Re: mprotect() api overhead.

Benjamin LaHaise (
Sun, 24 Mar 2002 23:19:29 -0500

On Sat, Mar 23, 2002 at 02:20:37AM +0000, Alan Cox wrote:
> > As for SMP case, for my application, it is less an issue, since
> > when user call my API in the .so, the mprotect (or that HP=20
> > 7 instructions) will open access to the share memory for them
> > regardless which CPU they are coming from. If other thread
> That still requires cross processor synchronization - so it will still
> take the same hit

It's actually an instruction on ia64, so the overhead is fairly low
(similar to a cache miss). That said, Linux doesn't have the ability
to share portions of page tables between processes at present, so it
doesn't matter.

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