Re: FOR REVIEW: New x86-64 vsyscall vgetcpu()
From: Zoltan Menyhart
Date: Fri Jun 16 2006 - 11:30:06 EST
Andi Kleen wrote:
That is not how user space TLS works. It usually has a base a register.
Can you please give me a real life (simplified) example?
This means it cannot be cache colored (because you would need a static
offset) and you couldn't share task_structs on a page.
I do not see the problem. Can you explain please?
E.g. the scheduler pulls a task instead of the current one. The CPU
will see "current->thread_info.cpu"-s of all the tasks at the same
offset anyway.
Also you would make task_struct part of the userland ABI which
seems like a very very bad idea to me. It means we couldn't change
it anymore.
We can make some wrapper, e.g.:
user_per_cpu_var(name, offset)
"vgetcpu()" would also be added to the ABI which we couldn't change
easily either.
Thanks,
Zoltan
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