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| author | Jaremy Creechley <creechley@gmail.com> | 2021-11-16 11:30:07 -0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2021-11-16 20:30:07 +0100 |
| commit | 92d6fb86c66ceda154972314ba695cea4aac9301 (patch) | |
| tree | 9ecfc5922972e4818b35667e59e7c30e41c44f74 | |
| parent | 309ec7167e6ea17112901533539be0a1884c8b65 (diff) | |
| download | Nim-92d6fb86c66ceda154972314ba695cea4aac9301.tar.gz | |
Enable customizing PageShift to set PageSize for embedded targets (#19129)
* Enable customizing PageSize (via PageShift). This enables adjusting PageSize for embedded targets without abusing cpu16. * copy nimPageXYZ settings for mmpaptest * add docs for Nim manual * add docs for Nim manual * docs tweaks Co-authored-by: Jaremy Creechley <jaremy.creechley@panthalassa.com>
| -rw-r--r-- | doc/nimc.rst | 24 | ||||
| -rw-r--r-- | lib/system/bitmasks.nim | 10 | ||||
| -rw-r--r-- | tests/mmaptest.nim | 7 |
3 files changed, 36 insertions, 5 deletions
diff --git a/doc/nimc.rst b/doc/nimc.rst index 98b754729..d35dad6c2 100644 --- a/doc/nimc.rst +++ b/doc/nimc.rst @@ -656,6 +656,30 @@ is not available but C's `malloc` is. You can use the `nimAllocPagesViaMalloc` define to use `malloc` instead of `mmap`. `nimAllocPagesViaMalloc` is currently only supported with `--gc:arc` or `--gc:orc`. (Since version 1.6) +nimPage256 / nimPage512 / nimPage1k +=================================== + +Adjust the page size for Nim's GC allocator. This enables using +`nimAllocPagesViaMalloc` on devices with less RAM. The default +page size requires too much RAM to work. + +Recommended settings: + +- < 32 kB of RAM use `nimPage256` + +- < 512 kB of RAM use `nimPage512` + +- < 2 MB of RAM use `nimPage1k` + +Initial testing hasn't shown much difference between 512B or 1kB page sizes +in terms of performance or latency. Using `nimPages256` will limit the +total amount of allocatable RAM. + +nimMemAlignTiny +=============== + +Sets `MemAlign` to `4` bytes which reduces the memory alignment +to better match some embedded devices. Nim for realtime systems ======================== diff --git a/lib/system/bitmasks.nim b/lib/system/bitmasks.nim index caf86568a..9cb57bc45 100644 --- a/lib/system/bitmasks.nim +++ b/lib/system/bitmasks.nim @@ -10,14 +10,18 @@ # Page size of the system; in most cases 4096 bytes. For exotic OS or # CPU this needs to be changed: const - PageShift = when defined(cpu16): 8 else: 12 # \ - # my tests showed no improvements for using larger page sizes. + PageShift = when defined(nimPage256) or defined(cpu16): 8 + elif defined(nimPage512): 9 + elif defined(nimPage1k): 10 + else: 12 # \ # my tests showed no improvements for using larger page sizes. + PageSize = 1 shl PageShift PageMask = PageSize-1 MemAlign = # also minimal allocatable memory block - when defined(useMalloc): + when defined(nimMemAlignTiny): 4 + elif defined(useMalloc): when defined(amd64): 16 else: 8 else: 16 diff --git a/tests/mmaptest.nim b/tests/mmaptest.nim index 7a93cdd45..33010606f 100644 --- a/tests/mmaptest.nim +++ b/tests/mmaptest.nim @@ -19,8 +19,11 @@ proc `+!!`(p: pointer, size: int): pointer {.inline.} = result = cast[pointer](cast[int](p) + size) const - PageShift = when defined(cpu16): 8 else: 12 # \ - # my tests showed no improvements for using larger page sizes. + PageShift = when defined(nimPage256) or defined(cpu16): 8 + elif defined(nimPage512): 9 + elif defined(nimPage1k): 10 + else: 12 # \ # my tests showed no improvements for using larger page sizes. + PageSize = 1 shl PageShift var p = osAllocPages(3 * PageSize) |