From 6dba29a285d0527ec1cd408cbba3496f91b68113 Mon Sep 17 00:00:00 2001 From: Luigi Rizzo Date: Fri, 13 Jan 2012 10:21:15 +0000 Subject: Two performance-related fixes: 1. as reported by Alexander Fiveg, the allocator was reporting half of the allocated memory. Fix this by exiting from the loop earlier (not too critical because this code is going away soon). 2. following a discussion on freebsd-current http://lists.freebsd.org/pipermail/freebsd-current/2012-January/031144.html turns out that (re)loading the dmamap was expensive and not optimized. This operation is in the critical path when doing zero-copy forwarding between interfaces. At least on netmap and i386/amd64, the bus_dmamap_load can be completely bypassed if the map is NULL, so we do it. The latter change gives an almost 3x improvement in forwarding performance, from the previous 9.5Mpps at 2.9GHz to the current line rate (14.2Mpps) at 1.733GHz. (this is for 64+4 byte packets, in other configurations the PCIe bus is a bottleneck). --- sys/dev/netmap/netmap_kern.h | 37 +++++++++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 8 deletions(-) (limited to 'sys/dev/netmap/netmap_kern.h') diff --git a/sys/dev/netmap/netmap_kern.h b/sys/dev/netmap/netmap_kern.h index d35e5039f989e..4d91ec1606af4 100644 --- a/sys/dev/netmap/netmap_kern.h +++ b/sys/dev/netmap/netmap_kern.h @@ -169,16 +169,8 @@ int netmap_start(struct ifnet *, struct mbuf *); enum txrx { NR_RX = 0, NR_TX = 1 }; struct netmap_slot *netmap_reset(struct netmap_adapter *na, enum txrx tx, int n, u_int new_cur); -void netmap_load_map(bus_dma_tag_t tag, bus_dmamap_t map, void *buf); -void netmap_reload_map(bus_dma_tag_t tag, bus_dmamap_t map, void *buf); int netmap_ring_reinit(struct netmap_kring *); -/* - * XXX eventually, get rid of netmap_total_buffers and netmap_buffer_base - * in favour of the structure - */ -// struct netmap_buf_pool; -// extern struct netmap_buf_pool nm_buf_pool; extern u_int netmap_total_buffers; extern char *netmap_buffer_base; extern int netmap_verbose; // XXX debugging @@ -203,6 +195,35 @@ enum { /* verbose flags */ #define NA(_ifp) ((struct netmap_adapter *)WNA(_ifp)) +/* Callback invoked by the dma machinery after a successfull dmamap_load */ +static void netmap_dmamap_cb(__unused void *arg, + __unused bus_dma_segment_t * segs, __unused int nseg, __unused int error) +{ +} + +/* bus_dmamap_load wrapper: call aforementioned function if map != NULL. + * XXX can we do it without a callback ? + */ +static inline void +netmap_load_map(bus_dma_tag_t tag, bus_dmamap_t map, void *buf) +{ + if (map) + bus_dmamap_load(tag, map, buf, NETMAP_BUF_SIZE, + netmap_dmamap_cb, NULL, BUS_DMA_NOWAIT); +} + +/* update the map when a buffer changes. */ +static inline void +netmap_reload_map(bus_dma_tag_t tag, bus_dmamap_t map, void *buf) +{ + if (map) { + bus_dmamap_unload(tag, map); + bus_dmamap_load(tag, map, buf, NETMAP_BUF_SIZE, + netmap_dmamap_cb, NULL, BUS_DMA_NOWAIT); + } +} + + /* * NMB return the virtual address of a buffer (buffer 0 on bad index) * PNMB also fills the physical address -- cgit v1.3