Re: [PATCH v3 13/35] lib: add allocation tagging support for memory allocation profiling

Kent Overstreet
2024-02-16T01:01:00Z

On Thu, Feb 15, 2024 at 04:54:38PM -0800, Andrew Morton wrote:
> On Mon, 12 Feb 2024 13:38:59 -0800 Suren Baghdasaryan <surenb@google.com> wrote:
>
> > +Example output.
> > +
> > +::
> > +
> > + > cat /proc/allocinfo
> > +
> > + 153MiB mm/slub.c:1826 module:slub func:alloc_slab_page
> > + 6.08MiB mm/slab_common.c:950 module:slab_common func:_kmalloc_order
> > + 5.09MiB mm/memcontrol.c:2814 module:memcontrol func:alloc_slab_obj_exts
> > + 4.54MiB mm/page_alloc.c:5777 module:page_alloc func:alloc_pages_exact
> > + 1.32MiB include/asm-generic/pgalloc.h:63 module:pgtable func:__pte_alloc_one
>
> I don't really like the fancy MiB stuff. Wouldn't it be better to just
> present the amount of memory in plain old bytes, so people can use sort
> -n on it?

They can use sort -h on it; the string_get_size() patch was specifically
so that we could make the output compatible with sort -h

> And it's easier to tell big-from-small at a glance because
> big has more digits.
>
> Also, the first thing any sort of downstream processing of this data is
> going to have to do is to convert the fancified output back into
> plain-old-bytes. So why not just emit plain-old-bytes?
>
> If someone wants the fancy output (and nobody does) then that can be
> done in userspace.

I like simpler, more discoverable tools; e.g. we've got a bunch of
interesting stuff in scripts/ but it doesn't get used nearly as much -
not as accessible as cat'ing a file, definitely not going to be
installed by default.

I'm just optimizing for the most common use case. I doubt there's going
to be nearly as much consumption by tools, and I'm ok with making them
do the conversion back to bytes if they really need it.