From e222833e3915daacf8e22d97290a6e901206a405 Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Wed, 23 May 2012 14:56:20 -0700 Subject: [PATCH] dpif-linux: Avoid pessimal behavior when kernel-to-user buffers overflow. When a kernel-to-user Netlink buffer overflows, the kernel reports ENOBUFS without passing along an actual message. When it does this, we should immediately try again, because we know that there is a message waiting, instead of reporting the error to the caller. This improves the OVS response rate to "hping3 --flood" traffic by a few percentage points in my testing. Signed-off-by: Ben Pfaff --- lib/dpif-linux.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/lib/dpif-linux.c b/lib/dpif-linux.c index 256c9d6c..9d84edd0 100644 --- a/lib/dpif-linux.c +++ b/lib/dpif-linux.c @@ -150,6 +150,7 @@ struct dpif_linux { }; static struct vlog_rate_limit error_rl = VLOG_RATE_LIMIT_INIT(9999, 5); +static struct vlog_rate_limit enobufs_rl = VLOG_RATE_LIMIT_INIT(60, 5); /* Generic Netlink family numbers for OVS. */ static int ovs_datapath_family; @@ -1138,6 +1139,15 @@ dpif_linux_recv(struct dpif *dpif_, struct dpif_upcall *upcall, error = nl_sock_recv(upcall_sock, buf, false); if (error) { + if (error == ENOBUFS) { + /* ENOBUFS typically means that we've received so many + * packets that the buffer overflowed. Try again + * immediately because there's almost certainly a packet + * waiting for us. */ + VLOG_ERR_RL(&enobufs_rl, "%s: lost packet with hash %d", + dpif_name(dpif_), dpif->ready_mask); + continue; + } if (error == EAGAIN) { break; } -- 2.30.2