Re: [PATCH 2/9] perf/core: Add PERF_SAMPLE_CGROUP feature

[Namhyung Kim]

Hello Song,

On Thu, Sep 19, 2019 at 3:43 PM Song Liu <liu.song.a23@xxxxxxxxx> wrote:

> Sharing some offline discussions with Tejun.
>
> ino in current kernfs is not a good unique ID for cgroup, because it doesn't
> increase monotonically. So we need to improve kernfs.
>
> For 64-bit, we can make the ino monotonic, and use it as the ID.
> For 32-bit, we need to make the ino monotonic. and use <ino> and <gen>
> as the 64-bit ID.

Thanks for the sharing information!  For 32-bit, while the ino itself is not
monotonic, gen << 32 + ino is monotonic right?  I think we can use the
same logic of kernfs id allocation, but not sure what the problem Tejun
mentioned before is.

Thanks,
Namhyung