Add an experimental OPFS VFS-specific URI flag, opfs-unlock-asap, which tells the VFS to release implicit locks ASAP. This permits higher concurrency but hurts performance considerably. This may or may not be obsoleted by other concurrency-related experimentation.

FossilOrigin-Name: d23c917013485ec2793125221f3936b05c39d6eca941629fb819b6b4aa714520

1 files changed, 26 insertions, 1 deletions

diff --git a/ext/wasm/api/sqlite3-api-opfs.js b/ext/wasm/api/sqlite3-api-opfs.js
index 53f68a1d5..deb8bf04e 100644
--- a/ext/wasm/api/sqlite3-api-opfs.js
+++ b/ext/wasm/api/sqlite3-api-opfs.js
@@ -355,6 +355,25 @@ const installOpfsVfs = function callee(options){
         toss("Maintenance required: not found:",k);
       }
     });
+    state.opfsFlags = Object.assign(Object.create(null),{
+      /**
+         Flag for use with xOpen(). "opfs-unlock-asap=1" enables
+         this. See defaultUnlockAsap, below.
+       */
+      OPFS_UNLOCK_ASAP: 0x01,
+      /**
+         If true, any async routine which implicitly acquires a sync
+         access handle (i.e. an OPFS lock) will release that locks at
+         the end of the call which acquires it. If false, such
+         "autolocks" are not released until the VFS is idle for some
+         brief amount of time.
+
+         The benefit of enabling this is much higher concurrency. The
+         down-side is much-reduced performance (as much as a 4x decrease
+         in speedtest1).
+      */
+      defaultUnlockAsap: false
+    });
 
     /**
        Runs the given operation (by name) in the async worker
@@ -845,9 +864,15 @@ const installOpfsVfs = function callee(options){
       //xSleep is optionally defined below
       xOpen: function f(pVfs, zName, pFile, flags, pOutFlags){
         mTimeStart('xOpen');
+        let opfsFlags = 0;
         if(0===zName){
           zName = randomFilename();
         }else if('number'===typeof zName){
+          if(capi.sqlite3_uri_boolean(zName, "opfs-unlock-asap", 0)){
+            /* -----------------------^^^^^ MUST pass the untranslated
+               C-string here. */
+            opfsFlags |= state.opfsFlags.OPFS_UNLOCK_ASAP;
+          }
           zName = wasm.cstringToJs(zName);
         }
         const fh = Object.create(null);
@@ -855,7 +880,7 @@ const installOpfsVfs = function callee(options){
         fh.filename = zName;
         fh.sab = new SharedArrayBuffer(state.fileBufferSize);
         fh.flags = flags;
-        const rc = opRun('xOpen', pFile, zName, flags);
+        const rc = opRun('xOpen', pFile, zName, flags, opfsFlags);
         if(!rc){
           /* Recall that sqlite3_vfs::xClose() will be called, even on
              error, unless pFile->pMethods is NULL. */