[cgl_discussion] Re: [PATCH i386] Live Patching Function on 2.6.11.7

Andrew Morton akpm at osdl.org
Fri Apr 29 02:47:25 PDT 2005


Takashi Ikebe <ikebe.takashi at lab.ntt.co.jp> wrote:
>
> This patch add function called "Live patching" which is defined on
>  OSDL's carrier grade linux requiremnt definition to linux 2.6.11.7 kernel.

I must say that I'd agree with the hostile reception which this work
received on the linux-kernel list.

It needs to be exhaustively demonstrated that this functionality cannot be
provided in userspace.  If it can be implemented in userspace then it would
be via a library and would require basically zero modifications to legacy
applications.

If PTRACE_PEEKTEXT/POKETEXT ends up being a limiting factor then we would
certainly support extensions to the ptrace function which enable higher
throughput - presumably with scatter/gather lists.

To repeat: I think it _can_ be done in userspace - if the implementation is
sufficiently good then the limiting factor would be memory bandwidth.

We've seen assertions that a userspace approach would be too slow, but to
get support for a patch like this, quite frankly, we'd need to see the
too-slow userspace implementation before we'd agree that kernel help is
needed.




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