gnh1201/wasm-micro-runtime
1
0
Fork 0
mirror of https://github.com/bytecodealliance/wasm-micro-runtime.git synced 2024-11-26 15:32:05 +00:00
Code Issues Actions 14 Packages Projects Releases Wiki Activity

doc/memory_tune.md: "remove malloc" hack is not relevant to wasi-threads (#2603)

Browse Source
This commit is contained in:
YAMAMOTO Takashi 2023-09-28 10:27:33 +09:00 committed by GitHub
parent cd0cec5beb
commit ac6435884f
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 1 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
doc/memory_tune.md
View File

@ -16,7 +16,7 @@ Note:
- **linear memory**: a contiguous, mutable array of raw bytes. It is created with an initial size but might be grown dynamically. For most compilers, e.g. wasi-sdk, emsdk, rustc or asc, normally it includes three parts, data area, auxiliary stack area and heap area. For wasi-sdk, the initial/max size can be specified with `-Wl,--initial-memory=n1,--max-memory=n2`, for emsdk, the initial/max size can be specified with `-s INITIAL_MEMORY=n1 -s MAXIMUM_MEMORY=n2 -s ALLOW_MEMORY_GROWTH=1` or `-s TOTAL_MEMORY=n`, and for asc, they can be specified with `--initialMemory` and `--maximumMemory` flags.
- If the memory access boundary check with hardware trap feature is enabled, e.g. in Linux/MacOS/Windows x86-64 by default, the linear memory is allocated by `os_mmap` from virtual address space instead of global heap.
- **aux stack**: the auxiliary stack resides in linear memory to store some temporary data when calling wasm functions, for example, calling a wasm function with complex struct arguments. For wasi-sdk, the size can be specified with `-z stack-size=n`, for emsdk, the size can be specified with `-s TOTAL_STACK=n`.
- **app heap and libc heap**: the heap to allocate memory for wasm app, note that app heap is created only when the malloc/free functions (or __new/__release functions for AssemblyScript) are not exported and runtime can not detect the libc heap. To export the malloc/free functions, for wasi-sdk and emsdk, developer can use `-Wl,--export=malloc -Wl,--export=free` options, for asc, developer can use `--exportRuntime` option. For app heap, the size is specified by `wasm_runtime_instantiate`. It is recommended to export the malloc/free functions and disable app heap in single thread mode, and for multi-threading, as the libc heap isn't thread-safe, it is recommended to remove the dlmalloc.o from libc.a for wasi-sdk and use `-s MALLOC="none"` for emsdk, refer to [WAMR pthread library](./pthread_library.md) for more details. And developer can use `wasm_runtime_module_malloc/wasm_runtime_module_free` to allocate/free memory from/to app heap (or libc heap if malloc/free functions are exported).
- **app heap and libc heap**: the heap to allocate memory for wasm app, note that app heap is created only when the malloc/free functions (or __new/__release functions for AssemblyScript) are not exported and runtime can not detect the libc heap. To export the malloc/free functions, for wasi-sdk and emsdk, developer can use `-Wl,--export=malloc -Wl,--export=free` options, for asc, developer can use `--exportRuntime` option. For app heap, the size is specified by `wasm_runtime_instantiate`. It is recommended to export the malloc/free functions and disable app heap. However, if you are using [the old pthread implementation](./pthread_impls.md), you might need some workaround to avoid the libc heap as mentioned in [WAMR pthread library](./pthread_library.md). And developer can use `wasm_runtime_module_malloc/wasm_runtime_module_free` to allocate/free memory from/to app heap (or libc heap if malloc/free functions are exported).
- **__data_end global and __heap_base global**: two globals exported by wasm application to indicate the end of data area and the base address of libc heap. For WAMR, it is recommended to export them as when there are no possible memory grow operations, runtime will truncate the linear memory into the size indicated by `__heap_base`, so as to reduce the footprint, or at least one page (64KB) is required by linear memory.
## Tune the memory usage