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Subject[PATCH v2] x86, mtrr: mark range_new in mtrr_calc_range_state() as __initdata
Date
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>
---
Something like this, perhaps?

v2: Add comment on range_new, per Ingo.

arch/x86/kernel/cpu/mtrr/cleanup.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
index 70d7c93f4550..0d98503c2245 100644
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -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: */
--
2.6.1


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