runtime,syscall/js: reuse wasm memory DataView

Currently, every call to mem() incurs a new DataView object. This was necessary
because the wasm linear memory could grow at any time.

Now, whenever the memory grows, we make a call to the front-end. This allows us to
reuse the existing DataView object and create a new one only when the memory actually grows.

This gives us a boost in performance during DOM operations, while incurring an extra
trip to front-end when memory grows. However, since the GrowMemory calls are meant to decrease
over the runtime of an application, this is a good tradeoff in the long run.

The benchmarks have been tested inside a browser (Google Chrome 75.0.3770.90 (Official Build) (64-bit)).
It is hard to get stable nos. for DOM operations since the jumps make the timing very unreliable.
But overall, it shows a clear gain.

name  old time/op  new time/op  delta
DOM    135µs ±26%    84µs ±10%  -37.22%  (p=0.000 n=10+9)

Go1 benchmarks do not show any noticeable degradation:
name                   old time/op    new time/op    delta
BinaryTree17              22.5s ± 0%     22.5s ± 0%     ~     (p=0.743 n=8+9)
Fannkuch11                15.1s ± 0%     15.1s ± 0%   +0.17%  (p=0.000 n=9+9)
FmtFprintfEmpty           324ns ± 1%     303ns ± 0%   -6.64%  (p=0.000 n=9+10)
FmtFprintfString          535ns ± 1%     515ns ± 0%   -3.85%  (p=0.000 n=10+10)
FmtFprintfInt             609ns ± 0%     589ns ± 0%   -3.28%  (p=0.000 n=10+10)
FmtFprintfIntInt          938ns ± 0%     920ns ± 0%   -1.92%  (p=0.000 n=9+10)
FmtFprintfPrefixedInt     950ns ± 0%     924ns ± 0%   -2.72%  (p=0.000 n=10+9)
FmtFprintfFloat          1.41µs ± 1%    1.43µs ± 0%   +1.01%  (p=0.000 n=10+10)
FmtManyArgs              3.66µs ± 1%    3.46µs ± 0%   -5.43%  (p=0.000 n=9+10)
GobDecode                38.8ms ± 1%    37.8ms ± 0%   -2.50%  (p=0.000 n=10+8)
GobEncode                26.3ms ± 1%    26.3ms ± 0%     ~     (p=0.853 n=10+10)
Gzip                      1.16s ± 1%     1.16s ± 0%   -0.37%  (p=0.008 n=10+9)
Gunzip                    210ms ± 0%     208ms ± 1%   -1.01%  (p=0.000 n=10+10)
JSONEncode               48.0ms ± 0%    48.1ms ± 1%   +0.29%  (p=0.019 n=9+9)
JSONDecode                348ms ± 1%     326ms ± 1%   -6.34%  (p=0.000 n=10+10)
Mandelbrot200            6.62ms ± 0%    6.64ms ± 0%   +0.37%  (p=0.000 n=7+9)
GoParse                  23.9ms ± 1%    24.7ms ± 1%   +2.98%  (p=0.000 n=9+9)
RegexpMatchEasy0_32       555ns ± 0%     561ns ± 0%   +1.10%  (p=0.000 n=8+10)
RegexpMatchEasy0_1K      3.94µs ± 1%    3.94µs ± 0%     ~     (p=0.906 n=9+8)
RegexpMatchEasy1_32       516ns ± 0%     524ns ± 0%   +1.51%  (p=0.000 n=9+10)
RegexpMatchEasy1_1K      4.39µs ± 1%    4.40µs ± 1%     ~     (p=0.171 n=10+10)
RegexpMatchMedium_32     25.1ns ± 0%    25.5ns ± 0%   +1.51%  (p=0.000 n=9+8)
RegexpMatchMedium_1K      196µs ± 0%     203µs ± 1%   +3.23%  (p=0.000 n=9+10)
RegexpMatchHard_32       11.2µs ± 1%    11.6µs ± 1%   +3.62%  (p=0.000 n=10+10)
RegexpMatchHard_1K        334µs ± 1%     348µs ± 1%   +4.21%  (p=0.000 n=9+10)
Revcomp                   2.39s ± 0%     2.41s ± 0%   +0.78%  (p=0.000 n=8+9)
Template                  385ms ± 1%     336ms ± 0%  -12.61%  (p=0.000 n=10+9)
TimeParse                2.18µs ± 1%    2.18µs ± 1%     ~     (p=0.424 n=10+10)
TimeFormat               2.28µs ± 1%    2.22µs ± 1%   -2.30%  (p=0.000 n=10+10)

name                   old speed      new speed      delta
GobDecode              19.8MB/s ± 1%  20.3MB/s ± 0%   +2.56%  (p=0.000 n=10+8)
GobEncode              29.1MB/s ± 1%  29.2MB/s ± 0%     ~     (p=0.810 n=10+10)
Gzip                   16.7MB/s ± 1%  16.8MB/s ± 0%   +0.37%  (p=0.007 n=10+9)
Gunzip                 92.2MB/s ± 0%  93.2MB/s ± 1%   +1.03%  (p=0.000 n=10+10)
JSONEncode             40.4MB/s ± 0%  40.3MB/s ± 1%   -0.28%  (p=0.025 n=9+9)
JSONDecode             5.58MB/s ± 1%  5.96MB/s ± 1%   +6.80%  (p=0.000 n=10+10)
GoParse                2.42MB/s ± 0%  2.35MB/s ± 1%   -2.83%  (p=0.000 n=8+9)
RegexpMatchEasy0_32    57.7MB/s ± 0%  57.0MB/s ± 0%   -1.09%  (p=0.000 n=8+10)
RegexpMatchEasy0_1K     260MB/s ± 1%   260MB/s ± 0%     ~     (p=0.963 n=9+8)
RegexpMatchEasy1_32    62.1MB/s ± 0%  61.1MB/s ± 0%   -1.53%  (p=0.000 n=10+10)
RegexpMatchEasy1_1K     233MB/s ± 1%   233MB/s ± 1%     ~     (p=0.190 n=10+10)
RegexpMatchMedium_32   39.8MB/s ± 0%  39.1MB/s ± 1%   -1.74%  (p=0.000 n=9+10)
RegexpMatchMedium_1K   5.21MB/s ± 0%  5.05MB/s ± 1%   -3.09%  (p=0.000 n=9+10)
RegexpMatchHard_32     2.86MB/s ± 1%  2.76MB/s ± 1%   -3.43%  (p=0.000 n=10+10)
RegexpMatchHard_1K     3.06MB/s ± 1%  2.94MB/s ± 1%   -4.06%  (p=0.000 n=9+10)
Revcomp                 106MB/s ± 0%   105MB/s ± 0%   -0.77%  (p=0.000 n=8+9)
Template               5.04MB/s ± 1%  5.77MB/s ± 0%  +14.48%  (p=0.000 n=10+9)

Updates #32591

Change-Id: Id567e14a788e359248b2129ef1cf0adc8cc4ab7f
Reviewed-on: https://go-review.googlesource.com/c/go/+/183457
Run-TryBot: Agniva De Sarker <agniva.quicksilver@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Richard Musiol <neelance@gmail.com>

1 files changed, 45 insertions, 46 deletions

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index a54bb9a95d..7341e755e7 100644
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -113,24 +113,19 @@
 			this._scheduledTimeouts = new Map();
 			this._nextCallbackTimeoutID = 1;
 
-			const mem = () => {
-				// The buffer may change when requesting more memory.
-				return new DataView(this._inst.exports.mem.buffer);
-			}
-
 			const setInt64 = (addr, v) => {
-				mem().setUint32(addr + 0, v, true);
-				mem().setUint32(addr + 4, Math.floor(v / 4294967296), true);
+				this.mem.setUint32(addr + 0, v, true);
+				this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true);
 			}
 
 			const getInt64 = (addr) => {
-				const low = mem().getUint32(addr + 0, true);
-				const high = mem().getInt32(addr + 4, true);
+				const low = this.mem.getUint32(addr + 0, true);
+				const high = this.mem.getInt32(addr + 4, true);
 				return low + high * 4294967296;
 			}
 
 			const loadValue = (addr) => {
-				const f = mem().getFloat64(addr, true);
+				const f = this.mem.getFloat64(addr, true);
 				if (f === 0) {
 					return undefined;
 				}
@@ -138,7 +133,7 @@
 					return f;
 				}
 
-				const id = mem().getUint32(addr, true);
+				const id = this.mem.getUint32(addr, true);
 				return this._values[id];
 			}
 
@@ -147,34 +142,34 @@
 
 				if (typeof v === "number") {
 					if (isNaN(v)) {
-						mem().setUint32(addr + 4, nanHead, true);
-						mem().setUint32(addr, 0, true);
+						this.mem.setUint32(addr + 4, nanHead, true);
+						this.mem.setUint32(addr, 0, true);
 						return;
 					}
 					if (v === 0) {
-						mem().setUint32(addr + 4, nanHead, true);
-						mem().setUint32(addr, 1, true);
+						this.mem.setUint32(addr + 4, nanHead, true);
+						this.mem.setUint32(addr, 1, true);
 						return;
 					}
-					mem().setFloat64(addr, v, true);
+					this.mem.setFloat64(addr, v, true);
 					return;
 				}
 
 				switch (v) {
 					case undefined:
-						mem().setFloat64(addr, 0, true);
+						this.mem.setFloat64(addr, 0, true);
 						return;
 					case null:
-						mem().setUint32(addr + 4, nanHead, true);
-						mem().setUint32(addr, 2, true);
+						this.mem.setUint32(addr + 4, nanHead, true);
+						this.mem.setUint32(addr, 2, true);
 						return;
 					case true:
-						mem().setUint32(addr + 4, nanHead, true);
-						mem().setUint32(addr, 3, true);
+						this.mem.setUint32(addr + 4, nanHead, true);
+						this.mem.setUint32(addr, 3, true);
 						return;
 					case false:
-						mem().setUint32(addr + 4, nanHead, true);
-						mem().setUint32(addr, 4, true);
+						this.mem.setUint32(addr + 4, nanHead, true);
+						this.mem.setUint32(addr, 4, true);
 						return;
 				}
 
@@ -196,8 +191,8 @@
 						typeFlag = 3;
 						break;
 				}
-				mem().setUint32(addr + 4, nanHead | typeFlag, true);
-				mem().setUint32(addr, ref, true);
+				this.mem.setUint32(addr + 4, nanHead | typeFlag, true);
+				this.mem.setUint32(addr, ref, true);
 			}
 
 			const loadSlice = (addr) => {
@@ -232,7 +227,7 @@
 
 					// func wasmExit(code int32)
 					"runtime.wasmExit": (sp) => {
-						const code = mem().getInt32(sp + 8, true);
+						const code = this.mem.getInt32(sp + 8, true);
 						this.exited = true;
 						delete this._inst;
 						delete this._values;
@@ -244,10 +239,15 @@
 					"runtime.wasmWrite": (sp) => {
 						const fd = getInt64(sp + 8);
 						const p = getInt64(sp + 16);
-						const n = mem().getInt32(sp + 24, true);
+						const n = this.mem.getInt32(sp + 24, true);
 						fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
 					},
 
+					// func resetMemoryDataView()
+					"runtime.resetMemoryDataView": (sp) => {
+						this.mem = new DataView(this._inst.exports.mem.buffer);
+					},
+
 					// func nanotime() int64
 					"runtime.nanotime": (sp) => {
 						setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
@@ -257,7 +257,7 @@
 					"runtime.walltime": (sp) => {
 						const msec = (new Date).getTime();
 						setInt64(sp + 8, msec / 1000);
-						mem().setInt32(sp + 16, (msec % 1000) * 1000000, true);
+						this.mem.setInt32(sp + 16, (msec % 1000) * 1000000, true);
 					},
 
 					// func scheduleTimeoutEvent(delay int64) int32
@@ -276,12 +276,12 @@
 							},
 							getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
 						));
-						mem().setInt32(sp + 16, id, true);
+						this.mem.setInt32(sp + 16, id, true);
 					},
 
 					// func clearTimeoutEvent(id int32)
 					"runtime.clearTimeoutEvent": (sp) => {
-						const id = mem().getInt32(sp + 8, true);
+						const id = this.mem.getInt32(sp + 8, true);
 						clearTimeout(this._scheduledTimeouts.get(id));
 						this._scheduledTimeouts.delete(id);
 					},
@@ -327,10 +327,10 @@
 							const result = Reflect.apply(m, v, args);
 							sp = this._inst.exports.getsp(); // see comment above
 							storeValue(sp + 56, result);
-							mem().setUint8(sp + 64, 1);
+							this.mem.setUint8(sp + 64, 1);
 						} catch (err) {
 							storeValue(sp + 56, err);
-							mem().setUint8(sp + 64, 0);
+							this.mem.setUint8(sp + 64, 0);
 						}
 					},
 
@@ -342,10 +342,10 @@
 							const result = Reflect.apply(v, undefined, args);
 							sp = this._inst.exports.getsp(); // see comment above
 							storeValue(sp + 40, result);
-							mem().setUint8(sp + 48, 1);
+							this.mem.setUint8(sp + 48, 1);
 						} catch (err) {
 							storeValue(sp + 40, err);
-							mem().setUint8(sp + 48, 0);
+							this.mem.setUint8(sp + 48, 0);
 						}
 					},
 
@@ -357,10 +357,10 @@
 							const result = Reflect.construct(v, args);
 							sp = this._inst.exports.getsp(); // see comment above
 							storeValue(sp + 40, result);
-							mem().setUint8(sp + 48, 1);
+							this.mem.setUint8(sp + 48, 1);
 						} catch (err) {
 							storeValue(sp + 40, err);
-							mem().setUint8(sp + 48, 0);
+							this.mem.setUint8(sp + 48, 0);
 						}
 					},
 
@@ -384,7 +384,7 @@
 
 					// func valueInstanceOf(v ref, t ref) bool
 					"syscall/js.valueInstanceOf": (sp) => {
-						mem().setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
+						this.mem.setUint8(sp + 24, loadValue(sp + 8) instanceof loadValue(sp + 16));
 					},
 
 					// func copyBytesToGo(dst []byte, src ref) (int, bool)
@@ -392,13 +392,13 @@
 						const dst = loadSlice(sp + 8);
 						const src = loadValue(sp + 32);
 						if (!(src instanceof Uint8Array)) {
-							mem().setUint8(sp + 48, 0);
+							this.mem.setUint8(sp + 48, 0);
 							return;
 						}
 						const toCopy = src.subarray(0, dst.length);
 						dst.set(toCopy);
 						setInt64(sp + 40, toCopy.length);
-						mem().setUint8(sp + 48, 1);
+						this.mem.setUint8(sp + 48, 1);
 					},
 
 					// func copyBytesToJS(dst ref, src []byte) (int, bool)
@@ -406,13 +406,13 @@
 						const dst = loadValue(sp + 8);
 						const src = loadSlice(sp + 16);
 						if (!(dst instanceof Uint8Array)) {
-							mem().setUint8(sp + 48, 0);
+							this.mem.setUint8(sp + 48, 0);
 							return;
 						}
 						const toCopy = src.subarray(0, dst.length);
 						dst.set(toCopy);
 						setInt64(sp + 40, toCopy.length);
-						mem().setUint8(sp + 48, 1);
+						this.mem.setUint8(sp + 48, 1);
 					},
 
 					"debug": (value) => {
@@ -424,6 +424,7 @@
 
 		async run(instance) {
 			this._inst = instance;
+			this.mem = new DataView(this._inst.exports.mem.buffer);
 			this._values = [ // TODO: garbage collection
 				NaN,
 				0,
@@ -436,15 +437,13 @@
 			this._refs = new Map();
 			this.exited = false;
 
-			const mem = new DataView(this._inst.exports.mem.buffer)
-
 			// Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
 			let offset = 4096;
 
 			const strPtr = (str) => {
 				const ptr = offset;
 				const bytes = encoder.encode(str + "\0");
-				new Uint8Array(mem.buffer, offset, bytes.length).set(bytes);
+				new Uint8Array(this.mem.buffer, offset, bytes.length).set(bytes);
 				offset += bytes.length;
 				if (offset % 8 !== 0) {
 					offset += 8 - (offset % 8);
@@ -467,8 +466,8 @@
 
 			const argv = offset;
 			argvPtrs.forEach((ptr) => {
-				mem.setUint32(offset, ptr, true);
-				mem.setUint32(offset + 4, 0, true);
+				this.mem.setUint32(offset, ptr, true);
+				this.mem.setUint32(offset + 4, 0, true);
 				offset += 8;
 			});