nfp: bpf: add short busy wait for FW replies

Scheduling out and in for every FW message can slow us down
unnecessarily.  Our experiments show that even under heavy load
the FW responds to 99.9% messages within 200 us.  Add a short
busy wait before entering the wait queue.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c b/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
index 71e6586acc367518934be289268ec5ce08f4fd1c..80d3aa0fc9d3ed817b10a0cdba97d95d48d5a326 100644 (file)
--- a/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/cmsg.c
@@ -157,7 +157,14 @@ nfp_bpf_cmsg_wait_reply(struct nfp_app_bpf *bpf, enum nfp_bpf_cmsg_type type,
                        int tag)
 {
        struct sk_buff *skb;
-       int err;
+       int i, err;
+
+       for (i = 0; i < 50; i++) {
+               udelay(4);
+               skb = nfp_bpf_reply(bpf, tag);
+               if (skb)
+                       return skb;
+       }
 
        err = wait_event_interruptible_timeout(bpf->cmsg_wq,
                                               skb = nfp_bpf_reply(bpf, tag),