Re: [PATCH v2 0/7] perf arm-spe: Enable timestamp

[Adrian Hunter]

On 7/04/21 4:15 pm, Leo Yan wrote:
> Hi Al,
> 
> On Tue, Apr 06, 2021 at 09:38:32AM +0000, Al Grant wrote:
> 
> [...]
> 
>>> This patch set is to enable timestamp for Arm SPE trace.  It reads out TSC
>>> parameters from mmap page and stores into auxtrace info structure;
>>
>> Why not synthesize a PERF_RECORD_TIME_CONV - isn't that specifically to
>> capture the TSC parameters from the mmap page? If a generic mechanism
>> exists it would be better to use it, otherwise we'll have to do this again for
>> future trace formats.
> 
> Good point!  Actually "perf record" tool has synthesized event
> PERF_RECORD_TIME_CONV.  This patch series is studying the
> implementation from Intel-PT, so the question is why the existed
> implementations (like Intel-PT, Intel-BTS) don't directly use
> PERF_RECORD_TIME_CONV for retriving TSC parameters.

PERF_RECORD_TIME_CONV was added later because the TSC information is
needed by jitdump.