Re: [PATCH 1/1] Implement shared page tables

[Martin J. Bligh]

>> They're incompatible, but you could be left to choose one or the other
>> via config option.
> 
> Wouldn't need config option: there's /proc/sys/kernel/randomize_va_space
> for the whole running system, compatibility check on the ELFs run, and
> the infinite stack rlimit: enough ways to suppress randomization if it
> doesn't suit you.

Even better - much easier to deal with distro stuff if we can do it at
runtime.
 
>> 3% on "a certain industry-standard database benchmark" (cough) is huge,
>> and we expect the benefit for PPC64 will be larger as we can share the
>> underlying hardware PTEs without TLB flushing as well.
> 
> Okay - and you're implying that 3% comes from _using_ the shared page
> tables, rather than from avoiding the fork/exit overhead of setting
> them up and tearing them down.  And it can't use huge TLB pages
> because...  fragmentation?

Yes - as I understand it, that was a straight measurement with/without the
patch, and the shmem segment was already using hugetlb (in both cases). 
Yes, I find that a bit odd as to why as well - they are still trying 
to get some detailed profiling to explain. 

M.

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