diff --git a/source/lib/bits.h b/source/lib/bits.h
index be203cc8d9..094fa34496 100644
--- a/source/lib/bits.h
+++ b/source/lib/bits.h
@@ -152,6 +152,9 @@ inline bool is_pow2(T n)
 	return (n & (n-1)) == 0;
 }
 
+// as above; intended for use in static_assert
+#define IS_POW2(n) (((n) != 0) && ((n) & ((n)-1)) == 0)
+
 template<typename T>
 inline T LeastSignificantBit(T x)
 {
@@ -165,6 +168,7 @@ inline T ClearLeastSignificantBit(T x)
 	return x & (x-1);
 }
 
+
 /**
  * ceil(log2(x))
  *
@@ -186,6 +190,26 @@ inline size_t ceil_log2(T x)
 	return log;
 }
 
+// compile-time variant of the above
+template<size_t N>
+struct CeilLog2
+{
+	enum { value = 1 + CeilLog2<(N+1)/2>::value };
+};
+
+template<>
+struct CeilLog2<1>
+{
+	enum { value = 0 };
+};
+
+template<>
+struct CeilLog2<0>
+{
+	enum { value = 0 };
+};
+
+
 
 /**
  * floor(log2(f))
diff --git a/source/lib/file/io/io.h b/source/lib/file/io/io.h
index 4510ca0a86..e0f68a9423 100644
--- a/source/lib/file/io/io.h
+++ b/source/lib/file/io/io.h
@@ -223,6 +223,10 @@ LIB_API Status WaitUntilComplete(aiocb& cb, size_t queueDepth);
 //-----------------------------------------------------------------------------
 // Run
 
+#ifndef ENABLE_IO_STATS
+#define ENABLE_IO_STATS 0
+#endif
+
 // (hooks must be passed by const reference to allow passing rvalues.
 // functors with non-const member data can mark them as mutable.)
 template<class CompletedHook, class IssueHook>
@@ -233,6 +237,11 @@ static inline Status Run(const Operation& op, const Parameters& p = Parameters()
 
 	ControlBlockRingBuffer controlBlockRingBuffer(op, p);
 
+#if ENABLE_IO_STATS
+	const double t0 = timer_Time();
+	COMPILER_FENCE;
+#endif
+
 	const off_t numBlocks = p.blockSize? (off_t)DivideRoundUp((u64)op.size, (u64)p.blockSize) : 1;
 	for(off_t blocksIssued = 0, blocksCompleted = 0; blocksCompleted < numBlocks; blocksCompleted++)
 	{
@@ -256,6 +265,13 @@ static inline Status Run(const Operation& op, const Parameters& p = Parameters()
 		RETURN_STATUS_FROM_CALLBACK(completedHook((u8*)cb.aio_buf, cb.aio_nbytes));
 	}
 
+#if ENABLE_IO_STATS
+	COMPILER_FENCE;
+	const double t1 = timer_Time();
+	const off_t totalSize = p.blockSize? numBlocks*p.blockSize : op.size;
+	debug_printf(L"IO: %.2f MB/s (%.2f)\n", totalSize/(t1-t0)/1e6, (t1-t0)*1e3);
+#endif
+
 	return INFO::OK;
 }