circuitpython/docs/reference
Jim Mussared b326edf68c all: Remove MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE.
This commit removes all parts of code associated with the existing
MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE optimisation option, including the
-mcache-lookup-bc option to mpy-cross.

This feature originally provided a significant performance boost for Unix,
but wasn't able to be enabled for MCU targets (due to frozen bytecode), and
added significant extra complexity to generating and distributing .mpy
files.

The equivalent performance gain is now provided by the combination of
MICROPY_OPT_LOAD_ATTR_FAST_PATH and MICROPY_OPT_MAP_LOOKUP_CACHE (which has
been enabled on the unix port in the previous commit).

It's hard to provide precise performance numbers, but tests have been run
on a wide variety of architectures (x86-64, ARM Cortex, Aarch64, RISC-V,
xtensa) and they all generally agree on the qualitative improvements seen
by the combination of MICROPY_OPT_LOAD_ATTR_FAST_PATH and
MICROPY_OPT_MAP_LOOKUP_CACHE.

For example, on a "quiet" Linux x64 environment (i3-5010U @ 2.10GHz) the
change from CACHE_MAP_LOOKUP_IN_BYTECODE, to LOAD_ATTR_FAST_PATH combined
with MAP_LOOKUP_CACHE is:

diff of scores (higher is better)
N=2000 M=2000       bccache -> attrmapcache      diff      diff% (error%)
bm_chaos.py        13742.56 ->   13905.67 :   +163.11 =  +1.187% (+/-3.75%)
bm_fannkuch.py        60.13 ->      61.34 :     +1.21 =  +2.012% (+/-2.11%)
bm_fft.py         113083.20 ->  114793.68 :  +1710.48 =  +1.513% (+/-1.57%)
bm_float.py       256552.80 ->  243908.29 : -12644.51 =  -4.929% (+/-1.90%)
bm_hexiom.py         521.93 ->     625.41 :   +103.48 = +19.826% (+/-0.40%)
bm_nqueens.py     197544.25 ->  217713.12 : +20168.87 = +10.210% (+/-3.01%)
bm_pidigits.py      8072.98 ->    8198.75 :   +125.77 =  +1.558% (+/-3.22%)
misc_aes.py        17283.45 ->   16480.52 :   -802.93 =  -4.646% (+/-0.82%)
misc_mandel.py     99083.99 ->  128939.84 : +29855.85 = +30.132% (+/-5.88%)
misc_pystone.py    83860.10 ->   82592.56 :  -1267.54 =  -1.511% (+/-2.27%)
misc_raytrace.py   21490.40 ->   22227.23 :   +736.83 =  +3.429% (+/-1.88%)

This shows that the new optimisations are at least as good as the existing
inline-bytecode-caching, and are sometimes much better (because the new
ones apply caching to a wider variety of map lookups).

The new optimisations can also benefit code generated by the native
emitter, because they apply to the runtime rather than the generated code.
The improvement for the native emitter when LOAD_ATTR_FAST_PATH and
MAP_LOOKUP_CACHE are enabled is (same Linux environment as above):

diff of scores (higher is better)
N=2000 M=2000        native -> nat-attrmapcache  diff      diff% (error%)
bm_chaos.py        14130.62 ->   15464.68 :  +1334.06 =  +9.441% (+/-7.11%)
bm_fannkuch.py        74.96 ->      76.16 :     +1.20 =  +1.601% (+/-1.80%)
bm_fft.py         166682.99 ->  168221.86 :  +1538.87 =  +0.923% (+/-4.20%)
bm_float.py       233415.23 ->  265524.90 : +32109.67 = +13.756% (+/-2.57%)
bm_hexiom.py         628.59 ->     734.17 :   +105.58 = +16.796% (+/-1.39%)
bm_nqueens.py     225418.44 ->  232926.45 :  +7508.01 =  +3.331% (+/-3.10%)
bm_pidigits.py      6322.00 ->    6379.52 :    +57.52 =  +0.910% (+/-5.62%)
misc_aes.py        20670.10 ->   27223.18 :  +6553.08 = +31.703% (+/-1.56%)
misc_mandel.py    138221.11 ->  152014.01 : +13792.90 =  +9.979% (+/-2.46%)
misc_pystone.py    85032.14 ->  105681.44 : +20649.30 = +24.284% (+/-2.25%)
misc_raytrace.py   19800.01 ->   23350.73 :  +3550.72 = +17.933% (+/-2.79%)

In summary, compared to MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE, the new
MICROPY_OPT_LOAD_ATTR_FAST_PATH and MICROPY_OPT_MAP_LOOKUP_CACHE options:
- are simpler;
- take less code size;
- are faster (generally);
- work with code generated by the native emitter;
- can be used on embedded targets with a small and constant RAM overhead;
- allow the same .mpy bytecode to run on all targets.

See #7680 for further discussion.  And see also #7653 for a discussion
about simplifying mpy-cross options.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
2021-09-16 16:04:03 +10:00
..
asm_thumb2_arith.rst docs: Add reference for Thumb2 inline assembler. 2015-06-25 00:21:35 +01:00
asm_thumb2_compare.rst docs: Add reference for Thumb2 inline assembler. 2015-06-25 00:21:35 +01:00
asm_thumb2_directives.rst docs: More consistent capitalization and use of articles in headings. 2020-01-06 22:17:29 +11:00
asm_thumb2_float.rst docs: More consistent capitalization and use of articles in headings. 2020-01-06 22:17:29 +11:00
asm_thumb2_hints_tips.rst docs: Spelling mistakes 2016-08-02 11:17:46 +03:00
asm_thumb2_index.rst docs: More consistent capitalization and use of articles in headings. 2020-01-06 22:17:29 +11:00
asm_thumb2_label_branch.rst docs: Spelling mistakes 2016-08-02 11:17:46 +03:00
asm_thumb2_ldr.rst docs: Add reference for Thumb2 inline assembler. 2015-06-25 00:21:35 +01:00
asm_thumb2_logical_bit.rst docs: More consistent capitalization and use of articles in headings. 2020-01-06 22:17:29 +11:00
asm_thumb2_misc.rst docs: Several minor changes: network, pyb, ADCAll and inline asm. 2016-01-13 21:53:26 +00:00
asm_thumb2_mov.rst py/inlinethumb: Remove 30-bit restriction on movwt instruction. 2016-01-07 16:34:11 +00:00
asm_thumb2_stack.rst docs: Add reference for Thumb2 inline assembler. 2015-06-25 00:21:35 +01:00
asm_thumb2_str.rst docs: Add reference for Thumb2 inline assembler. 2015-06-25 00:21:35 +01:00
constrained.rst docs: Replace ufoo with foo in all docs. 2021-08-13 22:53:29 +10:00
filesystem.rst docs: Replace ufoo with foo in all docs. 2021-08-13 22:53:29 +10:00
glossary.rst docs: Replace ufoo with foo in all docs. 2021-08-13 22:53:29 +10:00
index.rst docs: More consistent capitalization and use of articles in headings. 2020-01-06 22:17:29 +11:00
isr_rules.rst docs/reference: Add note about multiple exceptions when heap is locked. 2020-06-02 15:56:34 +10:00
mpyfiles.rst all: Remove MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE. 2021-09-16 16:04:03 +10:00
packages.rst docs/library/index.rst: Clarify module naming and purpose. 2021-08-13 23:14:08 +10:00
pyboard.py.rst tools: Add filesystem action examples to pyboard.py help. 2021-02-13 14:37:28 +11:00
repl.rst docs/reference/repl.rst: Add information about new raw-paste mode. 2020-12-01 22:35:13 +11:00
speed_python.rst docs/reference: Mention that slicing a memoryview causes allocation. 2021-08-30 23:55:29 +10:00