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kernel config - debug considerations

Posted on 2002-05-28
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Last Modified: 2013-12-16
I am customizing a kernel starting with a RedHat premade config file. I noticed kernel debug is selected as the default; however, I will be intending to use this kernel for "production" servers. What are the caveats/considerations, etc regarding this option. On one hand I want good info in the event of a problem, but not at te expense of a considerable (say 10-15%) speed hit.
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Question by:medent
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by:ahoffmann
ID: 7040030
which one do you mean?
  CONFIG_DEBUG_ERRORS
 
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by:medent
ID: 7040051
Here is the kernel section (default redhat config)...

CONFIG_DEBUG_KERNEL=y
# CONFIG_DEBUG_HIGHMEM is not set
# CONFIG_DEBUG_SLAB is not set
# CONFIG_DEBUG_IOVIRT is not set
CONFIG_MAGIC_SYSRQ=y
# CONFIG_DEBUG_SPINLOCK is not set
CONFIG_DEBUG_BUGVERBOSE=y
# CONFIG_HIGHMEM_EMULATION is not set
CONFIG_KALLSYMS=y

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by:ahoffmann
ID: 7040104
AFAIK you may savely unset CONFIG_DEBUG_KERNEL and also CONFIG_MAGIC_SYSRQ.
Don't know about CONFIG_DEBUG_BUGVERBOSE, probaly RH special. Probably it's useless anyway if the other 2 are unset.
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by:medent
ID: 7041425
I realize these are optional and I can safely unset them, I am looking for details to support having this on or off, what is the performance hit with debugging on, or what happens if you have a (driver,etc) problem w/o debugging on..?
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pheur earned 200 total points
ID: 7045297
CONFIG_DEBUG_BUGVERBOSE doesn't affect performance. Just takes about 100K of memory, an affordable thing these days. It sends via printk information that aids identifying a bug, after the boggy condition occurred.
CONFIG_MAGIC_SYSRQ is even recommended in production.
About support, I can't tell you anything, it's you the one that has to look in the support contract if you have something like that. Most Linux people live very happy without OS support contracts because it's either not necessary, or the skills needed to solve various problems are available in-house. I've seen LARGE companies that use Linux and only buy support for hardware.

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Radu-Adrian Feurdean
Brainbench Linux MVP
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