Messages in this thread Patch in this message |  | | | Date | Mon, 30 Aug 2004 21:21:31 +0200 | | From | Ingo Molnar <> | | Subject | Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q5 |
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* Mark_H_Johnson@raytheon.com <Mark_H_Johnson@raytheon.com> wrote:
> LONG NETWORK LATENCIES > ====================== > > In about 25 minutes of heavy testing, I had two latency traces with > /proc/sys/kernel/preempt_max_latency set to 700. They had the same start / > end location with the long delay as follows: > 730 us, entries: 361 > ... > started at rtl8139_poll+0x3c/0x160 > ended at rtl8139_poll+0x100/0x160
regarding this particular latency, could you try the attached patch ontop of -Q5? It turns the ->poll() loop into separate, individually preemptable iterations instead of one batch of processing. In theory this should result in latency being lower regardless of the netdev_max_backlog value.
Ingo --- linux/net/core/dev.c.orig2 +++ linux/net/core/dev.c @@ -1903,7 +1903,7 @@ static void net_rx_action(struct softirq { struct softnet_data *queue = &__get_cpu_var(softnet_data); unsigned long start_time = jiffies; - int budget = netdev_max_backlog; + int budget = netdev_max_backlog, loops; local_irq_disable(); @@ -1926,7 +1926,10 @@ static void net_rx_action(struct softirq dev = list_entry(queue->poll_list.next, struct net_device, poll_list); - if (dev->quota <= 0 || dev->poll(dev, &budget)) { + loops = 1; + if (dev->quota <= 0 || dev->poll(dev, &loops)) { + if (loops < 1) + budget--; local_irq_disable(); list_del(&dev->poll_list); list_add_tail(&dev->poll_list, &queue->poll_list);
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