Commit c332813b authored Dec 01, 2015 by Rasmus Villemoes Committed by Ingo Molnar Dec 04, 2015

x86/mm/mtrr: Mark the 'range_new' static variable in mtrr_calc_range_state() as __initdata



'range_new' doesn't seem to be used after init. It is only passed
to memset(), sum_ranges(), memcmp() and x86_get_mtrr_mem_range(), the
latter of which also only passes it on to various *range*
library functions.

So mark it __initdata to free up an extra page after init.

Its contents are wiped at every call to mtrr_calc_range_state(),
so it being static is not about preserving state between calls,
but simply to avoid a 4k+ stack frame. While there, add a
comment explaining this and why it's safe.

We could also mark nr_range_new as __initdata, but since it's
just a single int and also doesn't carry state between calls (it
is unconditionally assigned to before it is read), we might as
well make it an ordinary automatic variable.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Link: http://lkml.kernel.org/r/1449002691-20783-1-git-send-email-linux@rasmusvillemoes.dk


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 8609d1b5

arch/x86/kernel/cpu/mtrr/cleanup.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -593,9 +593,16 @@ mtrr_calc_range_state(u64 chunk_size, u64 gran_size,
		unsigned long x_remove_base,
		unsigned long x_remove_size, int i)
		{
		static struct range range_new[RANGE_NUM];
		/*
		* range_new should really be an automatic variable, but
		* putting 4096 bytes on the stack is frowned upon, to put it
		* mildly. It is safe to make it a static __initdata variable,
		* since mtrr_calc_range_state is only called during init and
		* there's no way it will call itself recursively.
		*/
		static struct range range_new[RANGE_NUM] __initdata;
		unsigned long range_sums_new;
		static int nr_range_new;
		int nr_range_new;
		int num_reg;

		/* Convert ranges to var ranges state: */