Changeset c5a98f3

Timestamp:

Dec 17, 2020, 4:18:15 PM (4 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, arm-eh, ast-experimental, enum, forall-pointer-decay, jacob/cs343-translation, master, new-ast-unique-expr, pthread-emulation, qualifiedEnum

Children:

41cde266

Parents:

aa1d13c

Message:

Clean-up and comments

File:

• benchmark/readyQ/locality.go (modified) (15 diffs)

benchmark/readyQ/locality.go

@@ -53 +53 @@
 }
 
-func NewCtx( sem * semaphore.Weighted, data * MyData, id int ) (MyCtx) {
-        return MyCtx{sem, unsafe.Pointer(data), context.Background(), syscall.Gettid(), id}
+func NewCtx( data * MyData, id int ) (MyCtx) {
+        r := MyCtx{semaphore.NewWeighted(1), unsafe.Pointer(data), context.Background(), syscall.Gettid(), id}
+        r.s.Acquire(context.Background(), 1)
+        return r
 }
 
@@ -66 +68 @@
 
 // ==================================================
+// Atomic object where a single thread can wait
+// May exchanges data
 type Spot struct {
-        ptr uintptr
-        id int
+        ptr uintptr // atomic variable use fo MES
+        id int      // id for debugging
 }
 
@@ -78 +82 @@
         new := uintptr(unsafe.Pointer(ctx))
         // old_d := ctx.d
+
+        // Attempt to CAS our context into the seat
         var raw uintptr
         for true {
                 raw = this.ptr
-                if raw == uintptr(1) {
+                if raw == uintptr(1) { // Seat is closed, return
                         return nil, true
                 }
                 if atomic.CompareAndSwapUintptr(&this.ptr, raw, new) {
-                        break
+                        break // We got the seat
                 }
         }
 
+        // If we aren't the fist in, wake someone
         if raw != uintptr(0) {
                 var val *MyCtx
                 val = (*MyCtx)(unsafe.Pointer(raw))
+
+                // If we are sharing, give them our data
                 if share {
                         // fmt.Printf("[%d] - %d update %d: %p -> %p\n", this.id, ctx.id, val.id, val.d, data)
@@ -97 +106 @@
                 }
 
+                // Wake them up
                 // fmt.Printf("[%d] - %d release %d\n", this.id, ctx.id, val.id)
                 val.s.Release(1)
@@ -102 +112 @@
 
         // fmt.Printf("[%d] - %d enter\n", this.id, ctx.id)
+
+        // Block once on the seat
         ctx.s.Acquire(ctx.c, 1)
+
+        // Someone woke us up, get the new data
         ret := (* MyData)(atomic.LoadPointer(&ctx.d))
         // fmt.Printf("[%d] - %d leave: %p -> %p\n", this.id, ctx.id, ret, old_d)
@@ -109 +123 @@
 }
 
+// Shutdown the spot
+// Wake current thread and mark seat as closed
 func (this * Spot) release() {
         val := (*MyCtx)(unsafe.Pointer(atomic.SwapUintptr(&this.ptr, uintptr(1))))
@@ -115 +131 @@
         }
 
+        // Someone was there, release them
         val.s.Release(1)
 }
 
 // ==================================================
+// Struct for result, Go doesn't support passing tuple in channels
 type Result struct {
         count uint64
@@ -130 +148 @@
 
 // ==================================================
+// Random number generator, Go's native one is to slow and global
 func __xorshift64( state * uint64 ) (uint64) {
         x := *state
@@ -139 +158 @@
 }
 
+// ==================================================
+// Do some work by accessing 'cnt' cells in the array
 func work(data * MyData, cnt uint64, state * uint64) {
         for i := uint64(0); i < cnt; i++ {
@@ -145 +166 @@
 }
 
+// Main body of the threads
 func local(result chan Result, start chan struct{}, size uint64, cnt uint64, channels [] Spot, share bool, id int) {
-        state := rand.Uint64()
-
-        data := NewData(id, size)
-        sem := semaphore.NewWeighted(1)
-        sem.Acquire(context.Background(), 1)
-        ctx := NewCtx(sem, data, id)
-
+        // Initialize some data
+        state := rand.Uint64()    // RNG state
+        data := NewData(id, size) // Starting piece of data
+        ctx := NewCtx(data, id)   // Goroutine local context
+
+        // Prepare results
         r := NewResult()
+
+        // Wait for start
         <- start
+
+        // Main loop
         for true {
+                // Touch our current data, write to invalidate remote cache lines
                 work(data, cnt, &state)
 
+                // Wait on a random spot
                 i := __xorshift64(&state) % uint64(len(channels))
                 var closed bool
                 data, closed = channels[i].put(&ctx, data, share)
 
-                if closed { break }
-                if  clock_mode && atomic.LoadInt32(&stop) == 1 { break }
-                if !clock_mode && r.count >= stop_count { break }
-                if uint64(len(data.data)) != size {
-                        panic("Data has weird size")
-                }
-
+                // Check if the experiment is over
+                if closed { break }                                       // yes, spot was closed
+                if  clock_mode && atomic.LoadInt32(&stop) == 1 { break }  // yes, time's up
+                if !clock_mode && r.count >= stop_count { break }         // yes, iterations reached
+
+                // Check everything is consistent
+                if uint64(len(data.data)) != size { panic("Data has weird size") }
+
+                // write down progress and check migrations
                 ttid := syscall.Gettid()
                 r.count += 1
@@ -175 +204 @@
         }
 
+        // Mark goroutine as done
         atomic.AddInt64(&threads_left, -1);
+
+        // return result
         result <- r
 }
 
+// ==================================================
+// Program main
 func main() {
+        // Benchmark specific command line arguments
         work_sizeOpt := flag.Uint64("w", 2    , "Number of words (uint64) per threads")
         countOpt     := flag.Uint64("c", 2    , "Number of words (uint64) to touch")
         shareOpt     := flag.Bool  ("s", false, "Pass the work data to the next thread when blocking")
 
+        // General benchmark initialization and deinitialization
         defer bench_init()()
 
+        // Eval command line arguments
         size  := *work_sizeOpt
         cnt   := *countOpt
         share := *shareOpt
 
+        // Check params
         if ! (nthreads > nprocs) {
                 fmt.Fprintf(os.Stderr, "Must have more threads than procs\n")
@@ -195 +233 @@
         }
 
-        barrierStart := make(chan struct{})
-        threads_left = int64(nprocs)
-        result  := make(chan Result)
-        channels := make([]Spot, nthreads - nprocs)
+        // Make global data
+        barrierStart := make(chan struct{})         // Barrier used at the start
+        threads_left = int64(nprocs)                // Counter for active threads (not 'nthreads' because at all times 'nthreads - nprocs' are blocked)
+        result  := make(chan Result)                // Channel for results
+        channels := make([]Spot, nthreads - nprocs) // Number of spots
         for i := range channels {
-                channels[i] = Spot{uintptr(0), i}
-        }
-
+                channels[i] = Spot{uintptr(0), i}     // init spots
+        }
+
+        // start the goroutines
         for i := 0; i < nthreads; i++ {
                 go local(result, barrierStart, size, cnt, channels, share, i)
@@ -210 +250 @@
         atomic.StoreInt32(&stop, 0)
         start := time.Now()
-        close(barrierStart)
-
-        wait(start, true);
+        close(barrierStart) // release barrier
+
+        wait(start, true);  // general benchmark wait
 
         atomic.StoreInt32(&stop, 1)
@@ -220 +260 @@
         fmt.Printf("\nDone\n")
 
+        // release all the blocked threads
         for i := range channels {
                 channels[i].release()
         }
 
+        // Join and accumulate results
         global_result := NewResult()
         for i := 0; i < nthreads; i++ {
@@ -232 +274 @@
         }
 
+        // Print with nice 's, i.e. 1'000'000 instead of 1000000
         p := message.NewPrinter(language.English)
         p.Printf("Duration (ms)          : %f\n", delta.Seconds());