Improve performance of wal-mode locking on unix in cases where there are hundreds...

FossilOrigin-Name: 30214727f7af9b5471654b0dd2cd234f0e284b24661104e55a9be771baf9577a

diff --git a/manifest b/manifest
index 7aed114cc77114d9c51eb8e471d34e0c7e1cefbf..dc68a9971148210beb61862f1b72520e0436cd67 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Update\sthis\sbranch\swith\slatest\sfrom\sbegin-concurrent-pnu.
-D 2020-08-11T14:06:38.086
+C Improve\sperformance\sof\swal-mode\slocking\son\sunix\sin\scases\swhere\sthere\sare\shundreds\sof\sconnections\sto\sa\ssingle\sdatabase\swithin\sthe\ssame\sprocess.
+D 2020-08-29T15:36:34.942
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -525,7 +525,7 @@ F src/os.c 80e4cf3e5da06be03ca641661e331ce60eeeeabf0d7354dbb1c0e166d0eedbbe
 F src/os.h 48388821692e87da174ea198bf96b1b2d9d83be5dfc908f673ee21fafbe0d432
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
-F src/os_unix.c c79bf7138f5c760bcf167065f08ca1c23f27fe06d8a4ad57432099e966823fe9
+F src/os_unix.c 6315625481f2f2e65a33324730ad94357818c84a00c4459728e00d9cc82c81b9
 F src/os_win.c a2149ff0a85c1c3f9cc102a46c673ce87e992396ba3411bfb53db66813b32f1d
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c 6da497a9d6071d09c5b7d4ae8c5c022a89a625e286d03cc2e1589025cb9a3c07
@@ -1896,7 +1896,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e39e7a6fc793912ab26e5ffc746b38941ec69a7edc100a6034d3ffb1edb606a7 2ae78c993e6a4ffd9ac1c8aaadf4976eacb5486e23c228988e9d3f379ed801c3
-R 791a5872c711641c9ab31256451cd74d
+P 3ee73880ed280f33d554269d4e964cce0c44b5c6c43937da4e547c39f16e860b
+Q +a1c19eea8f141b89a0921da0724096feb21a772ef6654f164e2c36ebf9f7871e
+R 0749a7fd76499ea288e0497f2ffe422d
+T *branch * begin-concurrent-unixshmlock-opt
+T *sym-begin-concurrent-unixshmlock-opt *
+T -sym-begin-concurrent-report *
 U dan
-Z 8cc894655403c6a78b14825962271a49
+Z b30e9f5758699ae064eede4bc7397127

diff --git a/manifest.uuid b/manifest.uuid
index f0fcd4695f9e03e7a8095191c47be5ede4587367..47010edd40df9a242b97638a03eb0f1a6824d9b5 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-3ee73880ed280f33d554269d4e964cce0c44b5c6c43937da4e547c39f16e860b
\ No newline at end of file
+30214727f7af9b5471654b0dd2cd234f0e284b24661104e55a9be771baf9577a
\ No newline at end of file

diff --git a/src/os_unix.c b/src/os_unix.c
index 808d7fc7a7a74b29d47561c1eb60ab44268e23ed..c1195db9d3b9b338d7c4cfb26bf9267521459948 100644 (file)
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -4276,6 +4276,7 @@ struct unixShmNode {
   char **apRegion;           /* Array of mapped shared-memory regions */
   int nRef;                  /* Number of unixShm objects pointing to this */
   unixShm *pFirst;           /* All unixShm objects pointing to this */
+  int aLock[SQLITE_SHM_NLOCK];  /* # shared locks on slot, -1==excl lock */
 #ifdef SQLITE_DEBUG
   u8 exclMask;               /* Mask of exclusive locks held */
   u8 sharedMask;             /* Mask of shared locks held */
@@ -4816,6 +4817,38 @@ shmpage_out:
   return rc;
 }
 
+/*
+** Check that the pShmNode->aLock[] array comports with the locking bitmasks
+** held by each client. Return true if it does, or false otherwise. This
+** is to be used in an assert(). e.g.
+**
+**     assert( assertLockingArrayOk(pShmNode) );
+*/
+#ifdef SQLITE_DEBUG
+static int assertLockingArrayOk(unixShmNode *pShmNode){
+  unixShm *pX;
+  int aLock[SQLITE_SHM_NLOCK];
+  assert( sqlite3_mutex_held(pShmNode->pShmMutex) );
+
+  memset(aLock, 0, sizeof(aLock));
+  for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
+    int i;
+    for(i=0; i<SQLITE_SHM_NLOCK; i++){
+      if( pX->exclMask & (1<<i) ){
+        assert( aLock[i]==0 );
+        aLock[i] = -1;
+      }else if( pX->sharedMask & (1<<i) ){
+        assert( aLock[i]>=0 );
+        aLock[i]++;
+      }
+    }
+  }
+
+  assert( 0==memcmp(pShmNode->aLock, aLock, sizeof(aLock)) );
+  return (memcmp(pShmNode->aLock, aLock, sizeof(aLock))==0);
+}
+#endif
+
 /*
 ** Change the lock state for a shared-memory segment.
 **
@@ -4832,10 +4865,10 @@ static int unixShmLock(
 ){
   unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
   unixShm *p = pDbFd->pShm;             /* The shared memory being locked */
-  unixShm *pX;                          /* For looping over all siblings */
   unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
   int rc = SQLITE_OK;                   /* Result code */
   u16 mask;                             /* Mask of locks to take or release */
+  int *aLock = pShmNode->aLock;
 
   assert( pShmNode==pDbFd->pInode->pShmNode );
   assert( pShmNode->pInode==pDbFd->pInode );
@@ -4874,78 +4907,76 @@ static int unixShmLock(
   mask = (1<<(ofst+n)) - (1<<ofst);
   assert( n>1 || mask==(1<<ofst) );
   sqlite3_mutex_enter(pShmNode->pShmMutex);
+  assert( assertLockingArrayOk(pShmNode) );
   if( flags & SQLITE_SHM_UNLOCK ){
-    u16 allMask = 0; /* Mask of locks held by siblings */
+    if( (p->exclMask|p->sharedMask) & mask ){
+      int ii;
+      int bUnlock = 1;
 
-    /* See if any siblings hold this same lock */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( pX==p ) continue;
-      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
-      allMask |= pX->sharedMask;
-    }
+      for(ii=ofst; ii<ofst+n; ii++){
+        if( aLock[ii]>((p->sharedMask & (1<<ii)) ? 1 : 0) ){
+          bUnlock = 0;
+        }
+      }
 
-    /* Unlock the system-level locks */
-    if( (mask & allMask)==0 ){
-      rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
-    }else{
-      rc = SQLITE_OK;
-    }
+      if( bUnlock ){
+        rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
+        if( rc==SQLITE_OK ){
+          memset(&aLock[ofst], 0, sizeof(int)*n);
+        }
+      }else if( p->sharedMask & (1<<ofst) ){
+        assert( n==1 && aLock[ofst]>1 );
+        aLock[ofst]--;
+      }
 
-    /* Undo the local locks */
-    if( rc==SQLITE_OK ){
-      p->exclMask &= ~mask;
-      p->sharedMask &= ~mask;
-    } 
+      /* Undo the local locks */
+      if( rc==SQLITE_OK ){
+        p->exclMask &= ~mask;
+        p->sharedMask &= ~mask;
+      } 
+    }
   }else if( flags & SQLITE_SHM_SHARED ){
-    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
-
-    /* Find out which shared locks are already held by sibling connections.
-    ** If any sibling already holds an exclusive lock, go ahead and return
-    ** SQLITE_BUSY.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 ){
+    assert( n==1 );
+    assert( (p->exclMask & (1<<ofst))==0 );
+    if( (p->sharedMask & mask)==0 ){
+      if( aLock[ofst]<0 ){
         rc = SQLITE_BUSY;
-        break;
-      }
-      allShared |= pX->sharedMask;
-    }
-
-    /* Get shared locks at the system level, if necessary */
-    if( rc==SQLITE_OK ){
-      if( (allShared & mask)==0 ){
+      }else if( aLock[ofst]==0 ){
         rc = unixShmSystemLock(pDbFd, F_RDLCK, ofst+UNIX_SHM_BASE, n);
-      }else{
-        rc = SQLITE_OK;
       }
-    }
 
-    /* Get the local shared locks */
-    if( rc==SQLITE_OK ){
-      p->sharedMask |= mask;
+      /* Get the local shared locks */
+      if( rc==SQLITE_OK ){
+        p->sharedMask |= mask;
+        aLock[ofst]++;
+      }
     }
   }else{
     /* Make sure no sibling connections hold locks that will block this
-    ** lock.  If any do, return SQLITE_BUSY right away.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
+    ** lock.  If any do, return SQLITE_BUSY right away.  */
+    int ii;
+    for(ii=ofst; ii<ofst+n; ii++){
+      assert( (p->sharedMask & mask)==0 );
+      if( (p->exclMask & (1<<ii))==0 && aLock[ii] ){
         rc = SQLITE_BUSY;
         break;
       }
     }
-  
-    /* Get the exclusive locks at the system level.  Then if successful
-    ** also mark the local connection as being locked.
-    */
+
+    /* Get the exclusive locks at the system level. Then if successful
+    ** also update the in-memory values. */
     if( rc==SQLITE_OK ){
       rc = unixShmSystemLock(pDbFd, F_WRLCK, ofst+UNIX_SHM_BASE, n);
       if( rc==SQLITE_OK ){
         assert( (p->sharedMask & mask)==0 );
         p->exclMask |= mask;
+        for(ii=ofst; ii<ofst+n; ii++){
+          aLock[ii] = -1;
+        }
       }
     }
   }
+  assert( assertLockingArrayOk(pShmNode) );
   sqlite3_mutex_leave(pShmNode->pShmMutex);
   OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
            p->id, osGetpid(0), p->sharedMask, p->exclMask));