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authorDavid Gibson <david@gibson.dropbear.id.au>2023-01-05 15:26:21 +1100
committerStefano Brivio <sbrivio@redhat.com>2023-01-13 01:07:01 +0100
commitc9e193b5ae0d785f9d77adf2ce196393a1ab205c (patch)
tree4e9cd01a3c8c388d5ef9be874fa308d52d836ed6
parent4eb54fd2e792e2c168588c2789e8d5d5977db75d (diff)
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udp: Don't handle tap receive batch size calculation within a #define
UDP_MAX_FRAMES gives the maximum number of datagrams we'll ever handle as a batch for sizing our buffers and control structures. The subtly different UDP_TAP_FRAMES gives the maximum number of datagrams we'll actually try to receive at once for tap packets in the current configuration. This depends on the mode, meaning that the macro has a non-obvious dependency on the usual 'c' context variable being available. We only use it in one place, so it makes more sense to open code this. Add an explanatory comment while we're there. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
-rw-r--r--udp.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/udp.c b/udp.c
index 64c9219..6951c4c 100644
--- a/udp.c
+++ b/udp.c
@@ -119,7 +119,6 @@
#define UDP_CONN_TIMEOUT 180 /* s, timeout for ephemeral or local bind */
#define UDP_MAX_FRAMES 32 /* max # of frames to receive at once */
-#define UDP_TAP_FRAMES (c->mode == MODE_PASST ? UDP_MAX_FRAMES : 1)
/**
* struct udp_tap_port - Port tracking based on tap-facing source port
@@ -950,10 +949,14 @@ static void udp_tap_send(const struct ctx *c,
void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
const struct timespec *now)
{
+ /* For not entirely clear reasons (data locality?) pasta gets
+ * better throughput if we receive the datagrams one at a
+ * time.
+ */
+ ssize_t n = (c->mode == MODE_PASST ? UDP_MAX_FRAMES : 1);
in_port_t dstport = ref.r.p.udp.udp.port;
bool v6 = ref.r.p.udp.udp.v6;
struct mmsghdr *sock_mmh;
- ssize_t n;
if (events == EPOLLERR)
return;
@@ -968,7 +971,7 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
else
sock_mmh = udp4_l2_mh_sock;
- n = recvmmsg(ref.r.s, sock_mmh, UDP_TAP_FRAMES, 0, NULL);
+ n = recvmmsg(ref.r.s, sock_mmh, n, 0, NULL);
if (n <= 0)
return;