x86/ioperm: Share I/O bitmap if identical

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The I/O bitmap is duplicated on fork. That's wasting memory and slows down
fork. There is no point to do so. As long as the bitmap is not modified it
can be shared between threads and processes.

Add a refcount and just share it on fork. If a task modifies the bitmap
then it has to do the duplication if and only if it is shared.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>

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This commit is contained in:

Thomas Gleixner 2019-11-11 23:03:25 +01:00

parent ea5f1cd7ab

commit 4804e382c1

3 changed files with 50 additions and 42 deletions

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5

arch/x86/include/asm/io_bitmap.h

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48

arch/x86/kernel/ioport.c

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39

arch/x86/kernel/process.c

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