Re: [PATCH v2 0/9] Trace2 stopwatch timers and global counters

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Dec 29, 2021, 01:54 UTC
Message-ID: <211229.86ee5wgnug.gmgdl@evledraar.gmail.com>
In-Reply-To: <pull.1099.v2.git.1640720202.gitgitgadget@gmail.com>

On Tue, Dec 28 2021, Jeff Hostetler via GitGitGadget wrote:

I left some other comments on the series inline, just on the notes in the CL:

>  * Ævar proposed a large refactor of the "_perf" target to have a "fmt()"
>    varargs function to reduce the amount of copy-n-pasted code in many of
>    the "fn" event handlers. This looks like a good change based on the
>    mockup but is a large refactor.

FWIW what I meant with [1] was not that this series needed to take the detour of refactoring trace2/tr2_tgt_perf.c to use such a helper, but that for the function additions in this series it might make sense to introduce one and use it for the new functions.

For this series I think it's probably not worth it, so I'm fine with leaving this for some other time. Just pointing out that rather than your reading of:

 1. We have some refactorable verbosity
 2. Refactor all callers
 3. Change existing code to use that refactoring
 4. Add new code to use the refactoring

It's also perfectly fine to do just:

 1. We have some refactorable verbosity
 2. Introduce a less verbose
 3. Add new code to use the helper

And leave the "refactor all callers" for some other time.

Anyway, I think for the two callers just leaving it entirely for this series is the right thing to do. It was more of a "hrm, that's some odd and avoidable verbosity..." comment on me read-through of v1.

1. https://lore.kernel.org/git/211220.86czlrurm6.gmgdl@evledraar.gmail.com/

>  * Ævar proposed a new rationale for when/why we change the "_event" version
>    number. That text can be added to the design document independently.

Hrm, no. In [1] I linked to some earlier musings of mine about what we should do about the TR2_EVENT_VERSION (mainly as an FYI since you added it, but hadn't commented on that post).

But my main comment there was that the series wasn't progressing as atomic changes. I.e. we promise to change the TR2_EVENT_VERSION version every time we change the event format, but v1 first changed the format and bumped the version, then made some more changes.

I think that's probably fine per-se within a git release cycle, but it might be a symtom of commits that could be split up to be more atomic (I don't know, didn't look in detail).

However, in this v2 of the series the TR2_EVENT_VERSION bump is entirely gone.

Maybe that means that you so vehemently agree with my proposal in [1] it that you'd like to start taking that view for trace2 changes right away :-)

For me it's fine either way, I think TR2_EVENT_VERSION probably isn't that important.

But if that's the case it should probably be called out more explictly in the CL/commit. I.e. even if our "policy" (such as it is) about TR2_EVENT_VERSION currently says X we're going to start doing Y here intentionally.

And in that case I should probably turn that suggestion in [1] into a an actual PATCH sooner than later...

1. https://lore.kernel.org/git/211220.86czlrurm6.gmgdl@evledraar.gmail.com/