performance testing of UNWIND kernel option
martix.cz at gmail.com
Tue Mar 8 17:00:05 CET 2011
Ok, it is reasonable to keep CONFIG_ARM_UNWIND enabled when this
option have no practical effect on performance or latency in kernel.
So, keep it enabled. :-)
Martin 'Martix' Holec
openmoko.cz / openmobility.cz
2011/3/8 Gennady Kupava <gb at bsdmn.com>:
> 1. UNWIND do not influence performance, so enabling it should make no
> harm (according to kernel doc, i trust em 99.9%).
> 2. ability to get stack trace is widely accepted bare minimum of debug
> info, this is info is _really_ (not like other hardly usable debugging
> stuff were enabled earlier) invaluable for fixing and identifying
> problems found.
> So, no reason remove both. It is even kind of switch in kernel config
> turn on UNWIND -> FRAME_POINTER turns off. No affect on performance, add
> ability to identify problem -> must have IMO.
> В Втр, 08/03/2011 в 16:40 +0100, Martix пишет:
>> thanks for comparison.
>> I miss test with both CONFIG_ARM_UNWIND and CONFIG_FRAME_POINTER
>> disabled, theoreticaly it could be faster. Anyway, why regular user
>> (no developer, nor tester) needs to have CONFIG_ARM_UNWIND or
>> CONFIG_FRAME_POINTER enabled? I suggest to disable CONFIG_ARM_UNWIND
>> in stable kernel images. Stable I mean (in this case) kernel versions
>> which is well tested in SHR-t and stable revisions of Qt Moko.
>> Thanks Denis and Gennady.
>> Martin 'Martix' Holec
>> 2011/3/8 Gennady Kupava <gb at bsdmn.com>:
>> > Hi, list.
>> > Today I noticed the following change in SHR:
>> > http://git.openembedded.org/cgit.cgi/openembedded/commit/?id=1516588acd3c4b4dd4add71d06ab8ce0d1bafa02 (by Denis 'GNUtoo' Carikli <GNUtoo at no-log.org>) and decided to lmbench it.
>> > Here are results: http://www.bsdmn.com/lmbench/unwind_summary.txt
>> > You can see comparison of:
>> > 34def -> kernel with CONFIG_FRAME_POINTER
>> > unwind -> kernel with CONFIG_ARM_UNWIND
>> > default -> for reference, old debugging kernel
>> > The unwind option provide clear benefit of 5%-10% in almost every area.
>> > Nice spot Denis!
>> > Gennady.
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