Messages in this thread Patch in this message |  | | | Date | Mon, 2 Apr 2007 21:04:45 +0200 | | From | Ingo Molnar <> | | Subject | Re: Poor UDP performance using 2.6.21-rc5-rt5 |
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* dave_sperry@ieee.org <dasperry@comcast.net> wrote:
> The Intel NIC seems to behave better under RT
yeah.
> I think there is some kind of bad behavior happening in the Nvidia > driver with respect to softirq-net-tx and IRQ-8406.
yes. Part of the problem is that the forcedeth.c driver does not fully support NAPI - today i've implemented those bits (see them below), based on your testcase. The other part is that the Intel NIC uses MSI, while foredeth uses fasteoi, correct? [you can see this in /proc/interrupts]
there are a few other things i'm working on to improve this. I've uploaded -rt9 which is the current state of affairs. Note that using -rt9 you'll likely only see IRQ-8406 overhead in the system, because i've added an optimization to do process the softirq-net-tx workload in the hardirq thread if the priority of the two is the same (which is the default behavior). But -rt9 is still work in progress that is not fully finished yet: in some cases i'm seeing 'fluctuating performance' problems on forcedeth that werent there before.
Ingo
---------------------> From: Ingo Molnar <mingo@elte.hu> Subject: [patch] forcedeth.c: improve NAPI handler another forcedeth.c thing: i noticed that its NAPI handler does not do tx-ring processing. The patch below implements this - tested on DESC_VER_2 hardware, with CONFIG_FORCEDETH_NAPI=y.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Index: linux/drivers/net/forcedeth.c =================================================================== --- linux.orig/drivers/net/forcedeth.c +++ linux/drivers/net/forcedeth.c @@ -3118,9 +3118,17 @@ static int nv_napi_poll(struct net_devic int retcode; if (np->desc_ver == DESC_VER_1 || np->desc_ver == DESC_VER_2) { + spin_lock_irqsave(&np->lock, flags); + nv_tx_done(dev); + spin_unlock_irqrestore(&np->lock, flags); + pkts = nv_rx_process(dev, limit); retcode = nv_alloc_rx(dev); } else { + spin_lock_irqsave(&np->lock, flags); + nv_tx_done_optimized(dev, np->tx_ring_size); + spin_unlock_irqrestore(&np->lock, flags); + pkts = nv_rx_process_optimized(dev, limit); retcode = nv_alloc_rx_optimized(dev); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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