Re: [PATCH 3/3] x86, vdso32: handle 32 bit vDSO larger one page

[H. Peter Anvin]

On 03/13/2014 11:08 AM, H. Peter Anvin wrote:
> On 03/13/2014 10:28 AM, Andy Lutomirski wrote:
>>
>> Does this mean you prefer the relocation approach to the compat vdso
>> removal approach?  It seems like Linus is okay with either one.
>>
> 
> Actually, thinking about it, removing it is probably better:
> 
> a) gets rid of legacy code, making room for unification;
> b) either way enabling compat support (either relocation or disabling
>    the vdso) has a performance penalty for *all* processes.
> 
> The only way to avoid that is to have a vdso at a fixed addresses across
> all processes, either in the fixmap or in the user area (presumably at
> the very top.)
> 

So going back and re-reading all the threads, the consensus was to
remove the compat vdso, but recycling the CONFIG_COMPAT_VDSO
configuration option name for the default-disable option.

It is important that anyone who actually cares about performance unsets
the option.

	-hpa


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