Commit 0cf3c2fc authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Alexei Starovoitov
Browse files

samples: bpf: Add BPF support for cpumap tracepoints 



These are invoked in two places, when the XDP frame or SKB (for generic
XDP) enqueued to the ptr_ring (cpumap_enqueue) and when kthread processes
the frame after invoking the CPUMAP program for it (returning stats for
the batch).

We use cpumap_map_id to filter on the map_id as a way to avoid printing
incorrect stats for parallel sessions of xdp_redirect_cpu.

Signed-off-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210821002010.845777-9-memxor@gmail.com
parent 82c45080

samples/bpf/xdp_sample.bpf.c

+57 −1
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 


array_map rx_cnt SEC(".maps");

array_map redir_err_cnt SEC(".maps");

array_map cpumap_enqueue_cnt SEC(".maps");

array_map cpumap_kthread_cnt SEC(".maps");

array_map exception_cnt SEC(".maps");



const volatile int nr_cpus = 0;
@@ -19,6 +21,8 @@ const volatile int nr_cpus = 0; 
const volatile int from_match[32] = {};

const volatile int to_match[32] = {};



int cpumap_map_id = 0;



/* Find if b is part of set a, but if a is empty set then evaluate to true */

#define IN_SET(a, b)                                                 \

	({                                                           \
@@ -112,6 +116,59 @@ int BPF_PROG(tp_xdp_redirect_map, const struct net_device *dev, 
	return xdp_redirect_collect_stat(dev->ifindex, err);

}



SEC("tp_btf/xdp_cpumap_enqueue")

int BPF_PROG(tp_xdp_cpumap_enqueue, int map_id, unsigned int processed,

	     unsigned int drops, int to_cpu)

{

	u32 cpu = bpf_get_smp_processor_id();

	struct datarec *rec;

	u32 idx;



	if (cpumap_map_id && cpumap_map_id != map_id)

		return 0;



	idx = to_cpu * nr_cpus + cpu;

	rec = bpf_map_lookup_elem(&cpumap_enqueue_cnt, &idx);

	if (!rec)

		return 0;

	NO_TEAR_ADD(rec->processed, processed);

	NO_TEAR_ADD(rec->dropped, drops);

	/* Record bulk events, then userspace can calc average bulk size */

	if (processed > 0)

		NO_TEAR_INC(rec->issue);

	/* Inception: It's possible to detect overload situations, via

	 * this tracepoint.  This can be used for creating a feedback

	 * loop to XDP, which can take appropriate actions to mitigate

	 * this overload situation.

	 */

	return 0;

}



SEC("tp_btf/xdp_cpumap_kthread")

int BPF_PROG(tp_xdp_cpumap_kthread, int map_id, unsigned int processed,

	     unsigned int drops, int sched, struct xdp_cpumap_stats *xdp_stats)

{

	struct datarec *rec;

	u32 cpu;



	if (cpumap_map_id && cpumap_map_id != map_id)

		return 0;



	cpu = bpf_get_smp_processor_id();

	rec = bpf_map_lookup_elem(&cpumap_kthread_cnt, &cpu);

	if (!rec)

		return 0;

	NO_TEAR_ADD(rec->processed, processed);

	NO_TEAR_ADD(rec->dropped, drops);

	NO_TEAR_ADD(rec->xdp_pass, xdp_stats->pass);

	NO_TEAR_ADD(rec->xdp_drop, xdp_stats->drop);

	NO_TEAR_ADD(rec->xdp_redirect, xdp_stats->redirect);

	/* Count times kthread yielded CPU via schedule call */

	if (sched)

		NO_TEAR_INC(rec->issue);

	return 0;

}



SEC("tp_btf/xdp_exception")

int BPF_PROG(tp_xdp_exception, const struct net_device *dev,

	     const struct bpf_prog *xdp, u32 act)
@@ -136,4 +193,3 @@ int BPF_PROG(tp_xdp_exception, const struct net_device *dev, 


	return 0;

}