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SubjectRe: irq-disabled vs vmap vs text_poke

On Tue, 17 Feb 2009, Masami Hiramatsu wrote:
>
> Thanks, I think text_poke() doesn't need high performance currently,
> because it's not called so frequently, nor from the normal operation.
>
> However, Would dynamic ftrace need performance?

Are you talking about replacing what dynamic ftrace does now with
text_poke? Well, It takes just under a second right now to do all the
conversions. Looking at the list on my booted box, it converts 19805
locations. It takes care to run stop machine, and it also has code to
handle NMIs on the other CPUS while it runs.

Changing text must be done extremely carefully on a running box. If the
code being changed is also executed on another CPU then you will most
likely take a GPF on that CPU.

Also, every arch must do things a bit different, due to the way modules
are handled.

-- Steve



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