* dave_sperry@xxxxxxxx <dasperry@xxxxxxxxxxx> 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@xxxxxxx>
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@xxxxxxx>
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);
}
-
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