Re: [LSF/MM/BPF TOPIC] Memory profiling using code tagging

[Kent Overstreet <kent.overstreet@linux.dev>]

On Tue, Mar 28, 2023 at 06:28:21PM +0200, Vlastimil Babka wrote:
> On 2/22/23 20:31, Suren Baghdasaryan wrote:
> > We would like to continue the discussion about code tagging use for
> > memory allocation profiling. The code tagging framework [1] and its
> > applications were posted as an RFC [2] and discussed at LPC 2022. It
> > has many applications proposed in the RFC but we would like to focus
> > on its application for memory profiling. It can be used as a
> > low-overhead solution to track memory leaks, rank memory consumers by
> > the amount of memory they use, identify memory allocation hot paths
> > and possible other use cases.
> > Kent Overstreet and I worked on simplifying the solution, minimizing
> > the overhead and implementing features requested during RFC review.
> 
> IIRC one large objection was the use of page_ext, I don't recall if you
> found another solution to that?

Hasn't been addressed yet, but we were just talking about moving the
codetag pointer from page_ext to page last night for memory overhead
reasons.

The disadvantage then is that the memory overhead doesn't go down if you
disable memory allocation profiling at boot time...

But perhaps the performance overhead is low enough now that this is not
something we expect to be doing as much?

Choices, choices...