On Tue, 17 Nov 1998 05:48:43 +0100, Andi Kleen <ak@muc.de> said:
> If the threads share VM (with CLONE_VM) they share all memory,
> including the environment. argv[] is stored in the environment.
> Changing Linux to support only partly shared memory in CLONE_VM (with
> threads private pages like in Windows or OS/2) would be a fairly major
> redesign of the kernel threads mechanism.
Not to mention that the performance would suck: currently we avoid any
flushing of the hardware task context when we switch between threads.
That would not be possible if the threads maintained their own page
tables.
The best suggestion I've heard was to use the %fs register to maintain
a user-space pointer to thread-local storage. However, any access to
that space would be closely reliant on gcc extensions.
--Stephen
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