On 01/08/2011 04:20 PM, Felix Fietkau wrote:
On 2011-01-08 8:33 AM, greearb@xxxxxxxxxxxxxxx wrote:From: Ben Greear<greearb@xxxxxxxxxxxxxxx> This saves us constantly allocating large, multi-page skbs. It should fix the order-1 allocation errors reported, and in a 60-vif scenario, this significantly decreases CPU utilization, and latency, and increases bandwidth. Signed-off-by: Ben Greear<greearb@xxxxxxxxxxxxxxx> --- :100644 100644 b2497b8... ea2f67c... M drivers/net/wireless/ath/ath9k/recv.c drivers/net/wireless/ath/ath9k/recv.c | 92 ++++++++++++++++++++++----------- 1 files changed, 61 insertions(+), 31 deletions(-) diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c index b2497b8..ea2f67c 100644 --- a/drivers/net/wireless/ath/ath9k/recv.c +++ b/drivers/net/wireless/ath/ath9k/recv.c @@ -1702,42 +1704,70 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp) unlikely(tsf_lower - rs.rs_tstamp> 0x10000000)) rxs->mactime += 0x100000000ULL; - /* Ensure we always have an skb to requeue once we are done - * processing the current buffer's skb */ - requeue_skb = ath_rxbuf_alloc(common, common->rx_bufsize, GFP_ATOMIC); - - /* If there is no memory we ignore the current RX'd frame, - * tell hardware it can give us a new frame using the old - * skb and put it at the tail of the sc->rx.rxbuf list for - * processing. */ - if (!requeue_skb) - goto requeue; - - /* Unmap the frame */ - dma_unmap_single(sc->dev, bf->bf_buf_addr, - common->rx_bufsize, - dma_type); + len = rs.rs_datalen + ah->caps.rx_status_len; + if (use_copybreak) { + skb = netdev_alloc_skb(NULL, len); + if (!skb) { + skb = bf->bf_mpdu; + use_copybreak = false; + goto non_copybreak; + } + } else {I think this should be dependent on packet size, maybe even based on the architecture. Especially on embedded hardware, copying large frames is probably quite a bit more expensive than allocating large buffers. Cache sizes are small, memory access takes several cycles, especially during concurrent DMA. Once I'm back home, I could try a few packet size threshold to find a sweet spot for the typical MIPS hardware that I'm playing with. I expect a visible performance regression from this patch when applied as-is.
I see a serious performance improvement with this patch. My current test is sending 1024 byte UDP payloads to/from each of 60 stations at 128kbps. Please do try it out on your system and see how it performs there. I'm guessing that any time you have more than 1 VIF this will be a good improvement since mac80211 does skb_copy (and you would typically be copying a much smaller packet with this patch). If we do see performance differences on different platforms, this could perhaps be something we could tune at run-time. Thanks, Ben
- Felix
-- Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc http://www.candelatech.com -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
