new linux futex calls to manage contention

[btree] / fosterbtreeg.c

diff --git a/fosterbtreeg.c b/fosterbtreeg.c
index 1652450d7765d4dc1eec64bd16929cbebdc8af55..fdd42be4f507186b1c078104ce34a2b3525d9f18 100644 (file)
--- a/fosterbtreeg.c
+++ b/fosterbtreeg.c
@@ -142,10 +142,10 @@ typedef struct Page {
        BtSpinLatch readwr[1];          // read/write lock
        BtSpinLatch access[1];          // access intent lock
        BtSpinLatch parent[1];          // parent SMO lock
+       ushort foster;                          // count of foster children
        uint cnt;                                       // count of keys in page
        uint act;                                       // count of active keys
        uint min;                                       // next key offset
-       uint foster;                            // count of foster children
        unsigned char bits;                     // page size in bits
        unsigned char lvl:6;            // level of page
        unsigned char kill:1;           // page is being deleted
@@ -159,7 +159,7 @@ typedef struct {
        unsigned long long int lru;     // number of times accessed
        uid  basepage;                          // mapped base page number
        char *map;                                      // mapped memory pointer
-       ushort pin;                                     // mapped page pin counter
+       volatile ushort pin;            // mapped page pin counter
        ushort slot;                            // slot index in this array
        void *hashprev;                         // previous pool entry for the same hash idx
        void *hashnext;                         // next pool entry for the same hash idx
@@ -181,11 +181,11 @@ typedef struct {
 #else
        HANDLE idx;
 #endif
-       ushort poolcnt;                         // highest page pool node in use
+       volatile ushort poolcnt;        // highest page pool node in use
+       volatile ushort evicted;        // last evicted hash table slot
        ushort poolmax;                         // highest page pool node allocated
        ushort poolmask;                        // total size of pages in mmap segment - 1
        ushort hashsize;                        // size of Hash Table for pool entries
-       ushort evicted;                         // last evicted hash table slot
        ushort *hash;                           // hash table of pool entries
        BtPool *pool;                           // memory pool page segments
        BtSpinLatch *latch;                     // latches for pool hash slots
@@ -319,19 +319,26 @@ ushort prev;
 
   do {
 #ifdef unix
-       do prev = __sync_fetch_and_or((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       while( __sync_fetch_and_or((ushort *)latch, Mutex) & Mutex )
+               sched_yield();
 #else
-       do prev = _InterlockedOr16((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       while( _InterlockedOr16((ushort *)latch, Mutex) & Mutex )
+               SwitchToThread();
 #endif
-
-       //  see if exclusive request is pending, or granted
+       //  see if exclusive request is granted or pending
 
        if( prev = !(latch->exclusive | latch->pending) )
-               latch->share++;
+#ifdef unix
+               __sync_fetch_and_add((ushort *)latch, Share);
+#else
+               _InterlockedExchangeAdd16 ((ushort *)latch, Share);
+#endif
 
-       latch->mutex = 0;
+#ifdef unix
+       __sync_fetch_and_and ((ushort *)latch, ~Mutex);
+#else
+       _InterlockedAnd16((ushort *)latch, ~Mutex);
+#endif
 
        if( prev )
                return;
@@ -350,16 +357,24 @@ ushort prev;
 
   do {
 #ifdef  unix
-       do prev = __sync_fetch_and_or((ushort *)latch, (Pending | Mutex));
-       while( prev & Mutex );
+       while( __sync_fetch_and_or((ushort *)latch, Mutex | Pending) & Mutex )
+               sched_yield();
 #else
-       do prev = _InterlockedOr16((ushort *)latch, (Pending | Mutex));
-       while( prev & Mutex );
+       while( _InterlockedOr16((ushort *)latch, Mutex | Pending) & Mutex )
+               SwitchToThread();
 #endif
        if( prev = !(latch->share | latch->exclusive) )
-               latch->exclusive = 1, latch->pending = 0;
+#ifdef unix
+               __sync_fetch_and_or((ushort *)latch, Write);
+#else
+               _InterlockedOr16((ushort *)latch, Write);
+#endif
 
-       latch->mutex = 0;
+#ifdef unix
+       __sync_fetch_and_and ((ushort *)latch, ~(Mutex | Pending));
+#else
+       _InterlockedAnd16((ushort *)latch, ~(Mutex | Pending));
+#endif
 
        if( prev )
                return;
@@ -381,18 +396,20 @@ int bt_spinwritetry(BtSpinLatch *latch)
 ushort prev;
 
 #ifdef unix
-       do prev = __sync_fetch_and_or((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       if( prev = __sync_fetch_and_or((ushort *)latch, Mutex), prev & Mutex )
+               return 0;
 #else
-       do prev = _InterlockedOr16((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       if( prev = _InterlockedOr16((ushort *)latch, Mutex), prev & Mutex )
+               return 0;
 #endif
        //      take write access if all bits are clear
 
        if( !prev )
-               latch->exclusive = 1;
-
-       latch->mutex = 0;
+#ifdef unix
+               __sync_fetch_and_or ((ushort *)latch, Write);
+#else
+               _InterlockedOr16((ushort *)latch, Write);
+#endif
        return !prev;
 }
 
@@ -400,36 +417,22 @@ ushort prev;
 
 void bt_spinreleasewrite(BtSpinLatch *latch)
 {
-ushort prev;
-
 #ifdef unix
-       do prev = __sync_fetch_and_or((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       __sync_fetch_and_and ((ushort *)latch, ~Write);
 #else
-       do prev = _InterlockedOr16((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       _InterlockedAnd16((ushort *)latch, ~Write);
 #endif
-
-       latch->exclusive = 0;
-       latch->mutex = 0;
 }
 
 //     decrement reader count
 
 void bt_spinreleaseread(BtSpinLatch *latch)
 {
-ushort prev;
-
 #ifdef unix
-       do prev = __sync_fetch_and_or((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       __sync_fetch_and_add((ushort *)latch, -Share);
 #else
-       do prev = _InterlockedOr16((ushort *)latch, Mutex);
-       while( prev & Mutex );
+       _InterlockedExchangeAdd16 ((ushort *)latch, -Share);
 #endif
-
-       latch->share--;
-       latch->mutex = 0;
 }
 
 void bt_mgrclose (BtMgr *mgr)
@@ -1138,11 +1141,12 @@ uid bt_newpage(BtDb *bt, BtPage page)
 {
 uid new_page;
 BtPage pmap;
+int subpage;
 int reuse;
 
-       //      lock allocation page
+       // lock page zero
 
-       if ( bt_lockpage(bt, ALLOC_page, BtLockWrite, &bt->alloc) )
+       if( bt_lockpage(bt, ALLOC_page, BtLockWrite, &bt->alloc) )
                return 0;
 
        // use empty chain first
@@ -1160,6 +1164,7 @@ int reuse;
                bt_putid(bt->alloc->right, new_page+1);
                reuse = 0;
        }
+
 #ifdef unix
        memset(bt->zero, 0, 3 * sizeof(BtSpinLatch)); // clear locks
        memcpy((char *)bt->zero + 3 * sizeof(BtSpinLatch), (char *)page + 3 * sizeof(BtSpinLatch), bt->mgr->page_size - 3 * sizeof(BtSpinLatch));
@@ -1182,7 +1187,9 @@ int reuse;
        if( bt_lockpage(bt, new_page, BtLockWrite, &pmap) )
                return 0;
 
-       memcpy(pmap, page, bt->mgr->page_size);
+       //  copy source page, but leave latch area intact
+
+       memcpy((char *)pmap + 3 * sizeof(BtSpinLatch), (char *)page + 3 * sizeof(BtSpinLatch), bt->mgr->page_size - 3 * sizeof(BtSpinLatch));
 
        if( bt_unlockpage (bt, new_page, BtLockWrite) )
                return 0;