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Diffstat (limited to 'Notes.md')
| -rw-r--r-- | Notes.md | 30 |
1 files changed, 29 insertions, 1 deletions
@@ -147,6 +147,34 @@ Overall, using this approach, we don't need a trampoline (`run`). We reduce the The `examples/lockopt.rs` shows that locks are effectively optimized out. +Old Implementation +``` asm +00000130 <GPIOB>: + 130: 21a0 movs r1, #160 ; 0xa0 + 132: f3ef 8011 mrs r0, BASEPRI + 136: f381 8811 msr BASEPRI, r1 + 13a: f240 0100 movw r1, #0 + 13e: f2c2 0100 movt r1, #8192 ; 0x2000 + 142: 680a ldr r2, [r1, #0] + 144: 3201 adds r2, #1 + 146: 600a str r2, [r1, #0] + 148: 21c0 movs r1, #192 ; 0xc0 + 14a: f381 8811 msr BASEPRI, r1 + 14e: f380 8811 msr BASEPRI, r0 + 152: 4770 bx lr + +00000154 <GPIOC>: + 154: f240 0100 movw r1, #0 + 158: f3ef 8011 mrs r0, BASEPRI + 15c: f2c2 0100 movt r1, #8192 ; 0x2000 + 160: 680a ldr r2, [r1, #0] + 162: 3202 adds r2, #2 + 164: 600a str r2, [r1, #0] + 166: f380 8811 msr BASEPRI, r0 + 16a: 4770 bx lr +``` + +With lock opt. We see a 20% improvement for short/small tasks. ``` asm 00000128 <GPIOB>: 128: 21a0 movs r1, #160 ; 0xa0 @@ -169,7 +197,7 @@ The `examples/lockopt.rs` shows that locks are effectively optimized out. 154: 4770 bx lr ``` -GPIOB/C are sharing a resource (C higher prio). Notice, there is no BASEPRI manipulation at all. +GPIOB/C are sharing a resource (C higher prio). Notice, for GPIOC there is no BASEPRI manipulation at all. For GPIOB, there is a single read of BASEPRI (stored in `old_basepri_hw`) and just two writes, one for entering critical section, one for exiting. On exit we detect that we are indeed at the initial priority for the task, thus we restore the `old_basepri_hw` instead of a logic priority. |