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Performance bug while ordering .text sections by default in gold.

Xinliang David Li davidxl@google.com
Tue Jan 22 19:49:00 GMT 2013 
Sri, I have not looked at the details of the patch, but does it
recover the behavior before the 2012-12 patch mentioned? If not, it
then introduces another variance that may impact performance. For the
time being, I think it is better to restore the old layout to recover
the performance regressions. A complete fix may require more time to
do performance tuning and can be done as a followup.

thanks,

David

On Tue, Jan 22, 2013 at 11:35 AM, Sriraman Tallam <tmsriram@google.com> wrote:
> Hi,
>
>    This patch to gold :
> http://sourceware.org/ml/binutils/2012-12/msg00227.html introduces
> unnecessary behaviour while ordering text sections and this is causing
> performance regressions in some benchmarks.  The intent of this patch
> was to group .text sections with special prefixes like ".text.hot",
> ".text.unlikely" , ".text.startup" together, which it achieves.
> However, it does other undesired things too like sorting section names
> of those sections without these special prefixes.  This is because it
> uses the compare function "Input_section_sort_compare" which was used
> to sort ".ctors" and ".dtors". Sorting by section names can cause
> undesired ordering like splitting functions in the same module.
>
>    I am fixing this by making ".text" default sorting use the sort
> function Input_section_sort_section_order_index_compare.  I think this
> is better as the different comparison criteria are much less and is
> all applicable to ".text" under different contexts.
>
>   Patch attached.
>
> Thanks
> Sri
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