stream: move rate limiting to a separate header file

Make the code reusable.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/include/qemu/ratelimit.h b/include/qemu/ratelimit.h
new file mode 100644
index 0000000000..c6ac281141
--- /dev/null
+++ b/include/qemu/ratelimit.h
@@ -0,0 +1,48 @@
+/*
+ * Ratelimiting calculations
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_RATELIMIT_H
+#define QEMU_RATELIMIT_H 1
+
+typedef struct {
+    int64_t next_slice_time;
+    uint64_t slice_quota;
+    uint64_t slice_ns;
+    uint64_t dispatched;
+} RateLimit;
+
+static inline int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
+{
+    int64_t now = qemu_get_clock_ns(rt_clock);
+
+    if (limit->next_slice_time < now) {
+        limit->next_slice_time = now + limit->slice_ns;
+        limit->dispatched = 0;
+    }
+    if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota) {
+        limit->dispatched += n;
+        return 0;
+    } else {
+        limit->dispatched = n;
+        return limit->next_slice_time - now;
+    }
+}
+
+static inline void ratelimit_set_speed(RateLimit *limit, uint64_t speed,
+                                       uint64_t slice_ns)
+{
+    limit->slice_ns = slice_ns;
+    limit->slice_quota = ((double)speed * 1000000000ULL) / slice_ns;
+}
+
+#endif