[dpdk-dev] [EXT] Re: [PATCH 1/1] eal: increase TRACE CTF SIZE to recommended size

[David Marchand]

On Tue, Oct 6, 2020 at 11:22 AM Sunil Kumar Kori <skori at marvell.com> wrote:
> >On Mon, Oct 5, 2020 at 10:16 PM Timothy McDaniel
> ><timothy.mcdaniel at intel.com> wrote:
> >>
> >> Increase TRACE_CTF_FIELD_SIZE to 448, the recommended size.
> >
> >Repeating the same sentence in the title and the commitlog does not give
> >much info.
> >
> >Plus, what is this "recommendation"?
> When analyzed this issue, only one more byte was needed to fix this issue but in future similar issue can occur again.
> So increasing this value by 64 bytes which actually equals to a cache line. That’s why we have suggested this size.

384 is aligned to both 64 and 128 bytes cache lines.
448 is only aligned to 64 bytes.

Should we care about 128 bytes cache lines systems?

>
> >
> >
> >> Fixes "CTF field is too long" error when running with trace enabled.
> >
> >Ok, you hit this limit, but it would help to get some context here.
> >Looking at this patch in the future, we won't know why it was necessary.

How about following commitlog:

"""
trace: increase trace point buffer size

The current buffer size is not big enough to accomodate traces for new
additions in the eventdev subsystem.
Increase this buffer size by XXX for reason YYY.
"""


-- 
David Marchand