On Mon, Sep 5, 2022 at 8:06 AM Steven Rostedt [off-list ref] wrote:

On Sun, 4 Sep 2022 18:32:58 -0700
Suren Baghdasaryan [off-list ref] wrote:

quoted

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