private void Hit(WindowCache.Ref r) { // We don't need to be 100% accurate here. Its sufficient that at least // one thread performs the increment. Any other concurrent access at // exactly the same time can simply use the same clock value. // // Consequently we attempt the set, but we don't try to recover should // it fail. This is why we don't use getAndIncrement() here. // long c = clock.Get(); clock.CompareAndSet(c, c + 1); r.lastAccess = c; }
/// <summary>Lookup a cached object, creating and loading it if it doesn't exist.</summary> /// <remarks>Lookup a cached object, creating and loading it if it doesn't exist.</remarks> /// <param name="pack">the pack that "contains" the cached object.</param> /// <param name="position">offset within <code>pack</code> of the object.</param> /// <returns>the object reference.</returns> /// <exception cref="System.IO.IOException"> /// the object reference was not in the cache and could not be /// obtained by /// <see cref="Load(PackFile, long)">Load(PackFile, long)</see> /// . /// </exception> private ByteWindow GetOrLoad(PackFile pack, long position) { int slot = Slot(pack, position); WindowCache.Entry e1 = table.Get(slot); ByteWindow v = Scan(e1, pack, position); if (v != null) { return(v); } lock (LockCache(pack, position)) { WindowCache.Entry e2 = table.Get(slot); if (e2 != e1) { v = Scan(e2, pack, position); if (v != null) { return(v); } } v = Load(pack, position); WindowCache.Ref @ref = CreateRef(pack, position, v); Hit(@ref); for (; ;) { WindowCache.Entry n = new WindowCache.Entry(Clean(e2), @ref); if (table.CompareAndSet(slot, e2, n)) { break; } e2 = table.Get(slot); } } if (evictLock.TryLock()) { try { Gc(); Evict(); } finally { evictLock.Unlock(); } } return(v); }
private ByteWindow Scan(WindowCache.Entry n, PackFile pack, long position) { for (; n != null; n = n.next) { WindowCache.Ref r = n.@ref; if (r.pack == pack && r.position == position) { ByteWindow v = r.Get(); if (v != null) { Hit(r); return(v); } n.Kill(); break; } } return(null); }
internal Entry(WindowCache.Entry n, WindowCache.Ref r) { next = n; @ref = r; }
private void Clear(WindowCache.Ref @ref) { openBytes.AddAndGet([email protected]); Close(@ref.pack); }
private WindowCache.Ref CreateRef(PackFile p, long o, ByteWindow v) { WindowCache.Ref @ref = new WindowCache.Ref(p, o, v, queue); openBytes.AddAndGet(@ref.size); return(@ref); }