linux-kernel - v4: Re: [PATCH v7 00/15] coresight: Add new API to allocate trace source ID values

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Message-ID: <e3df35fe-a00d-69ec-32ee-53c949909cab@arm.com>
Date:   Mon, 20 Feb 2023 16:24:39 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
        linux-perf-users@...r.kernel.org, leo.yan@...aro.org,
        quic_jinlmao@...cinc.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Mike Leach <mike.leach@...aro.org>,
        James Clark <james.clark@....com>
Subject: v4: Re: [PATCH v7 00/15] coresight: Add new API to allocate trace
 source ID values

Arnaldo

Gentle ping


On 31/01/2023 11:49, Suzuki K Poulose wrote:
> Hi Arnaldo
> 
> On 24/01/2023 11:36, Suzuki K Poulose wrote:
>> Hi Arnaldo
>>
>> Gentle ping.
>>
>> On 19/01/2023 12:00, Suzuki K Poulose wrote:
>>> Hi Arnaldo,
>>>
>>> On 16/01/2023 12:49, Mike Leach wrote:
>>>> The current method for allocating trace source ID values to sources is
>>>> to use a fixed algorithm for CPU based sources of (cpu_num * 2 + 0x10).
>>>> The STM is allocated ID 0x1.
>>>>
>>>> This fixed algorithm is used in both the CoreSight driver code, and by
>>>> perf when writing the trace metadata in the AUXTRACE_INFO record.
>>>>
>>>> The method needs replacing as currently:-
>>>> 1. It is inefficient in using available IDs.
>>>> 2. Does not scale to larger systems with many cores and the algorithm
>>>> has no limits so will generate invalid trace IDs for cpu number > 44.
>>>>
>>>> Additionally requirements to allocate additional system IDs on some
>>>> systems have been seen.
>>>>
>>>> This patch set  introduces an API that allows the allocation of 
>>>> trace IDs
>>>> in a dynamic manner.
>>>>
>>>> Architecturally reserved IDs are never allocated, and the system is
>>>> limited to allocating only valid IDs.
>>>>
>>>> Each of the current trace sources ETM3.x, ETM4.x and STM is updated 
>>>> to use
>>>> the new API.
>>>>
>>>> For the ETMx.x devices IDs are allocated on certain events
>>>> a) When using sysfs, an ID will be allocated on hardware enable, or 
>>>> a read of
>>>> sysfs TRCTRACEID register and freed when the sysfs reset is written.
>>>>
>>>> b) When using perf, ID is allocated on during setup AUX event, and 
>>>> freed on
>>>> event free. IDs are communicated using the AUX_OUTPUT_HW_ID packet.
>>>> The ID allocator is notified when perf sessions start and stop
>>>> so CPU based IDs are kept constant throughout any perf session.
>>>>
>>>>
>>>> Note: This patchset breaks some backward compatibility for perf 
>>>> record and
>>>> perf report.
>>>>
>>>> The version of the AUXTRACE_INFO has been updated to reflect the 
>>>> fact that
>>>> the trace source IDs are generated differently. This will
>>>> mean older versions of perf report cannot decode the newer file.
>>>>
>>>> Appies to coresight/next
>>>>
>>
>> ...
>>
>>>> Mike Leach (15):
>>>>    coresight: trace-id: Add API to dynamically assign Trace ID values
>>>>    coresight: Remove obsolete Trace ID unniqueness checks
>>>>    coresight: perf: traceid: Add perf ID allocation and notifiers
>>>>    coresight: stm: Update STM driver to use Trace ID API
>>>>    coresight: etm4x: Update ETM4 driver to use Trace ID API
>>>>    coresight: etm3x: Update ETM3 driver to use Trace ID API
>>>>    coresight: etmX.X: stm: Remove trace_id() callback
>>>>    coresight: trace id: Remove legacy get trace ID function.
>>>>    perf: cs-etm: Move mapping of Trace ID and cpu into helper function
>>>>    perf: cs-etm: Update record event to use new Trace ID protocol
>>>>    kernel: events: Export perf_report_aux_output_id()
>>>>    perf: cs-etm: Handle PERF_RECORD_AUX_OUTPUT_HW_ID packet
>>>>    coresight: events: PERF_RECORD_AUX_OUTPUT_HW_ID used for Trace ID
>>>>    coresight: trace-id: Add debug & test macros to Trace ID allocation
>>>>    coresight: etm3x: docs: Alter sysfs documentation for trace id 
>>>> updates
>>>
>>> I have pushed the kernel patches on this series to coresight tree 
>>> next[0].
>>>
>>> I will be sending them out to Greg for v6.3. Please could you queue the
>>> perf tool changes in the series ? i.e., Patches 9,10 and 12.
>>>
>>>
>>> [0] 
>>> https://git.kernel.org/pub/scm/linux/kernel/git/coresight/linux.git/log/?h=next
>>>
>>
>> Please could you pick up the perf tool changes above ?
> 
> Please could you confirm if you are able to queue the perf tool changes 
> ? Or would you like me route it via coresight tree ?
> 
> Kind regards
> Suzuki
> 


Suzuki