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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Mon, 5 Sep 2022 11:08:21 -0700
Message-ID: <CAJuCfpF-O6Gz2o7YqCgFHV+KEFuzC-PTUoBHj25DNRkkSmhbUg@mail.gmail.com>
Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Michal Hocko <mhocko@suse.com>,
        Kent Overstreet <kent.overstreet@linux.dev>,
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On Mon, Sep 5, 2022 at 8:06 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Sun, 4 Sep 2022 18:32:58 -0700
> Suren Baghdasaryan <surenb@google.com> wrote:
>
> > Page allocations (overheads are compared to get_free_pages() duration):
> > 6.8% Codetag counter manipulations (__lazy_percpu_counter_add + __alloc_tag_add)
> > 8.8% lookup_page_ext
> > 1237% call stack capture
> > 139% tracepoint with attached empty BPF program
>
> Have you tried tracepoint with custom callback?
>
> 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 }
> }
>
> [..]
>         register_trace_kmem_alloc(my_callback, my_data);
>
> Now the my_callback function will be called directly every time the
> kmem_alloc tracepoint is hit.
>
> This avoids that perf and BPF overhead.

Haven't tried that yet but will do. Thanks for the reference code!

>
> -- Steve