Re: [PATCH] .text page fault SMP scalability optimization

[Andrew Morton]

Andrea Arcangeli <andrea@xxxxxxx> wrote:
>
> We had a problem on ppc64 where with more than 4 threads a large system
> wouldn't scale well while faulting in the .text (most of the time was
> spent in the kernel despite it was an userland compute intensive app).
> The reason is the useless overwrite of the same pte from all cpu.
> 
> I fixed it this way (verified on an older kernel but the forward port is
> almost identical). This will benefit all archs not just ppc64.

How strange.  Do you mena that all CPUs were entering the pagefault handler
on behalf of the same pte all the time?  That they're staying in lockstep?

If so, there must be a bunch of page_table_lock contention too?
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