Cut the speedtest1 runtime of the OPFS VFS proxy by approximately 3/4ths via xRead/xWrite buffer-copying optimizations. Still slower than the WASMFS impl by approx. 1/5th.

FossilOrigin-Name: fb7f287310d74a3e236125ae9c49b859f9263c29ae85161c1bcf9dd0778d8a51

1 files changed, 8 insertions, 0 deletions

diff --git a/ext/wasm/common/whwasmutil.js b/ext/wasm/common/whwasmutil.js
index 42f602d00..46cdf84bb 100644
--- a/ext/wasm/common/whwasmutil.js
+++ b/ext/wasm/common/whwasmutil.js
@@ -603,6 +603,10 @@ self.WhWasmUtilInstaller = function(target){
      out) the pointer's value, else it will contain an essentially
      random value.
 
+     ACHTUNG: calling this often, e.g. in a loop, can have a noticably
+     painful impact on performance. Rather than doing so, use
+     heapForSize() to fetch the heap object and read directly from it.
+
      See: setMemValue()
   */
   target.getMemValue = function(ptr, type='i8'){
@@ -633,6 +637,10 @@ self.WhWasmUtilInstaller = function(target){
      this function behaves as if the 3rd argument were `i32`.
 
      This function returns itself.
+
+     ACHTUNG: calling this often, e.g. in a loop, can have a noticably
+     painful impact on performance. Rather than doing so, use
+     heapForSize() to fetch the heap object and assign directly to it.
   */
   target.setMemValue = function f(ptr, value, type='i8'){
     if (type.endsWith('*')) type = ptrIR;