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Option for host managed memory (#1400)
* Option for host managed memory * Rename Allocator to MemoryCreator * Create LinearMemory and MemoryCreator traits in api * Leave only one as_ptr function in LinearMemory trait * Memory creator test * Update comments/docs for LinearMemory and MemoryCreator traits * Add guard page to the custom memory example * Remove mut from LinearMemory trait as_ptr * Host_memory_grow test
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Maciej Kot
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Apr 6, 2020
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,192 @@ | ||
| #[cfg(not(target_os = "windows"))] | ||
| mod not_for_windows { | ||
| use wasmtime::*; | ||
| use wasmtime_environ::{WASM_MAX_PAGES, WASM_PAGE_SIZE}; | ||
|
|
||
| use libc::c_void; | ||
| use libc::MAP_FAILED; | ||
| use libc::{mmap, mprotect, munmap}; | ||
| use libc::{sysconf, _SC_PAGESIZE}; | ||
| use libc::{MAP_ANON, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE}; | ||
|
|
||
| use std::cell::RefCell; | ||
| use std::io::Error; | ||
| use std::ptr::null_mut; | ||
| use std::sync::{Arc, Mutex}; | ||
|
|
||
| struct CustomMemory { | ||
| mem: *mut c_void, | ||
| size: usize, | ||
| used_wasm_pages: RefCell<u32>, | ||
| glob_page_counter: Arc<Mutex<u64>>, | ||
| } | ||
|
|
||
| impl CustomMemory { | ||
| unsafe fn new( | ||
| num_wasm_pages: u32, | ||
| max_wasm_pages: u32, | ||
| glob_counter: Arc<Mutex<u64>>, | ||
| ) -> Self { | ||
| let page_size = sysconf(_SC_PAGESIZE) as usize; | ||
| let guard_size = page_size; | ||
| let size = max_wasm_pages as usize * WASM_PAGE_SIZE as usize + guard_size; | ||
| let used_size = num_wasm_pages as usize * WASM_PAGE_SIZE as usize; | ||
| assert_eq!(size % page_size, 0); // we rely on WASM_PAGE_SIZE being multiple of host page size | ||
|
|
||
| let mem = mmap(null_mut(), size, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0); | ||
| assert_ne!(mem, MAP_FAILED, "mmap failed: {}", Error::last_os_error()); | ||
|
|
||
| let r = mprotect(mem, used_size, PROT_READ | PROT_WRITE); | ||
| assert_eq!(r, 0, "mprotect failed: {}", Error::last_os_error()); | ||
| *glob_counter.lock().unwrap() += num_wasm_pages as u64; | ||
|
|
||
| Self { | ||
| mem, | ||
| size, | ||
| used_wasm_pages: RefCell::new(num_wasm_pages), | ||
| glob_page_counter: glob_counter, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl Drop for CustomMemory { | ||
| fn drop(&mut self) { | ||
| let n = *self.used_wasm_pages.borrow() as u64; | ||
| *self.glob_page_counter.lock().unwrap() -= n; | ||
| let r = unsafe { munmap(self.mem, self.size) }; | ||
| assert_eq!(r, 0, "munmap failed: {}", Error::last_os_error()); | ||
| } | ||
| } | ||
|
|
||
| unsafe impl LinearMemory for CustomMemory { | ||
| fn size(&self) -> u32 { | ||
| *self.used_wasm_pages.borrow() | ||
| } | ||
|
|
||
| fn grow(&self, delta: u32) -> Option<u32> { | ||
| let delta_size = (delta as usize).checked_mul(WASM_PAGE_SIZE as usize)?; | ||
|
|
||
| let prev_pages = *self.used_wasm_pages.borrow(); | ||
| let prev_size = (prev_pages as usize).checked_mul(WASM_PAGE_SIZE as usize)?; | ||
|
|
||
| let new_pages = prev_pages.checked_add(delta)?; | ||
| let new_size = (new_pages as usize).checked_mul(WASM_PAGE_SIZE as usize)?; | ||
|
|
||
| let guard_size = unsafe { sysconf(_SC_PAGESIZE) as usize }; | ||
|
|
||
| if new_size > self.size - guard_size { | ||
| return None; | ||
| } | ||
| unsafe { | ||
| let start = (self.mem as *mut u8).add(prev_size) as _; | ||
| let r = mprotect(start, delta_size, PROT_READ | PROT_WRITE); | ||
| assert_eq!(r, 0, "mprotect failed: {}", Error::last_os_error()); | ||
| } | ||
|
|
||
| *self.glob_page_counter.lock().unwrap() += delta as u64; | ||
| *self.used_wasm_pages.borrow_mut() = new_pages; | ||
| Some(prev_pages) | ||
| } | ||
|
|
||
| fn as_ptr(&self) -> *mut u8 { | ||
| self.mem as *mut u8 | ||
| } | ||
| } | ||
|
|
||
| struct CustomMemoryCreator { | ||
| pub num_created_memories: Mutex<usize>, | ||
| pub num_total_pages: Arc<Mutex<u64>>, | ||
| } | ||
|
|
||
| impl CustomMemoryCreator { | ||
| pub fn new() -> Self { | ||
| Self { | ||
| num_created_memories: Mutex::new(0), | ||
| num_total_pages: Arc::new(Mutex::new(0)), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| unsafe impl MemoryCreator for CustomMemoryCreator { | ||
| fn new_memory(&self, ty: MemoryType) -> Result<Box<dyn LinearMemory>, String> { | ||
| let max = ty.limits().max().unwrap_or(WASM_MAX_PAGES); | ||
| unsafe { | ||
| let mem = Box::new(CustomMemory::new( | ||
| ty.limits().min(), | ||
| max, | ||
| self.num_total_pages.clone(), | ||
| )); | ||
| *self.num_created_memories.lock().unwrap() += 1; | ||
| Ok(mem) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[test] | ||
| fn host_memory() -> anyhow::Result<()> { | ||
| let mem_creator = Arc::new(CustomMemoryCreator::new()); | ||
| let mut config = Config::default(); | ||
| config.with_host_memory(mem_creator.clone()); | ||
| let engine = Engine::new(&config); | ||
| let store = Store::new(&engine); | ||
|
|
||
| let module = Module::new( | ||
| &store, | ||
| r#" | ||
| (module | ||
| (memory (export "memory") 1) | ||
| ) | ||
| "#, | ||
| )?; | ||
| Instance::new(&module, &[])?; | ||
|
|
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| assert_eq!(*mem_creator.num_created_memories.lock().unwrap(), 1); | ||
|
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| Ok(()) | ||
| } | ||
|
|
||
| #[test] | ||
| fn host_memory_grow() -> anyhow::Result<()> { | ||
| let mem_creator = Arc::new(CustomMemoryCreator::new()); | ||
| let mut config = Config::default(); | ||
| config.with_host_memory(mem_creator.clone()); | ||
| let engine = Engine::new(&config); | ||
| let store = Store::new(&engine); | ||
|
|
||
| let module = Module::new( | ||
| &store, | ||
| r#" | ||
| (module | ||
| (func $f (drop (memory.grow (i32.const 1)))) | ||
| (memory (export "memory") 1 2) | ||
| (start $f) | ||
| ) | ||
| "#, | ||
| )?; | ||
|
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| let instance1 = Instance::new(&module, &[])?; | ||
| let instance2 = Instance::new(&module, &[])?; | ||
|
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| assert_eq!(*mem_creator.num_created_memories.lock().unwrap(), 2); | ||
|
|
||
| assert_eq!( | ||
| instance2 | ||
| .get_export("memory") | ||
| .unwrap() | ||
| .memory() | ||
| .unwrap() | ||
| .size(), | ||
| 2 | ||
| ); | ||
|
|
||
| // we take the lock outside the assert, so it won't get poisoned on assert failure | ||
| let tot_pages = *mem_creator.num_total_pages.lock().unwrap(); | ||
| assert_eq!(tot_pages, 4); | ||
|
|
||
| drop(instance1); | ||
| let tot_pages = *mem_creator.num_total_pages.lock().unwrap(); | ||
| assert_eq!(tot_pages, 2); | ||
|
|
||
| Ok(()) | ||
| } | ||
| } |
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