Re: [RFC PATCH 00/30] Code tagging framework and applications

Kent Overstreet
2022-09-01T14:24:46Z

On Thu, Sep 01, 2022 at 10:05:03AM +0200, David Hildenbrand wrote:
> On 31.08.22 21:01, Kent Overstreet wrote:
> > On Wed, Aug 31, 2022 at 12:47:32PM +0200, Michal Hocko wrote:
> >> On Wed 31-08-22 11:19:48, Mel Gorman wrote:
> >>> Whatever asking for an explanation as to why equivalent functionality
> >>> cannot not be created from ftrace/kprobe/eBPF/whatever is reasonable.
> >>
> >> Fully agreed and this is especially true for a change this size
> >> 77 files changed, 3406 insertions(+), 703 deletions(-)
> >
> > In the case of memory allocation accounting, you flat cannot do this with ftrace
> > - you could maybe do a janky version that isn't fully accurate, much slower,
> > more complicated for the developer to understand and debug and more complicated
> > for the end user.
> >
> > But please, I invite anyone who's actually been doing this with ftrace to
> > demonstrate otherwise.
> >
> > Ftrace just isn't the right tool for the job here - we're talking about adding
> > per callsite accounting to some of the fastest fast paths in the kernel.
> >
> > And the size of the changes for memory allocation accounting are much more
> > reasonable:
> > 33 files changed, 623 insertions(+), 99 deletions(-)
> >
> > The code tagging library should exist anyways, it's been open coded half a dozen
> > times in the kernel already.
>
> Hi Kent,
>
> independent of the other discussions, if it's open coded already, does
> it make sense to factor that already-open-coded part out independently
> of the remainder of the full series here?

It's discussed in the cover letter, that is exactly how the patch series is
structured.

> [I didn't immediately spot if this series also attempts already to
> replace that open-coded part]

Uh huh.

Honestly, some days it feels like lkml is just as bad as slashdot, with people
wanting to get in their two cents without actually reading...