feat(mt): move LDM window wait policy into Rust

Move the MT reusable-input wait decision and lock/overlap/condition-wait
ordering into Rust through a small callback projection. C retains ownership
of the pthread synchronization objects, private LDM window, and diagnostics.
Add layout assertions and callback-order tests for enabled and disabled LDM.

Test Plan:
- ulimit -v 41943040; CARGO_BUILD_JOBS=1; cargo test --manifest-path rust/Cargo.toml
- ulimit -v 41943040; CARGO_BUILD_JOBS=1; cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
- ulimit -v 41943040; make -B -C programs -j1 zstd
- ulimit -v 41943040; make -C tests -j1 test-zstream ZSTREAM_TESTTIME=-T1s
This commit is contained in:
2026-07-19 19:41:35 +02:00
parent bd9ca5115d
commit 082c5a7dbe
2 changed files with 232 additions and 10 deletions
+68 -9
View File
@@ -368,6 +368,33 @@ void ZSTDMT_rust_serialStateGenSequences(
ZSTDMT_serialGenerateLdmFn generateLdm,
ZSTDMT_serialUpdateChecksumFn updateChecksum,
ZSTDMT_serialAdvanceFn advance);
typedef void (*ZSTDMT_waitForLdmLockFn)(void* opaque);
typedef int (*ZSTDMT_waitForLdmOverlapFn)(
void* opaque, void* bufferStart, size_t bufferCapacity);
typedef void (*ZSTDMT_waitForLdmWaitFn)(void* opaque);
typedef void (*ZSTDMT_waitForLdmUnlockFn)(void* opaque);
typedef struct {
void* callbackContext;
void* bufferStart;
size_t bufferCapacity;
int ldmEnabled;
ZSTDMT_waitForLdmLockFn lock;
ZSTDMT_waitForLdmOverlapFn overlaps;
ZSTDMT_waitForLdmWaitFn wait;
ZSTDMT_waitForLdmUnlockFn unlock;
} ZSTDMT_RustWaitForLdmState;
typedef char ZSTDMT_rust_wait_for_ldm_state_layout[
(offsetof(ZSTDMT_RustWaitForLdmState, callbackContext) == 0
&& offsetof(ZSTDMT_RustWaitForLdmState, bufferStart) == sizeof(void*)
&& offsetof(ZSTDMT_RustWaitForLdmState, bufferCapacity) == 2 * sizeof(void*)
&& offsetof(ZSTDMT_RustWaitForLdmState, ldmEnabled) == 3 * sizeof(void*)
&& offsetof(ZSTDMT_RustWaitForLdmState, lock) == 4 * sizeof(void*)
&& offsetof(ZSTDMT_RustWaitForLdmState, overlaps) == 5 * sizeof(void*)
&& offsetof(ZSTDMT_RustWaitForLdmState, wait) == 6 * sizeof(void*)
&& offsetof(ZSTDMT_RustWaitForLdmState, unlock) == 7 * sizeof(void*)
&& sizeof(ZSTDMT_RustWaitForLdmState) == 8 * sizeof(void*)) ? 1 : -1];
void ZSTDMT_rust_waitForLdmComplete(
const ZSTDMT_RustWaitForLdmState* state);
unsigned ZSTDMT_rust_computeTargetJobLog(unsigned windowLog, unsigned chainLog,
int strategy, int enableLdm);
@@ -2102,22 +2129,54 @@ static int ZSTDMT_doesOverlapWindow(Buffer buffer, ZSTD_window_t window)
window.lowLimit);
}
static void ZSTDMT_waitForLdmLock(void* opaque)
{
ZSTDMT_CCtx* const mtctx = (ZSTDMT_CCtx*)opaque;
ZSTD_PTHREAD_MUTEX_LOCK(&mtctx->serial.ldmWindowMutex);
}
static int ZSTDMT_waitForLdmOverlap(
void* opaque, void* bufferStart, size_t bufferCapacity)
{
ZSTDMT_CCtx* const mtctx = (ZSTDMT_CCtx*)opaque;
Buffer const buffer = { bufferStart, bufferCapacity };
return ZSTDMT_doesOverlapWindow(buffer, mtctx->serial.ldmWindow);
}
static void ZSTDMT_waitForLdmWait(void* opaque)
{
ZSTDMT_CCtx* const mtctx = (ZSTDMT_CCtx*)opaque;
DEBUGLOG(5, "Waiting for LDM to finish...");
ZSTD_pthread_cond_wait(&mtctx->serial.ldmWindowCond,
&mtctx->serial.ldmWindowMutex);
}
static void ZSTDMT_waitForLdmUnlock(void* opaque)
{
ZSTDMT_CCtx* const mtctx = (ZSTDMT_CCtx*)opaque;
DEBUGLOG(6, "Done waiting for LDM to finish");
ZSTD_pthread_mutex_unlock(&mtctx->serial.ldmWindowMutex);
}
static void ZSTDMT_waitForLdmComplete(ZSTDMT_CCtx* mtctx, Buffer buffer)
{
if (mtctx->params.ldmParams.enableLdm == ZSTD_ps_enable) {
ZSTD_pthread_mutex_t* mutex = &mtctx->serial.ldmWindowMutex;
int const ldmEnabled = mtctx->params.ldmParams.enableLdm == ZSTD_ps_enable;
ZSTDMT_RustWaitForLdmState state;
if (ldmEnabled) {
DEBUGLOG(5, "ZSTDMT_waitForLdmComplete");
DEBUGLOG(5, "source [0x%zx, 0x%zx)",
(size_t)buffer.start,
(size_t)buffer.start + buffer.capacity);
ZSTD_PTHREAD_MUTEX_LOCK(mutex);
while (ZSTDMT_doesOverlapWindow(buffer, mtctx->serial.ldmWindow)) {
DEBUGLOG(5, "Waiting for LDM to finish...");
ZSTD_pthread_cond_wait(&mtctx->serial.ldmWindowCond, mutex);
}
DEBUGLOG(6, "Done waiting for LDM to finish");
ZSTD_pthread_mutex_unlock(mutex);
}
state.callbackContext = mtctx;
state.bufferStart = buffer.start;
state.bufferCapacity = buffer.capacity;
state.ldmEnabled = ldmEnabled;
state.lock = ZSTDMT_waitForLdmLock;
state.overlaps = ZSTDMT_waitForLdmOverlap;
state.wait = ZSTDMT_waitForLdmWait;
state.unlock = ZSTDMT_waitForLdmUnlock;
ZSTDMT_rust_waitForLdmComplete(&state);
}
/**
+164 -1
View File
@@ -14,7 +14,7 @@
//! are Rust-owned. C retains ownership of private descriptor fields and
//! platform synchronization.
use std::mem::{self, MaybeUninit};
use std::mem::{self, offset_of, size_of, MaybeUninit};
use std::os::raw::{c_int, c_uint, c_void};
use std::ptr;
use std::sync::Mutex;
@@ -90,6 +90,74 @@ pub type ZSTDMT_serialGenerateLdmFn =
pub type ZSTDMT_serialUpdateChecksumFn = unsafe extern "C" fn(*mut c_void, *const c_void, usize);
pub type ZSTDMT_serialAdvanceFn = unsafe extern "C" fn(*mut c_void);
type ZSTDMT_waitForLdmLockFn = unsafe extern "C" fn(*mut c_void);
type ZSTDMT_waitForLdmOverlapFn = unsafe extern "C" fn(*mut c_void, *mut c_void, usize) -> c_int;
type ZSTDMT_waitForLdmWaitFn = unsafe extern "C" fn(*mut c_void);
type ZSTDMT_waitForLdmUnlockFn = unsafe extern "C" fn(*mut c_void);
/// Projection for the MT wait that protects reusable input against LDM use.
///
/// Rust owns the enabled branch and lock/overlap/wait ordering. C retains the
/// pthread mutex, condition variable, and private LDM window state.
#[repr(C)]
pub struct ZSTDMT_RustWaitForLdmState {
callback_context: *mut c_void,
buffer_start: *mut c_void,
buffer_capacity: usize,
ldm_enabled: c_int,
lock: Option<ZSTDMT_waitForLdmLockFn>,
overlaps: Option<ZSTDMT_waitForLdmOverlapFn>,
wait: Option<ZSTDMT_waitForLdmWaitFn>,
unlock: Option<ZSTDMT_waitForLdmUnlockFn>,
}
const _: () = {
assert!(size_of::<ZSTDMT_waitForLdmLockFn>() == size_of::<usize>());
assert!(size_of::<ZSTDMT_waitForLdmOverlapFn>() == size_of::<usize>());
assert!(size_of::<ZSTDMT_waitForLdmWaitFn>() == size_of::<usize>());
assert!(size_of::<ZSTDMT_waitForLdmUnlockFn>() == size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, callback_context) == 0);
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, buffer_start) == size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, buffer_capacity) == 2 * size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, ldm_enabled) == 3 * size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, lock) == 4 * size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, overlaps) == 5 * size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, wait) == 6 * size_of::<usize>());
assert!(offset_of!(ZSTDMT_RustWaitForLdmState, unlock) == 7 * size_of::<usize>());
assert!(size_of::<ZSTDMT_RustWaitForLdmState>() == size_of::<[usize; 8]>());
};
/// Wait until the reusable input range no longer overlaps the serial LDM
/// window, preserving the C synchronization state behind callbacks.
#[no_mangle]
pub unsafe extern "C" fn ZSTDMT_rust_waitForLdmComplete(state: *const ZSTDMT_RustWaitForLdmState) {
if state.is_null() {
return;
}
let state = unsafe { &*state };
if state.ldm_enabled == 0 || state.callback_context.is_null() {
return;
}
let (Some(lock), Some(overlaps), Some(wait), Some(unlock)) =
(state.lock, state.overlaps, state.wait, state.unlock)
else {
return;
};
unsafe {
lock(state.callback_context);
while overlaps(
state.callback_context,
state.buffer_start,
state.buffer_capacity,
) != 0
{
wait(state.callback_context);
}
unlock(state.callback_context);
}
}
/// Scalar inputs for the MT streaming initializer. The full parameter
/// object, dictionary handles, pools, buffers, and synchronization remain
/// private to C. Rust owns the order in which the C callbacks are invoked and
@@ -3171,6 +3239,101 @@ mod tests {
finished: Vec<usize>,
}
struct WaitForLdmTestContext {
events: Vec<&'static str>,
overlaps: Vec<bool>,
next_overlap: usize,
}
unsafe extern "C" fn wait_for_ldm_test_lock(context: *mut c_void) {
unsafe {
(*context.cast::<WaitForLdmTestContext>())
.events
.push("lock")
};
}
unsafe extern "C" fn wait_for_ldm_test_overlaps(
context: *mut c_void,
_buffer_start: *mut c_void,
_buffer_capacity: usize,
) -> c_int {
let context = unsafe { &mut *context.cast::<WaitForLdmTestContext>() };
context.events.push("overlap");
let overlaps = context
.overlaps
.get(context.next_overlap)
.copied()
.unwrap_or(false);
context.next_overlap += 1;
c_int::from(overlaps)
}
unsafe extern "C" fn wait_for_ldm_test_wait(context: *mut c_void) {
unsafe {
(*context.cast::<WaitForLdmTestContext>())
.events
.push("wait")
};
}
unsafe extern "C" fn wait_for_ldm_test_unlock(context: *mut c_void) {
unsafe {
(*context.cast::<WaitForLdmTestContext>())
.events
.push("unlock")
};
}
fn wait_for_ldm_test_state(
context: &mut WaitForLdmTestContext,
ldm_enabled: c_int,
) -> ZSTDMT_RustWaitForLdmState {
ZSTDMT_RustWaitForLdmState {
callback_context: context as *mut _ as *mut c_void,
buffer_start: ptr::null_mut(),
buffer_capacity: 8,
ldm_enabled,
lock: Some(wait_for_ldm_test_lock),
overlaps: Some(wait_for_ldm_test_overlaps),
wait: Some(wait_for_ldm_test_wait),
unlock: Some(wait_for_ldm_test_unlock),
}
}
#[test]
fn wait_for_ldm_runs_overlap_wait_loop_before_unlocking() {
let mut context = WaitForLdmTestContext {
events: Vec::new(),
overlaps: vec![true, false],
next_overlap: 0,
};
let state = wait_for_ldm_test_state(&mut context, ZSTD_PS_ENABLE);
unsafe { ZSTDMT_rust_waitForLdmComplete(&state) };
assert_eq!(
context.events,
vec!["lock", "overlap", "wait", "overlap", "unlock"]
);
assert_eq!(context.next_overlap, 2);
}
#[test]
fn wait_for_ldm_skips_callbacks_when_ldm_is_disabled() {
let mut context = WaitForLdmTestContext {
events: Vec::new(),
overlaps: vec![true],
next_overlap: 0,
};
let state = wait_for_ldm_test_state(&mut context, 0);
unsafe { ZSTDMT_rust_waitForLdmComplete(&state) };
assert!(context.events.is_empty());
assert_eq!(context.next_overlap, 0);
}
fn record_compression_job_event(state: &Rc<RefCell<MockCompressionJob>>, event: &'static str) {
state.borrow_mut().events.push(event);
}