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

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Message-ID: <6a71acac-c478-6e5d-3165-4ba9526614db@arm.com>
Date:   Mon, 27 Feb 2023 10:26:28 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mike Leach <mike.leach@...aro.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: Re: v4: Re: [PATCH v7 00/15] coresight: Add new API to allocate trace
 source ID values

Mike,

Please could you send all the perf tool related patches as a seperate
series, with all the tags to Arnaldo directly at -rc1.

Please add a cover letter explaining that the kernel changes are
available upstream.

Kind regards
Suzuki

On 20/02/2023 16:24, Suzuki K Poulose wrote:
> 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
>