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Date:   Mon, 5 Sep 2022 19:50:07 -0400
From:   Kent Overstreet <kent.overstreet@linux.dev>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Suren Baghdasaryan <surenb@google.com>,
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Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications
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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.