From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Frank Blaschka reported :
<quote>
During heavy network load we turn off/on cpus.
Sometimes this causes a stall on the network device.
Digging into the dump I found out following:
napi is scheduled but does not run. From the I/O buffers
and the napi state I see napi/rx_softirq processing has stopped
because the budget was reached. napi stays in the
softnet_data poll_list and the rx_softirq was raised again.
I assume at this time the cpu offline comes in,
the rx softirq is raised/moved to another cpu but napi stays in the
poll_list of the softnet_data of the now offline cpu.
Reviewing dev_cpu_callback (net/core/dev.c) I did not find the
poll_list is transfered to the new cpu.
</quote>
This patch is a straightforward implementation of Frank suggestion :
Transfert poll_list and trigger NET_RX_SOFTIRQ on new cpu.
Reported-by: Frank Blaschka <blaschka@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Tested-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
---
While doing my tests on bnx2x adapter, I found patch was working ok,
but /proc/interrupts still increment interrupt count on my offlined
cpu... go figure...
net/core/dev.c | 5 +++++
1 files changed, 5 insertions(+)
diff --git a/net/core/dev.c b/net/core/dev.c
index 9393078..095909c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6178,6 +6178,11 @@ static int dev_cpu_callback(struct notifier_block *nfb,
oldsd->output_queue = NULL;
oldsd->output_queue_tailp = &oldsd->output_queue;
}
+ /* Append NAPI poll list from offline CPU. */
+ if (!list_empty(&oldsd->poll_list)) {
+ list_splice_init(&oldsd->poll_list, &sd->poll_list);
+ raise_softirq_irqoff(NET_RX_SOFTIRQ);
+ }
raise_softirq_irqoff(NET_TX_SOFTIRQ);
local_irq_enable();
--
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