Re: [PATCH v4 0/2] Make sysFS functional on topologies with per core sink

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 11/12/20 8:57 AM, Linu Cherian wrote:
> Hi Suzuki,
> 
> On Tue, Nov 10, 2020 at 8:27 PM Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>>
>> Hi Linu
>>
>> On 11/10/20 12:57 PM, Linu Cherian wrote:
>>> Hi Suzuki,
>>>
>> ...
>>

....

>>> # ./perf report
>>> 0x368 [0x50]: failed to process type: 1 [Cannot allocate memory]
>>> Error:
>>> failed to process sample
>>
>> I have no clue about it. Are you able to run it under GDB ? (Looks like
>> you have built the perf, so if you have sources, it may be a good idea
>> to run under the GDB and figure out where that error is coming from).
>>
> 
> Yeah gdb helped figuring out the issue.
> The issue is in the opencsd, where it doesn't seem to support multiple streams
> when the formatter is not enabled. .
> Note:Our Silicon has formatter disabled and we already had changes in perf tool
> to take care of the formatter status.
> 
> The below hack helped.
> 
> diff --git a/decoder/source/ocsd_dcd_tree.cpp b/decoder/source/ocsd_dcd_tree.cpp
> index be15e36..0210dec 100644
> --- a/decoder/source/ocsd_dcd_tree.cpp
> +++ b/decoder/source/ocsd_dcd_tree.cpp
> @@ -401,7 +401,7 @@ ocsd_err_t DecodeTree::createDecoder(const
> std::string &decoderName, const int c
>       int crtFlags = createFlags;
> 
>       uint8_t CSID = 0;   // default for single stream decoder (no
> deformatter) - we ignore the ID
> -    if(usingFormatter())
> +    //if(usingFormatter())
>       {
>           CSID = pConfig->getTraceID();
>           crtFlags |= OCSD_CREATE_FLG_INST_ID;
> 
> 
> Not sure if this is the right fix though.

That may work for you, but would break the existing platforms
and the drivers which enable formatting by default.
We need a way to address this in the perf side. This would be
needed for the ETE/TRBE trace scenario as well, where
the formatting is not supported by TRBE.

> 
> This is how i tested,
> 
> 1. # taskset 0x2 ./perf record -e cs_etm//u -F 10 --per-thread ping -c
> 30 127.0.0.1
> 
> 2. # Ctrl-Z // Put the process in background
> 
> 3. # taskset -p 0x4 <pid of ping process> // Move the ping process to core 2
> 
> 4. # fg // Get the process to foreground
> 
> 5. ./perf report
> snip ...
> 
> # Samples: 66K of event 'branches:uH'
> # Event count (approx.): 66953
> #
> # Children      Self  Command  Shared Object          Symbol
> # ........  ........  .......  .....................
> ........................................
> #
>      15.94%    15.94%  ping     ld-2.31.so             [.] _dl_lookup_symbol_x
>      14.93%    14.93%  ping     ld-2.31.so             [.] do_lookup_x
>      10.68%    10.68%  ping     libc-2.31.so           [.] _dl_addr
>       9.87%     9.87%  ping     ld-2.31.so             [.] _dl_relocate_object
>       6.75%     6.75%  ping     ld-2.31.so             [.] strcmp
>       3.62%     3.62%  ping     ld-2.31.so             [.] check_match
>       2.72%     2.72%  ping     libc-2.31.so           [.] __vfprintf_internal
>       1.90%     1.90%  ping     libc-2.31.so           [.] _int_malloc
>       1.29%     1.29%  ping     libc-2.31.so           [.] getenv
>       1.28%     1.28%  ping     libc-2.31.so           [.] strcmp
>       1.17%     1.17%  ping     libc-2.31.so           [.]
> _IO_file_xsputn@@GLIBC_2.17
>       1.16%     1.16%  ping     ld-2.31.so             [.] _dl_name_match_p
> 
> snip ...
> 
> Also i could verify using prints in the tmc-etr-driver that the trace
> buffer gets reused across cores
> as well.

Cool ! So please could you test the newer version of this patch (not functionally
different, but slightly modified code) and add a Tested-by if you are happy
with it ?

https://lore.kernel.org/linux-arm-kernel/1605012309-24812-3-git-send-email-anshuman.khandual@arm.com/

Cheers
Suzuki



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