Commit bb024780 authored by Lorenzo Bianconi's avatar Lorenzo Bianconi Committed by Daniel Borkmann
Browse files

bpf, cpumap: Bulk skb using netif_receive_skb_list 



Rely on netif_receive_skb_list routine to send skbs converted from
xdp_frames in cpu_map_kthread_run in order to improve i-cache usage.
The proposed patch has been tested running xdp_redirect_cpu bpf sample
available in the kernel tree that is used to redirect UDP frames from
ixgbe driver to a cpumap entry and then to the networking stack. UDP
frames are generated using pktgen. Packets are discarded by the UDP
layer.

$ xdp_redirect_cpu  --cpu <cpu> --progname xdp_cpu_map0 --dev <eth>

bpf-next: ~2.35Mpps
bpf-next + cpumap skb-list: ~2.72Mpps

Rename drops counter in kmem_alloc_drops since now it reports just
kmem_cache_alloc_bulk failures

Signed-off-by: default avatarLorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/bpf/c729f83e5d7482d9329e0f165bdbe5adcefd1510.1619169700.git.lorenzo@kernel.org
parent 10bf4e83

kernel/bpf/cpumap.c

+9 −9
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ 
#include <linux/capability.h>

#include <trace/events/xdp.h>



#include <linux/netdevice.h>   /* netif_receive_skb_core */

#include <linux/netdevice.h>   /* netif_receive_skb_list */

#include <linux/etherdevice.h> /* eth_type_trans */



/* General idea: XDP packets getting XDP redirected to another CPU,
@@ -252,11 +252,12 @@ static int cpu_map_kthread_run(void *data) 
	 */

	while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {

		struct xdp_cpumap_stats stats = {}; /* zero stats */

		unsigned int kmem_alloc_drops = 0, sched = 0;

		gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;

		unsigned int drops = 0, sched = 0;

		void *frames[CPUMAP_BATCH];

		void *skbs[CPUMAP_BATCH];

		int i, n, m, nframes;

		LIST_HEAD(list);



		/* Release CPU reschedule checks */

		if (__ptr_ring_empty(rcpu->queue)) {
@@ -297,7 +298,7 @@ static int cpu_map_kthread_run(void *data) 
			if (unlikely(m == 0)) {

				for (i = 0; i < nframes; i++)

					skbs[i] = NULL; /* effect: xdp_return_frame */

				drops += nframes;

				kmem_alloc_drops += nframes;

			}

		}
@@ -305,7 +306,6 @@ static int cpu_map_kthread_run(void *data) 
		for (i = 0; i < nframes; i++) {

			struct xdp_frame *xdpf = frames[i];

			struct sk_buff *skb = skbs[i];

			int ret;



			skb = __xdp_build_skb_from_frame(xdpf, skb,

							 xdpf->dev_rx);
@@ -314,13 +314,13 @@ static int cpu_map_kthread_run(void *data) 
				continue;

			}



			/* Inject into network stack */

			ret = netif_receive_skb_core(skb);

			if (ret == NET_RX_DROP)

				drops++;

			list_add_tail(&skb->list, &list);

		}

		netif_receive_skb_list(&list);



		/* Feedback loop via tracepoint */

		trace_xdp_cpumap_kthread(rcpu->map_id, n, drops, sched, &stats);

		trace_xdp_cpumap_kthread(rcpu->map_id, n, kmem_alloc_drops,

					 sched, &stats);



		local_bh_enable(); /* resched point, may call do_softirq() */

	}