About using PEBS from the user space

About using PEBS from the user space

[Harald Servat]

Dear list,

   I'd like to use the perf library to access PEBS so as to collect 
referenced memory addresses from the user space. I think I've 
successfully setup the perf structures (struct perf_event_attr) to 
configure the performance counters, but I don't see what should I do to 
access to the captured memory addresses. I've seen that within 
arch/x86/kernel/cpu/perf_event_intel_ds.c there are the routines 
alloc_pebs_buffer, alloc_ds_buffer which seems to allocate and setup the 
necessary buffers using kmalloc_node calls. Question is, how can 
replicate this from the user space? And how we should connect these 
buffers to the PEBS infrastructure using perf calls?

Thank you very much in advance.

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Re: About using PEBS from the user space

[Vince Weaver]

On Mon, 4 May 2015, Harald Servat wrote:

> Dear list,
> 
>   I'd like to use the perf library to access PEBS so as to collect referenced
> memory addresses from the user space. I think I've successfully setup the perf
> structures (struct perf_event_attr) to configure the performance counters, but
> I don't see what should I do to access to the captured memory addresses. I've
> seen that within arch/x86/kernel/cpu/perf_event_intel_ds.c there are the
> routines alloc_pebs_buffer, alloc_ds_buffer which seems to allocate and setup
> the necessary buffers using kmalloc_node calls. Question is, how can replicate
> this from the user space? And how we should connect these buffers to the PEBS
> infrastructure using perf calls?

You can try looking at the example code in my perf_event_tests code.
	https://github.com/deater/perf_event_tests

The stuff you are looking for is probably covered in the
	test/record_sample/samples_data_src
	test/record_sample/sample_weight
and especially the
	test/record_sample/sample_regs_intr
tests, although that last one requires a fairly recent kernel to work.

Vince

Re: About using PEBS from the user space

[Harald Servat]

On 04/05/15 00:19, Vince Weaver wrote:
> On Mon, 4 May 2015, Harald Servat wrote:
>
>> Dear list,
>>
>>    I'd like to use the perf library to access PEBS so as to collect referenced
>> memory addresses from the user space. I think I've successfully setup the perf
>> structures (struct perf_event_attr) to configure the performance counters, but
>> I don't see what should I do to access to the captured memory addresses. I've
>> seen that within arch/x86/kernel/cpu/perf_event_intel_ds.c there are the
>> routines alloc_pebs_buffer, alloc_ds_buffer which seems to allocate and setup
>> the necessary buffers using kmalloc_node calls. Question is, how can replicate
>> this from the user space? And how we should connect these buffers to the PEBS
>> infrastructure using perf calls?
>
> You can try looking at the example code in my perf_event_tests code.
> 	https://github.com/deater/perf_event_tests
>
> The stuff you are looking for is probably covered in the
> 	test/record_sample/samples_data_src
> 	test/record_sample/sample_weight
> and especially the
> 	test/record_sample/sample_regs_intr
> tests, although that last one requires a fairly recent kernel to work.
>
> Vince

   Thank you very much for these pointers Vince. I'll take a look at them!

Best regards.



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Re: About using PEBS from the user space

[Harald Servat]

[-- Attachment #1: Type: text/plain, Size: 3669 bytes --]

On 04/05/15 00:19, Vince Weaver wrote:
> On Mon, 4 May 2015, Harald Servat wrote:
>
>> Dear list,
>>
>>    I'd like to use the perf library to access PEBS so as to collect referenced
>> memory addresses from the user space. I think I've successfully setup the perf
>> structures (struct perf_event_attr) to configure the performance counters, but
>> I don't see what should I do to access to the captured memory addresses. I've
>> seen that within arch/x86/kernel/cpu/perf_event_intel_ds.c there are the
>> routines alloc_pebs_buffer, alloc_ds_buffer which seems to allocate and setup
>> the necessary buffers using kmalloc_node calls. Question is, how can replicate
>> this from the user space? And how we should connect these buffers to the PEBS
>> infrastructure using perf calls?
>
> You can try looking at the example code in my perf_event_tests code.
> 	https://github.com/deater/perf_event_tests
>
> The stuff you are looking for is probably covered in the
> 	test/record_sample/samples_data_src
> 	test/record_sample/sample_weight
> and especially the
> 	test/record_sample/sample_regs_intr
> tests, although that last one requires a fairly recent kernel to work.
>
> Vince

   Vince,

   that is really interesting work, thank you! However, for some reason 
the PEBS collected address is never shown (and maybe not captured) 
according to the following partial output

PERF_RECORD_SAMPLE [c001], MISC=16386 
(PERF_RECORD_MISC_USER,PERF_RECORD_MISC_EXACT_IP ), Size=32
	PERF_SAMPLE_IP, IP: 404510
	PERF_SAMPLE_WEIGHT, Weight: 30
	PERF_SAMPLE_DATA_SRC, Raw: 68100242
		Load Hit Line fill buffer No snoop Hit Level 1 TLB Level 2 TLB
PERF_RECORD_SAMPLE [c001], MISC=16386 
(PERF_RECORD_MISC_USER,PERF_RECORD_MISC_EXACT_IP ), Size=32
	PERF_SAMPLE_IP, IP: 404524
	PERF_SAMPLE_WEIGHT, Weight: 76
	PERF_SAMPLE_DATA_SRC, Raw: 68100442
		Load Hit L2 cache No snoop Hit Level 1 TLB Level 2 TLB
PERF_RECORD_SAMPLE [c001], MISC=16386 
(PERF_RECORD_MISC_USER,PERF_RECORD_MISC_EXACT_IP ), Size=32
	PERF_SAMPLE_IP, IP: 404524
	PERF_SAMPLE_WEIGHT, Weight: 77
	PERF_SAMPLE_DATA_SRC, Raw: 68100842
		Load Hit L3 cache No snoop Hit Level 1 TLB Level 2 TLB

   I've looked into your code in order to compare it with the perf tool 
and it looks like you support it in the code in the following lines of 
lib/parse_record.c, so it looks that sample_type is not tagged with 
PERF_SAMPLE_ADDR bit.

511             if (sample_type & PERF_SAMPLE_ADDR) {
512                 long long addr;
513                 memcpy(&addr,&data[offset],sizeof(long long));
514                 if (!quiet) printf("\tPERF_SAMPLE_ADDR, addr: 
%llx\n",addr);
515                 offset+=8;
516             }

   I tweaked a bit the perf dump application so that it prints the 
sample_type and it always shows c10f whereas your binary prints c001. If 
I simply go to one of the tests (say sample_data_src.c) and force 
pe.sample = 0xc10f then it works (printing additional data). So, would 
the following change make sense into your code to emit the sampled address?

Best regards.



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[-- Attachment #2: sample_data_src.c.patch --]
[-- Type: text/x-patch, Size: 531 bytes --]

diff --git a/tests/record_sample/sample_data_src.c b/tests/record_sample/sample_data_src.c
index 1c3d260..35c7e81 100644
--- a/tests/record_sample/sample_data_src.c
+++ b/tests/record_sample/sample_data_src.c
@@ -113,7 +113,7 @@ int main(int argc, char **argv) {
         pe.size=sizeof(struct perf_event_attr);
         pe.sample_period=SAMPLE_FREQUENCY;
         pe.sample_type=PERF_SAMPLE_IP | PERF_SAMPLE_WEIGHT |
-			PERF_SAMPLE_DATA_SRC;
+			PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_ADDR ;
 
 	global_sample_type=pe.sample_type;
 

Re: About using PEBS from the user space

[Harald Servat]

On 04/05/15 00:19, Vince Weaver wrote:
> On Mon, 4 May 2015, Harald Servat wrote:
>
>> Dear list,
>>
>>    I'd like to use the perf library to access PEBS so as to collect referenced
>> memory addresses from the user space. I think I've successfully setup the perf
>> structures (struct perf_event_attr) to configure the performance counters, but
>> I don't see what should I do to access to the captured memory addresses. I've
>> seen that within arch/x86/kernel/cpu/perf_event_intel_ds.c there are the
>> routines alloc_pebs_buffer, alloc_ds_buffer which seems to allocate and setup
>> the necessary buffers using kmalloc_node calls. Question is, how can replicate
>> this from the user space? And how we should connect these buffers to the PEBS
>> infrastructure using perf calls?
>
> You can try looking at the example code in my perf_event_tests code.
> 	https://github.com/deater/perf_event_tests
>
> The stuff you are looking for is probably covered in the
> 	test/record_sample/samples_data_src
> 	test/record_sample/sample_weight
> and especially the
> 	test/record_sample/sample_regs_intr
> tests, although that last one requires a fairly recent kernel to work.
>
> Vince

Hello,

   is there a way to setup PEBS to collect information from loads that 
take at least X cycles to complete using MSR_PEBS_LD_LAT_THRESHOLD 
through this approach?

Thank you!

WARNING / LEGAL TEXT: This message is intended only for the use of the
individual or entity to which it is addressed and may contain
information which is privileged, confidential, proprietary, or exempt
from disclosure under applicable law. If you are not the intended
recipient or the person responsible for delivering the message to the
intended recipient, you are strictly prohibited from disclosing,
distributing, copying, or in any way using this message. If you have
received this communication in error, please notify the sender and
destroy and delete any copies you may have received.

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Re: About using PEBS from the user space

[Manuel Selva]

Hello Harald,

Setting the  config1 field of the perf_event_attr field (as done by the 
perf mem record tool) to X will instruct the PMU to only sample loads 
with latency higher than X. Is it what you are looking for ?

----
Manu

On 06/25/2015 06:00 PM, Harald Servat wrote:
> On 04/05/15 00:19, Vince Weaver wrote:
>> On Mon, 4 May 2015, Harald Servat wrote:
>>
>>> Dear list,
>>>
>>>    I'd like to use the perf library to access PEBS so as to collect
>>> referenced
>>> memory addresses from the user space. I think I've successfully setup
>>> the perf
>>> structures (struct perf_event_attr) to configure the performance
>>> counters, but
>>> I don't see what should I do to access to the captured memory
>>> addresses. I've
>>> seen that within arch/x86/kernel/cpu/perf_event_intel_ds.c there are the
>>> routines alloc_pebs_buffer, alloc_ds_buffer which seems to allocate
>>> and setup
>>> the necessary buffers using kmalloc_node calls. Question is, how can
>>> replicate
>>> this from the user space? And how we should connect these buffers to
>>> the PEBS
>>> infrastructure using perf calls?
>>
>> You can try looking at the example code in my perf_event_tests code.
>>     https://github.com/deater/perf_event_tests
>>
>> The stuff you are looking for is probably covered in the
>>     test/record_sample/samples_data_src
>>     test/record_sample/sample_weight
>> and especially the
>>     test/record_sample/sample_regs_intr
>> tests, although that last one requires a fairly recent kernel to work.
>>
>> Vince
>
> Hello,
>
>    is there a way to setup PEBS to collect information from loads that
> take at least X cycles to complete using MSR_PEBS_LD_LAT_THRESHOLD
> through this approach?
>
> Thank you!
>
> WARNING / LEGAL TEXT: This message is intended only for the use of the
> individual or entity to which it is addressed and may contain
> information which is privileged, confidential, proprietary, or exempt
> from disclosure under applicable law. If you are not the intended
> recipient or the person responsible for delivering the message to the
> intended recipient, you are strictly prohibited from disclosing,
> distributing, copying, or in any way using this message. If you have
> received this communication in error, please notify the sender and
> destroy and delete any copies you may have received.
>
> http://www.bsc.es/disclaimer
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>
>

Re: About using PEBS from the user space

[Harald Servat]

Ah! Great, thank you Manuel!!

On 25/06/15 21:06, Manuel Selva wrote:
> Hello Harald,
>
> Setting the  config1 field of the perf_event_attr field (as done by the
> perf mem record tool) to X will instruct the PMU to only sample loads
> with latency higher than X. Is it what you are looking for ?
>
> ----
> Manu
>
> On 06/25/2015 06:00 PM, Harald Servat wrote:
>> On 04/05/15 00:19, Vince Weaver wrote:
>>> On Mon, 4 May 2015, Harald Servat wrote:
>>>
>>>> Dear list,
>>>>
>>>>    I'd like to use the perf library to access PEBS so as to collect
>>>> referenced
>>>> memory addresses from the user space. I think I've successfully setup
>>>> the perf
>>>> structures (struct perf_event_attr) to configure the performance
>>>> counters, but
>>>> I don't see what should I do to access to the captured memory
>>>> addresses. I've
>>>> seen that within arch/x86/kernel/cpu/perf_event_intel_ds.c there are
>>>> the
>>>> routines alloc_pebs_buffer, alloc_ds_buffer which seems to allocate
>>>> and setup
>>>> the necessary buffers using kmalloc_node calls. Question is, how can
>>>> replicate
>>>> this from the user space? And how we should connect these buffers to
>>>> the PEBS
>>>> infrastructure using perf calls?
>>>
>>> You can try looking at the example code in my perf_event_tests code.
>>>     https://github.com/deater/perf_event_tests
>>>
>>> The stuff you are looking for is probably covered in the
>>>     test/record_sample/samples_data_src
>>>     test/record_sample/sample_weight
>>> and especially the
>>>     test/record_sample/sample_regs_intr
>>> tests, although that last one requires a fairly recent kernel to work.
>>>
>>> Vince
>>
>> Hello,
>>
>>    is there a way to setup PEBS to collect information from loads that
>> take at least X cycles to complete using MSR_PEBS_LD_LAT_THRESHOLD
>> through this approach?
>>
>> Thank you!
>>
>> WARNING / LEGAL TEXT: This message is intended only for the use of the
>> individual or entity to which it is addressed and may contain
>> information which is privileged, confidential, proprietary, or exempt
>> from disclosure under applicable law. If you are not the intended
>> recipient or the person responsible for delivering the message to the
>> intended recipient, you are strictly prohibited from disclosing,
>> distributing, copying, or in any way using this message. If you have
>> received this communication in error, please notify the sender and
>> destroy and delete any copies you may have received.
>>
>> http://www.bsc.es/disclaimer
>> --
>> To unsubscribe from this list: send the line "unsubscribe
>> linux-perf-users" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>>


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