Venki
acpi_cpufreq_target uses 3144 of stack on a big NR_CPUS box below
cpu_idle_wait uses 2568
looks like cpumask_t on the stack may not be a great idea...
-Len
---------- Forwarded Message ----------
Subject: Re: [PATCH 4/5] x86: Add config variables for SMP_MAX
Date: Friday 18 January 2008 15:14
From: Mike Travis <travis@xxxxxxx>
To: Ingo Oeser <ioe-lkml@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxxx>, mingo@xxxxxxx, Christoph Lameter <clameter@xxxxxxx>, linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Ingo Oeser wrote:
> Hi Mike,
>
> On Friday 18 January 2008, travis@xxxxxxx wrote:
>> +config THREAD_ORDER
>> + int "Kernel stack size (in page order)"
>> + range 1 3
>> + depends on X86_64_SMP
>> + default "3" if X86_SMP_MAX
>> + default "1"
>> + help
>> + Increases kernel stack size.
>> +
>
> Could you please elaborate, why this is needed and put more info about
> this requirement into this patch description?
>
> People worked hard to push data allocation from stack to heap to make
> THREAD_ORDER of 0 and 1 possible. So why increase it again and why does this
> help scalability?
>
> Many thanks and Best Regards
>
> Ingo Oeser, puzzled a bit :-)
The primary problem arises because of cpumask_t local variables. Until I
can deal with these, increasing NR_CPUS to a really large value increases
stack size dramatically.
Here are the top stack consumers with NR_CPUS = 4k.
16392 isolated_cpu_setup
10328 build_sched_domains
8248 numa_initmem_init
4664 cpu_attach_domain
4104 show_shared_cpu_map
3656 centrino_target
3608 powernowk8_cpu_init
3192 sched_domain_node_span
3144 acpi_cpufreq_target
2584 __svc_create_thread
2568 cpu_idle_wait
2136 netxen_nic_flash_print
2104 powernowk8_target
2088 _cpu_down
2072 cache_add_dev
2056 get_cur_freq
0 acpi_processor_ffh_cstate_probe
2056 microcode_write
0 acpi_processor_get_throttling
2048 check_supported_cpu
And I've yet to figure out how to accumulate stack sizes using
call threads.
Thanks,
Mike
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