Bug#91815: Patch to add memusage and memusagestat

[Helmut Grohne <helmut@subdivi.de>]

Hi Stephen,

Thank you for not dropping the ball after my initial "it's not that
easy" reply.

On Sat, May 09, 2020 at 10:53:10AM +0200, Stephen Kitt wrote:
> There’s another part of the transition which bothers me: if we add memusage
> to a package which is depended upon (albeit temporarily) by libc-dev-bin, it
> becomes part of build-essential, and adding memusage means adding libgd3,
> libfontconfig1, libfreetype6, etc. to all builds...
> 
> It occurred to me that there is however a way to add memusage while
> transitioning cleanly, over a few years. It seems to me that the binaries in
> libc-dev-bin can be split into two categories: binaries that are expected as
> build tools (gencat and rpcgen), and binaries that are useful as tools for
> understanding programs but not building them (memusage, memusagestat, mtrace,
> sotruss, sprof). How about the following?
> 
> * We add a new package, say libc-devtools, containing the second type of
>   tools (mtrace, sotruss, sprof). For transition purposes, libc-dev-bin
>   depends on that in Bullseye.
> * We add another package, memusage, containing memusage and memusagestat.
>   That’s the package which ends up with all the annoying extra dependencies,
>   but nothing depends on it.
> * In Bookworm, libc-dev-bin can drop the dependency on libc-devtools, and we
>   can merge memusage into libc-devtools.
> 
> Does that make sense?

All of what you write here makes very much sense to me and the
trade-offs seem good to me. What you propose will result in making the
bootstrapping/profile stuff simpler/better. That said, I am not a glibc
maintainer. I don't see the full picture.

I have two minor remarks:
 * Should libc-devtools maybe recommend memusage already?
 * We cannot simply have libc-devtools absorb memusage in bookworm.
   Doing so would break upgrades when someone has memusage, but not
   libc-devtools installed. Therefore memusage likely needs to be a
   transitional dummy package in bookworm and can only be removed one
   release later. I'm wondering whether this could be avoided if we had
   memusage depend on libc-devtools.

Neither of these touch the core of your thoughts.

I'm happy to review patches to make this happen. Please continue to Cc
me if you want my review.

Helmut