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

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'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 <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Toshi Kani <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Rasmus Villemoes 2015-12-01 21:44:50 +01:00 • committed by Ingo Molnar
commit c332813b51
1 changed files with 9 additions and 2 deletions
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11
arch/x86/kernel/cpu/mtrr/cleanup.c
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@ -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: */