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authorMichael S. Tsirkin <mst@redhat.com>2016-01-21 15:44:10 +0300
committerMichael S. Tsirkin <mst@redhat.com>2016-01-26 11:18:30 +0300
commit481eaec37e91e2b33f17275901172f50ce2c71e8 (patch)
treecd0df9f9f652f12820d5f615a0016da3f98839d4 /tools/virtio/ringtest/main.h
parentfb9b050ce9695cf2769a850d94aa2ab39c8c3cd5 (diff)
downloadlinux-481eaec37e91e2b33f17275901172f50ce2c71e8.tar.xz
tools/virtio: add ringtest utilities
This adds micro-benchmarks useful for tuning virtio ring layouts. Three layouts are currently implemented: - virtio 0.9 compatible one - an experimental extension bypassing the ring index, polling ring itself instead - an experimental extension bypassing avail and used ring completely Typical use: sh run-on-all.sh perf stat -r 10 --log-fd 1 -- ./ring It doesn't depend on the kernel directly, but it's handy to have as much virtio stuff as possible in one tree. Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'tools/virtio/ringtest/main.h')
-rw-r--r--tools/virtio/ringtest/main.h119
1 files changed, 119 insertions, 0 deletions
diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h
new file mode 100644
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+++ b/tools/virtio/ringtest/main.h
@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Common macros and functions for ring benchmarking.
+ */
+#ifndef MAIN_H
+#define MAIN_H
+
+#include <stdbool.h>
+
+extern bool do_exit;
+
+#if defined(__x86_64__) || defined(__i386__)
+#include "x86intrin.h"
+
+static inline void wait_cycles(unsigned long long cycles)
+{
+ unsigned long long t;
+
+ t = __rdtsc();
+ while (__rdtsc() - t < cycles) {}
+}
+
+#define VMEXIT_CYCLES 500
+#define VMENTRY_CYCLES 500
+
+#else
+static inline void wait_cycles(unsigned long long cycles)
+{
+ _Exit(5);
+}
+#define VMEXIT_CYCLES 0
+#define VMENTRY_CYCLES 0
+#endif
+
+static inline void vmexit(void)
+{
+ if (!do_exit)
+ return;
+
+ wait_cycles(VMEXIT_CYCLES);
+}
+static inline void vmentry(void)
+{
+ if (!do_exit)
+ return;
+
+ wait_cycles(VMENTRY_CYCLES);
+}
+
+/* implemented by ring */
+void alloc_ring(void);
+/* guest side */
+int add_inbuf(unsigned, void *, void *);
+void *get_buf(unsigned *, void **);
+void disable_call();
+bool enable_call();
+void kick_available();
+void poll_used();
+/* host side */
+void disable_kick();
+bool enable_kick();
+bool use_buf(unsigned *, void **);
+void call_used();
+void poll_avail();
+
+/* implemented by main */
+extern bool do_sleep;
+void kick(void);
+void wait_for_kick(void);
+void call(void);
+void wait_for_call(void);
+
+extern unsigned ring_size;
+
+/* Compiler barrier - similar to what Linux uses */
+#define barrier() asm volatile("" ::: "memory")
+
+/* Is there a portable way to do this? */
+#if defined(__x86_64__) || defined(__i386__)
+#define cpu_relax() asm ("rep; nop" ::: "memory")
+#else
+#define cpu_relax() assert(0)
+#endif
+
+extern bool do_relax;
+
+static inline void busy_wait(void)
+{
+ if (do_relax)
+ cpu_relax();
+ else
+ /* prevent compiler from removing busy loops */
+ barrier();
+}
+
+/*
+ * Not using __ATOMIC_SEQ_CST since gcc docs say they are only synchronized
+ * with other __ATOMIC_SEQ_CST calls.
+ */
+#define smp_mb() __sync_synchronize()
+
+/*
+ * This abuses the atomic builtins for thread fences, and
+ * adds a compiler barrier.
+ */
+#define smp_release() do { \
+ barrier(); \
+ __atomic_thread_fence(__ATOMIC_RELEASE); \
+} while (0)
+
+#define smp_acquire() do { \
+ __atomic_thread_fence(__ATOMIC_ACQUIRE); \
+ barrier(); \
+} while (0)
+
+#endif