[LinuxBIOS] Long delay between messages.
yasteve at gmail.com
Fri Dec 21 22:45:06 CET 2007
On Fri, 2007-12-21 at 14:15 -0700, Marc Jones wrote:
> Try setting CONFIG_LOGICAL_CPUS 0 and see if that makes the delay go
> away. I am going to assume that is where the problem is based on the
> *01*00000001 message is probably coming from wait_ap_started().
I'll give it a try. This definitely had an effect. I'm seeing these with
only one delay now.
02 nodes initialized.
> I will attempt to give you an overview of how I think this works. First
> thing is that each APs APIC is used to hold flags about the AP(core)
> state. This is the only good way to communicate between cores (sharing
> memory can get very messy with CAR). The other flag is the
> BIOS/INIT/COLD Reset flags that set when each nodes core0 executes the
> ROM, distinguish_cpu_resets(). The core0 execution is done near the end
> of setup_coherent_ht_domain(). Then the bsp, node0core0, waits,
> wait_all_core0_started(), for node1core0 to execute and loop in
> init_cpus(). This seems to be working based on the message core0
> started: 01.
> Next is start_other_cores() and
> wait_all_other_cores_started(bsp_apicid). This is where the long delay
> is probably happening as cores are off running and the BSP is waiting. I
> don't have any idea why it is stuck waiting but you should get some
> insight by instrumenting init_cpus(), wait_cpu_state() and
Thanks for this insight. I didn't realize the importance of the APIC.
I'll follow this logic through and see what I can learn.
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