parses all aliases in directory
> .../<pmu-name>/events/* which are file names.
> +--> pmu_aliases_parse() Read each file in directory and create
> an new alias entry. This is done with
> +--> perf_pmu__new_alias() and
> +--> __perf_pmu__new_alias() which also check for
> identical alias names.
>
> After pmu_aliases() returns, a complete list of event names
> for this pmu has been created. Now function
>
> pmu_add_cpu_aliases() is called to add the events listed in the json
> | files to the alias list of the cpu.
> +--> perf_pmu__find_map() Returns a pointer to the json events.
>
> Now function pmu_add_cpu_aliases() scans through all events listed
> in the JSON files for this CPU.
Are these JSON files temporary in nature ?
> Each json event pmu name is compared with the current PMU being
> built up and if they mismatch, the json event is added to the
> current PMUs alias list.
> To avoid duplicate entries the following comparison is done:
>
> if (!is_arm_pmu_core(name)) {
> pname = pe->pmu ? pe->pmu : "cpu";
> if (strncmp(pname, name, strlen(pname)))
> continue;
> }
Is this the test to know whether a PMU event must be added or not ?
>
> The culprit is the strncmp() function.
>
> Using current s390 PMU naming, the first PMU is 'cpum_cf'
> and a long list of events is added, among them 'tx_c_tend'
>
> When the second PMU named 'cpum_cf_diag' is added, only one event
> named 'CF_DIAG' is added by the pmu_aliases() function.
>
> Now function pmu_add_cpu_aliases() is invoked for PMU 'cpum_cf_diag'.
> Since the CPUID string is the same for both PMUs, json file events
> for PMU named 'cpum_cf' are added to the PMU 'cpm_cf_diag'
>
> This happens because the strncmp() actually compares:
>> strncmp("cpum_cf", "cpum_cf_diag", 6);
I fail to see how these argument values can be generated by this code:
pname = pe->pmu ? pe->pmu : "cpu";
if (strncmp(pname, name, strlen(pname)))
The 3rd argument is the length of the first argument, pname.
With "cpum_cf", it should be 7, not 6.
>
> The first parameter is the pmu name taken from the event in
> the json file. The second parameter is the pmu name of the PMU
> currently being built.
> They are different, but the length of the compare only tests the
> common prefix and this returns 0(true) when it should return false.
>
The 6 comes from strlen(pname). In that case, it is neither the length of
"cpum_cf" (7) or "cpum_cf_diag" (12).
> Now all events for PMU cpum_cf are added to the alias list for pmu
> cpum_cf_diag.
>
> Later on in function parse_events_add_pmu() the event 'tx_c_end' is
> searched in all available PMUs and found twice, adding it two
> times to the evsel_list global variable which is the root
> of all events. This results in a counter value of 2 instead
> of 1.
The counter value of 2 is 1 + 1 since both PMU events 'tx_c_end' that
were added got a +1.
>
> Output with this patch:
>
> [root@s35lp76 perf]# ./perf stat -e tx_c_tend \
> -- ~/mytests/cf-tx-events 1
> Measuring transactions
> TX_C_TABORT_NO_SPECIAL: 0 expected:0
> TX_C_TABORT_SPECIAL: 0 expected:0
> TX_C_TEND: 1 expected:1
> TX_NC_TABORT: 11 expected:11
> TX_NC_TEND: 1 expected:1
>
> Performance counter stats for '/root/mytests/cf-tx-events 1':
>
> 1 tx_c_tend
>
OK, now that's 1, like in your expected test value:
TX_C_TEND: 1 expected:1
> 0.001815365 seconds time elapsed
>
> 0.000123000 seconds user
> 0.001756000 seconds sys
>
> [root@s35lp76 perf]#
>
> Fixes: 292c34c10249 ("perf pmu: Fix core PMU alias list for X86 platform")
> Signed-off-by: Thomas Richter <[email protected]>
> Reviewed-by: Hendrik Brueckner <[email protected]>
> Cc: Kan Liang <[email protected]>
> Cc: <[email protected]> # 4.18+
> ---
> tools/perf/util/pmu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 7799788f662f..7e49baad304d 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -773,7 +773,7 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
>
> if (!is_arm_pmu_core(name)) {
> pname = pe->pmu ? pe->pmu : "cpu";
> - if (strncmp(pname, name, strlen(pname)))
> + if (strcmp(pname, name))
> continue;
> }
>
>
On 10/26/2018 05:04 PM, Sébastien Boisvert wrote:
> On 2018-10-23 11:16 a.m., Thomas Richter wrote:
>> On s390 the CPU Measurement Facility for counters now supports
>> 2 PMUs named cpum_cf (CPU Measurement Facility for counters) and
>> cpum_cf_diag (CPU Measurement Facility for diagnostic counters)
>> for one and the same CPU.
>>
>> Running command
>>
>> [root@s35lp76 perf]# ./perf stat -e tx_c_tend \
>> -- ~/mytests/cf-tx-events 1
>>
>
> Is tx_c_tend related to these ?
>
> tx-abort OR cpu/tx-abort/ [Kernel PMU event]
> tx-capacity OR cpu/tx-capacity/ [Kernel PMU event]
> tx-commit OR cpu/tx-commit/ [Kernel PMU event]
> tx-conflict OR cpu/tx-conflict/ [Kernel PMU event]
> tx-start OR cpu/tx-start/ [Kernel PMU event]
>
>
Yes, these are the transaction counters on intel platforms,
tx_c_tend is a transaction counter for s390.
>> Measuring transactions
>> TX_C_TABORT_NO_SPECIAL: 0 expected:0
>> TX_C_TABORT_SPECIAL: 0 expected:0
>> TX_C_TEND: 1 expected:1
>> TX_NC_TABORT: 11 expected:11
>> TX_NC_TEND: 1 expected:1
>>
>> Performance counter stats for '/root/mytests/cf-tx-events 1':
>>
>> 2 tx_c_tend
>>
>> 0.002120091 seconds time elapsed
>>
>> 0.000121000 seconds user
>> 0.002127000 seconds sys
>>
>> [root@s35lp76 perf]#
>>
>> displays output which is unexpected (and wrong):
>>
>> 2 tx_c_tend
>>
>> The test program definitely triggers only one transaction, as shown
>> in line 'TX_C_TEND: 1 expected:1'.
>
> OK, something is done twice in perf stat, but should be done once.
>
Correct
>>
>> This is caused by the following call sequence:
>>
>> pmu_lookup() scans and installs a PMU.
>> +--> pmu_aliases() parses all aliases in directory
>> .../<pmu-name>/events/* which are file names.
>> +--> pmu_aliases_parse() Read each file in directory and create
>> an new alias entry. This is done with
>> +--> perf_pmu__new_alias() and
>> +--> __perf_pmu__new_alias() which also check for
>> identical alias names.
>>
>> After pmu_aliases() returns, a complete list of event names
>> for this pmu has been created. Now function
>>
>> pmu_add_cpu_aliases() is called to add the events listed in the json
>> | files to the alias list of the cpu.
>> +--> perf_pmu__find_map() Returns a pointer to the json events.
>>
>> Now function pmu_add_cpu_aliases() scans through all events listed
>> in the JSON files for this CPU.
>
> Are these JSON files temporary in nature ?
No they are not, they are part of the perf tool, directory
[root@s35lp76 linux]# ls tools/perf/pmu-events/arch/s390/cf_z14/*
tools/perf/pmu-events/arch/s390/cf_z14/basic.json
tools/perf/pmu-events/arch/s390/cf_z14/crypto.json
tools/perf/pmu-events/arch/s390/cf_z14/extended.json
tools/perf/pmu-events/arch/s390/cf_z14/transaction.json
[root@s35lp76 linux]#
>> Each json event pmu name is compared with the current PMU being
>> built up and if they mismatch, the json event is added to the
>> current PMUs alias list.
>> To avoid duplicate entries the following comparison is done:
>>
>> if (!is_arm_pmu_core(name)) {
>> pname = pe->pmu ? pe->pmu : "cpu";
>> if (strncmp(pname, name, strlen(pname)))
>> continue;
>> }
>
> Is this the test to know whether a PMU event must be added or not ?
Correct.
>
>>
>> The culprit is the strncmp() function.
>>
>> Using current s390 PMU naming, the first PMU is 'cpum_cf'
>> and a long list of events is added, among them 'tx_c_tend'
>>
>> When the second PMU named 'cpum_cf_diag' is added, only one event
>> named 'CF_DIAG' is added by the pmu_aliases() function.
>>
>> Now function pmu_add_cpu_aliases() is invoked for PMU 'cpum_cf_diag'.
>> Since the CPUID string is the same for both PMUs, json file events
>> for PMU named 'cpum_cf' are added to the PMU 'cpm_cf_diag'
>>
>> This happens because the strncmp() actually compares:
>>> strncmp("cpum_cf", "cpum_cf_diag", 6);
>
> I fail to see how these argument values can be generated by this code:
>
> pname = pe->pmu ? pe->pmu : "cpu";
> if (strncmp(pname, name, strlen(pname)))
>
> The 3rd argument is the length of the first argument, pname.
>
> With "cpum_cf", it should be 7, not 6.
Yes, mistake on my side...
but it is the same type of error , regardless if 6 or 7 characters are
compared:
strncmp("cpmu_cf", "cpum_cf_diag", 7)
returns 0 when it should not. The device names of both PMUs are different.
>
>
>
>>
>> The first parameter is the pmu name taken from the event in
>> the json file. The second parameter is the pmu name of the PMU
>> currently being built.
>> They are different, but the length of the compare only tests the
>> common prefix and this returns 0(true) when it should return false.
>>
>
> The 6 comes from strlen(pname). In that case, it is neither the length of
> "cpum_cf" (7) or "cpum_cf_diag" (12).
Correct as said above, can not count to 7...
>
>> Now all events for PMU cpum_cf are added to the alias list for pmu
>> cpum_cf_diag.
>>
>> Later on in function parse_events_add_pmu() the event 'tx_c_end' is
>> searched in all available PMUs and found twice, adding it two
>> times to the evsel_list global variable which is the root
>> of all events. This results in a counter value of 2 instead
>> of 1.
>
> The counter value of 2 is 1 + 1 since both PMU events 'tx_c_end' that
> were added got a +1.
Correct, the transaction counter is 2 becauses it was connected to PMUs,
but only one has the counter.
>
>>
>> Output with this patch:
>>
>> [root@s35lp76 perf]# ./perf stat -e tx_c_tend \
>> -- ~/mytests/cf-tx-events 1
>> Measuring transactions
>> TX_C_TABORT_NO_SPECIAL: 0 expected:0
>> TX_C_TABORT_SPECIAL: 0 expected:0
>> TX_C_TEND: 1 expected:1
>> TX_NC_TABORT: 11 expected:11
>> TX_NC_TEND: 1 expected:1
>>
>> Performance counter stats for '/root/mytests/cf-tx-events 1':
>>
>> 1 tx_c_tend
>>
>
> OK, now that's 1, like in your expected test value:
>
> TX_C_TEND: 1 expected:1
>
>> 0.001815365 seconds time elapsed
>>
>> 0.000123000 seconds user
>> 0.001756000 seconds sys
>>
>> [root@s35lp76 perf]#
>>
>> Fixes: 292c34c10249 ("perf pmu: Fix core PMU alias list for X86 platform")
>> Signed-off-by: Thomas Richter <[email protected]>
>> Reviewed-by: Hendrik Brueckner <[email protected]>
>> Cc: Kan Liang <[email protected]>
>> Cc: <[email protected]> # 4.18+
>> ---
>> tools/perf/util/pmu.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 7799788f662f..7e49baad304d 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -773,7 +773,7 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
>>
>> if (!is_arm_pmu_core(name)) {
>> pname = pe->pmu ? pe->pmu : "cpu";
>> - if (strncmp(pname, name, strlen(pname)))
>> + if (strcmp(pname, name))
>> continue;
>> }
>>
>>
>
--
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294
On 2018-10-29 8:18 a.m., Thomas-Mich Richter wrote:
> Yes, mistake on my side...
> but it is the same type of error , regardless if 6 or 7 characters are
> compared:
>
> strncmp("cpmu_cf", "cpum_cf_diag", 7)
>
> returns 0 when it should not. The device names of both PMUs are different.
>
OK, that works then.
You want to do a full-length comparison of PMU names, instead of comparing prefixes.
Reviewed-by: Sebastien Boisvert <[email protected]>
Commit-ID: ea1fa48c055f833eb25f0c33188feecb7002ada5
Gitweb: https://git.kernel.org/tip/ea1fa48c055f833eb25f0c33188feecb7002ada5
Author: Thomas Richter <[email protected]>
AuthorDate: Tue, 23 Oct 2018 17:16:16 +0200
Committer: Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 5 Nov 2018 14:37:10 -0300
perf stat: Handle different PMU names with common prefix
On s390 the CPU Measurement Facility for counters now supports
2 PMUs named cpum_cf (CPU Measurement Facility for counters) and
cpum_cf_diag (CPU Measurement Facility for diagnostic counters)
for one and the same CPU.
Running command
[root@s35lp76 perf]# ./perf stat -e tx_c_tend \
-- ~/mytests/cf-tx-events 1
Measuring transactions
TX_C_TABORT_NO_SPECIAL: 0 expected:0
TX_C_TABORT_SPECIAL: 0 expected:0
TX_C_TEND: 1 expected:1
TX_NC_TABORT: 11 expected:11
TX_NC_TEND: 1 expected:1
Performance counter stats for '/root/mytests/cf-tx-events 1':
2 tx_c_tend
0.002120091 seconds time elapsed
0.000121000 seconds user
0.002127000 seconds sys
[root@s35lp76 perf]#
displays output which is unexpected (and wrong):
2 tx_c_tend
The test program definitely triggers only one transaction, as shown
in line 'TX_C_TEND: 1 expected:1'.
This is caused by the following call sequence:
pmu_lookup() scans and installs a PMU.
+--> pmu_aliases() parses all aliases in directory
.../<pmu-name>/events/* which are file names.
+--> pmu_aliases_parse() Read each file in directory and create
an new alias entry. This is done with
+--> perf_pmu__new_alias() and
+--> __perf_pmu__new_alias() which also check for
identical alias names.
After pmu_aliases() returns, a complete list of event names
for this pmu has been created. Now function
pmu_add_cpu_aliases() is called to add the events listed in the json
| files to the alias list of the cpu.
+--> perf_pmu__find_map() Returns a pointer to the json events.
Now function pmu_add_cpu_aliases() scans through all events listed
in the JSON files for this CPU.
Each json event pmu name is compared with the current PMU being
built up and if they mismatch, the json event is added to the
current PMUs alias list.
To avoid duplicate entries the following comparison is done:
if (!is_arm_pmu_core(name)) {
pname = pe->pmu ? pe->pmu : "cpu";
if (strncmp(pname, name, strlen(pname)))
continue;
}
The culprit is the strncmp() function.
Using current s390 PMU naming, the first PMU is 'cpum_cf'
and a long list of events is added, among them 'tx_c_tend'
When the second PMU named 'cpum_cf_diag' is added, only one event
named 'CF_DIAG' is added by the pmu_aliases() function.
Now function pmu_add_cpu_aliases() is invoked for PMU 'cpum_cf_diag'.
Since the CPUID string is the same for both PMUs, json file events
for PMU named 'cpum_cf' are added to the PMU 'cpm_cf_diag'
This happens because the strncmp() actually compares:
strncmp("cpum_cf", "cpum_cf_diag", 6);
The first parameter is the pmu name taken from the event in
the json file. The second parameter is the pmu name of the PMU
currently being built.
They are different, but the length of the compare only tests the
common prefix and this returns 0(true) when it should return false.
Now all events for PMU cpum_cf are added to the alias list for pmu
cpum_cf_diag.
Later on in function parse_events_add_pmu() the event 'tx_c_end' is
searched in all available PMUs and found twice, adding it two
times to the evsel_list global variable which is the root
of all events. This results in a counter value of 2 instead
of 1.
Output with this patch:
[root@s35lp76 perf]# ./perf stat -e tx_c_tend \
-- ~/mytests/cf-tx-events 1
Measuring transactions
TX_C_TABORT_NO_SPECIAL: 0 expected:0
TX_C_TABORT_SPECIAL: 0 expected:0
TX_C_TEND: 1 expected:1
TX_NC_TABORT: 11 expected:11
TX_NC_TEND: 1 expected:1
Performance counter stats for '/root/mytests/cf-tx-events 1':
1 tx_c_tend
0.001815365 seconds time elapsed
0.000123000 seconds user
0.001756000 seconds sys
[root@s35lp76 perf]#
Signed-off-by: Thomas Richter <[email protected]>
Reviewed-by: Hendrik Brueckner <[email protected]>
Reviewed-by: Sebastien Boisvert <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: [email protected]
Fixes: 292c34c10249 ("perf pmu: Fix core PMU alias list for X86 platform")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/util/pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 7799788f662f..7e49baad304d 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -773,7 +773,7 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
if (!is_arm_pmu_core(name)) {
pname = pe->pmu ? pe->pmu : "cpu";
- if (strncmp(pname, name, strlen(pname)))
+ if (strcmp(pname, name))
continue;
}