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dpif-linux: Avoid pessimal behavior when kernel-to-user buffers overflow.

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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 <blp@nicira.com>
This commit is contained in:
Ben Pfaff
2012-05-23 14:56:20 -07:00
parent cf1b8a921b
commit e222833e39
1 changed files with 10 additions and 0 deletions
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10
lib/dpif-linux.c
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@@ -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;
}