On Thursday 2011-02-03 22:10, David Miller wrote:
>>I remember there being a kernel config option
>>(CONFIG_DEBUG_STACKOVERFLOW) that would emit messages similar to
>>"process foobar (12345) used greatest stack depth: 2042" -- would
>>that also work for softirqs?
>
>The kernel stack tracer is your best bet right now, it's easy to
>enable, it's something like just writing "1" to the /sys filesystem
>file that controls it.
>
>config STACK_TRACER
> This special tracer records the maximum stack footprint of the
> kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
>
> This tracer works by hooking into every function call that the
> kernel executes, and keeping a maximum stack depth value and
> stack-trace saved. If this is configured with DYNAMIC_FTRACE
> then it will not have any overhead while the stack tracer
> is disabled.
Compiled with DYNAMIC_FTRACE=y, and enabled (writing 1
to /sys/kernel/debug/tracing/tracing_enabled). In the stack_trace
file I can find some lines..
Depth Size Location (56 entries)
----- ---- --------
0) 5496 48 stack_trace_call+0xfa/0x1aa
1) 5448 112 ftrace_call+0x5/0x2b
2) 5336 64 zone_watermark_ok+0x29/0xbf
3) 5272 288 get_page_from_freelist+0x1b7/0x6ab
4) 4984 240 __alloc_pages_nodemask+0x11b/0x70e
5) 4744 48 kmem_getpages+0x65/0x10e
6) 4696 128 cache_grow+0xc4/0x285
7) 4568 96 ____cache_alloc+0x21e/0x26d
8) 4472 64 kmem_cache_alloc+0x5e/0xfb
9) 4408 16 mempool_alloc_slab+0x15/0x17
10) 4392 144 mempool_alloc+0x52/0x104
11) 4248 32 scsi_sg_alloc+0x2d/0x2f
etc.
Does the file cover all CPUs and past function executions, is there a
timeout on these entries? At other times, running cat on that file
merely yields 2 entries, being the stack tracing itself.
Will this list dumped to the console in case of a
bug/oops/Illegal_IP?
thanks,
Jan
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