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

Kent Overstreet
2022-09-05T23:51:29Z

On Mon, Sep 05, 2022 at 06:16:50PM -0400, Steven Rostedt wrote:
> On Mon, 5 Sep 2022 16:42:29 -0400
> Kent Overstreet <kent.overstreet@linux.dev> wrote:
>
> > > Haven't tried that yet but will do. Thanks for the reference code!
> >
> > Is it really worth the effort of benchmarking tracing API overhead here?
> >
> > The main cost of a tracing based approach is going to to be the data structure
> > for remembering outstanding allocations so that free events can be matched to
> > the appropriate callsite. Regardless of whether it's done with BFP or by
> > attaching to the tracepoints directly, that's going to be the main overhead.
>
> The point I was making here is that you do not need your own hooking
> mechanism. You can get the information directly by attaching to the
> tracepoint.
>
> > > static void my_callback(void *data, unsigned long call_site,
> > > const void *ptr, struct kmem_cache *s,
> > > size_t bytes_req, size_t bytes_alloc,
> > > gfp_t gfp_flags)
> > > {
> > > struct my_data_struct *my_data = data;
> > >
> > > { do whatever }
> > > }
>
> The "do whatever" is anything you want to do.
>
> Or is the data structure you create with this approach going to be too much
> overhead? How hard is it for a hash or binary search lookup?

If you don't think it's hard, go ahead and show us.