Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback

German Gomez
2021-10-11T15:55:48Z

Hi Leo,

On 06/10/2021 10:51, Leo Yan wrote:
> On Wed, Oct 06, 2021 at 10:35:20AM +0100, German Gomez wrote:
>
> [...]
>
>>> So simply say, I think the head pointer monotonically increasing is
>>> the right thing to do in Arm SPE driver.
>> I will talk to James about how we can proceed on this.
> Thanks!

I took this offline with James and, though it looks possible to patch
the SPE driver to have a monotonically increasing head pointer in order
to simplify the handling in the perf tool, it could be a breaking change
for users of the perf_event_open syscall that currently rely on the way
it works now.

An alternative way we considered to simplify the patch is to change the
logic inside the find_snapshot callback so that it records the entire
contents of the aux buffer every time.

What do you think?

Many thanks,
German