Re: [PATCH][next] EDAC, pnd2: Make read-only const array intlv static

[Colin King (gmail)]

On 19/09/2024 08:19, Zhuo, Qiuxu wrote:
> > From: Colin Ian King <colin.i.king@xxxxxxxxx>
> > [...]
> > Subject: [PATCH][next] EDAC, pnd2: Make read-only const array intlv static
> >
> > Don't populate the const read-only array intlv on the stack at run time, instead
> > make it static.
> >
> > Signed-off-by: Colin Ian King <colin.i.king@xxxxxxxxx>
> > ---
> >   drivers/edac/pnd2_edac.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/edac/pnd2_edac.c b/drivers/edac/pnd2_edac.c index
> > f93f2f2b1cf2..af14c8a3279f 100644
> > --- a/drivers/edac/pnd2_edac.c
> > +++ b/drivers/edac/pnd2_edac.c
> > @@ -372,7 +372,7 @@ static int gen_asym_mask(struct
> > b_cr_slice_channel_hash *p,
> >   			 struct b_cr_asym_mem_region1_mchbar *as1,
> >   			 struct b_cr_asym_2way_mem_region_mchbar
> > *as2way)  {
> > -	const int intlv[] = { 0x5, 0xA, 0x3, 0xC };
> > +	static const int intlv[] = { 0x5, 0xA, 0x3, 0xC };
> >   	int mask = 0;
> >
> >   	if (as2way->asym_2way_interleave_enable)
> > @@ -489,7 +489,7 @@ static int dnv_get_registers(void)
> >    */
> >   static int get_registers(void)
> >   {
> > -	const int intlv[] = { 10, 11, 12, 12 };
> > +	static const int intlv[] = { 10, 11, 12, 12 };
>
> I didn't see the why and the benefits of these changes.
> Could you elaborate more?

The non-const construct will generate code to put the array on the stack 
and this occurs on each call, so there is a small amount of extra object 
code overhead to do this at run time. Making it static will put the data
into a data section so there is run-time penalty. So this change 
potentially shrinks the object code and run time overhead a very small 
amount.

Colin