Re: [PATCH 02/26] perf: Introduce mmap3 version of mmap event

peterz
2020-09-14T09:08:40Z

On Sun, Sep 13, 2020 at 11:41:00PM -0700, Stephane Eranian wrote:
> On Sun, Sep 13, 2020 at 2:03 PM Jiri Olsa <jolsa@kernel.org> wrote:
> what happens if I set mmap3 and mmap2?
>
> I think using mmap3 for every mmap may be overkill as you add useless
> 20 bytes to an mmap record.
> I am not sure if your code handles the case where mmap3 is not needed
> because there is no buildid, e.g, anonymous memory.
> It seems to me you've written the patch in such a way that if the user
> tool supports mmap3, then it supersedes mmap2, and thus
> you need all the fields of mmap2. But if could be more interesting to
> return either MMAP2 or MMAP3 depending on tool support
> and type of mmap, that would certainly save 20 bytes on any anon mmap.
> But maybe that logic is already in your patch and I missed it.

That, and what if you don't want any of that buildid nonsense at all? I
always kill that because it makes perf pointlessly slow and has
absolutely no upsides for me.