Re: 46% performance drop with change in glibc

[Andrew Theurer <habanero@us.ibm.com>]

Ian Pratt wrote:

>>>>The crippled ABI is supported by the code in /lib/i686/nosegneg.  
>>>>This code is *automatically* used if the kernel is 
>>>>
>>compiled to match 
>>
>>>>the glibc version.  This happens using the
>>>>
>>>>linux-2.6-xen-vdso-note.patch
>>>>
>>>I believe we have this patch in the xen repo, but I haven't ever 
>>>verified whether the right thing happens under FC4.
>>>
>>I am not seeing this patch in ./patches/linux-2.6.12 
>>directory.  Is it somewhere else?
>>
>
>It should be in the main tree. The appended patch was included some time
>ago, but I've never tested it to see whether it works since I don't
>generally run bleeding edge Fedora.
>
>Is there some piece of the patch missing?
>
No, it's all there.  Only part I needed was the change to ld.so.conf.  
So, anyone with FC4, you might want to make sure you have the entry 
"hwcap 0 nosegneg".  It looks like the performance regression has 
disappeared now.  Thanks all for you help.

-Andrew