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SubjectRe: [PATCH 2/5] soc/fsl/qe: qe.c: reduce static memory footprint by 1.7K
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Le 30/04/2019 à 15:36, Rasmus Villemoes a écrit :
> The current array of struct qe_snum use 256*4 bytes for just keeping
> track of the free/used state of each index, and the struct layout
> means there's another 768 bytes of padding. If we just unzip that
> structure, the array of snum values just use 256 bytes, while the
> free/inuse state can be tracked in a 32 byte bitmap.
>
> So this reduces the .data footprint by 1760 bytes. It also serves as
> preparation for introducing another DT binding for specifying the snum
> values.
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> ---
> drivers/soc/fsl/qe/qe.c | 37 ++++++++++++-------------------------
> 1 file changed, 12 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c
> index 855373deb746..d0393f83145c 100644
> --- a/drivers/soc/fsl/qe/qe.c
> +++ b/drivers/soc/fsl/qe/qe.c
> @@ -14,6 +14,7 @@
> * Free Software Foundation; either version 2 of the License, or (at your
> * option) any later version.
> */
> +#include <linux/bitmap.h>
> #include <linux/errno.h>
> #include <linux/sched.h>
> #include <linux/kernel.h>
> @@ -43,25 +44,14 @@ static DEFINE_SPINLOCK(qe_lock);
> DEFINE_SPINLOCK(cmxgcr_lock);
> EXPORT_SYMBOL(cmxgcr_lock);
>
> -/* QE snum state */
> -enum qe_snum_state {
> - QE_SNUM_STATE_USED,
> - QE_SNUM_STATE_FREE
> -};
> -
> -/* QE snum */
> -struct qe_snum {
> - u8 num;
> - enum qe_snum_state state;
> -};
> -
> /* We allocate this here because it is used almost exclusively for
> * the communication processor devices.
> */
> struct qe_immap __iomem *qe_immr;
> EXPORT_SYMBOL(qe_immr);
>
> -static struct qe_snum snums[QE_NUM_OF_SNUM]; /* Dynamically allocated SNUMs */
> +static u8 snums[QE_NUM_OF_SNUM]; /* Dynamically allocated SNUMs */
> +static DECLARE_BITMAP(snum_state, QE_NUM_OF_SNUM);
> static unsigned int qe_num_of_snum;
>
> static phys_addr_t qebase = -1;
> @@ -308,6 +298,7 @@ static void qe_snums_init(void)
> };
> const u8 *snum_init;
>
> + bitmap_zero(snum_state, QE_NUM_OF_SNUM);

Doesn't make much importance, but wouldn't it be more logical to add
this line where the setting of .state = QE_SNUM_STATE_FREE was done
previously, ie around the for() loop below ?

> qe_num_of_snum = qe_get_num_of_snums();
>
> if (qe_num_of_snum == 76)
> @@ -315,10 +306,8 @@ static void qe_snums_init(void)
> else
> snum_init = snum_init_46;
>
> - for (i = 0; i < qe_num_of_snum; i++) {
> - snums[i].num = snum_init[i];
> - snums[i].state = QE_SNUM_STATE_FREE;
> - }
> + for (i = 0; i < qe_num_of_snum; i++)
> + snums[i] = snum_init[i];

Could use memcpy() instead ?

> }
>
> int qe_get_snum(void)
> @@ -328,12 +317,10 @@ int qe_get_snum(void)
> int i;
>
> spin_lock_irqsave(&qe_lock, flags);
> - for (i = 0; i < qe_num_of_snum; i++) {
> - if (snums[i].state == QE_SNUM_STATE_FREE) {
> - snums[i].state = QE_SNUM_STATE_USED;
> - snum = snums[i].num;
> - break;
> - }
> + i = find_first_zero_bit(snum_state, qe_num_of_snum);
> + if (i < qe_num_of_snum) {
> + set_bit(i, snum_state);
> + snum = snums[i];
> }
> spin_unlock_irqrestore(&qe_lock, flags);
>
> @@ -346,8 +333,8 @@ void qe_put_snum(u8 snum)
> int i;
>
> for (i = 0; i < qe_num_of_snum; i++) {
> - if (snums[i].num == snum) {
> - snums[i].state = QE_SNUM_STATE_FREE;
> + if (snums[i] == snum) {
> + clear_bit(i, snum_state);
> break;
> }
> }

Can we replace this loop by memchr() ?

Christophe

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