From 44d65ea1615099ae252407f2554338d450cfdb1c Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 6 Oct 2016 11:39:10 +0200
Subject: ringtest: use link-time optimization
By using -flto and -fwhole-program, all functions from the ring implementation
can be treated as static and possibly inlined. Force this to happen through
the GCC flatten attribute.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
tools/virtio/ringtest/main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
(limited to 'tools/virtio/ringtest/main.c')
diff --git a/tools/virtio/ringtest/main.c b/tools/virtio/ringtest/main.c
index 147abb452a6c..bda7f0dad981 100644
--- a/tools/virtio/ringtest/main.c
+++ b/tools/virtio/ringtest/main.c
@@ -96,7 +96,7 @@ void set_affinity(const char *arg)
assert(!ret);
}
-static void run_guest(void)
+static void __attribute__((__flatten__)) run_guest(void)
{
int completed_before;
int completed = 0;
@@ -149,7 +149,7 @@ static void run_guest(void)
}
}
-static void run_host(void)
+static void __attribute__((__flatten__)) run_host(void)
{
int completed_before;
int completed = 0;
--
cgit v1.2.3
From d3c3589b8b3cd4fabf4cd137facb42a7fb36bd7f Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 6 Oct 2016 11:39:11 +0200
Subject: ringtest: commonize implementation of poll_avail/poll_used
Provide new primitives used_empty/avail_empty and
build poll_avail/poll_used on top of it.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
tools/virtio/ringtest/main.c | 12 +++++++
tools/virtio/ringtest/main.h | 4 +--
tools/virtio/ringtest/noring.c | 6 ++--
tools/virtio/ringtest/ptr_ring.c | 22 +++---------
tools/virtio/ringtest/ring.c | 18 ++++------
tools/virtio/ringtest/virtio_ring_0_9.c | 64 ++++++++-------------------------
6 files changed, 43 insertions(+), 83 deletions(-)
(limited to 'tools/virtio/ringtest/main.c')
diff --git a/tools/virtio/ringtest/main.c b/tools/virtio/ringtest/main.c
index bda7f0dad981..b00ecd619969 100644
--- a/tools/virtio/ringtest/main.c
+++ b/tools/virtio/ringtest/main.c
@@ -96,6 +96,12 @@ void set_affinity(const char *arg)
assert(!ret);
}
+void poll_used(void)
+{
+ while (used_empty())
+ busy_wait();
+}
+
static void __attribute__((__flatten__)) run_guest(void)
{
int completed_before;
@@ -149,6 +155,12 @@ static void __attribute__((__flatten__)) run_guest(void)
}
}
+void poll_avail(void)
+{
+ while (avail_empty())
+ busy_wait();
+}
+
static void __attribute__((__flatten__)) run_host(void)
{
int completed_before;
diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h
index 16917acb0ade..34e63cc4c572 100644
--- a/tools/virtio/ringtest/main.h
+++ b/tools/virtio/ringtest/main.h
@@ -56,15 +56,15 @@ void alloc_ring(void);
int add_inbuf(unsigned, void *, void *);
void *get_buf(unsigned *, void **);
void disable_call();
+bool used_empty();
bool enable_call();
void kick_available();
-void poll_used();
/* host side */
void disable_kick();
+bool avail_empty();
bool enable_kick();
bool use_buf(unsigned *, void **);
void call_used();
-void poll_avail();
/* implemented by main */
extern bool do_sleep;
diff --git a/tools/virtio/ringtest/noring.c b/tools/virtio/ringtest/noring.c
index eda2f4824130..b8d1c1daac7c 100644
--- a/tools/virtio/ringtest/noring.c
+++ b/tools/virtio/ringtest/noring.c
@@ -24,8 +24,9 @@ void *get_buf(unsigned *lenp, void **bufp)
return "Buffer";
}
-void poll_used(void)
+bool used_empty()
{
+ return false;
}
void disable_call()
@@ -54,8 +55,9 @@ bool enable_kick()
assert(0);
}
-void poll_avail(void)
+bool avail_empty()
{
+ return false;
}
bool use_buf(unsigned *lenp, void **bufp)
diff --git a/tools/virtio/ringtest/ptr_ring.c b/tools/virtio/ringtest/ptr_ring.c
index bd2ad1d3b7a9..635b07b4fdd3 100644
--- a/tools/virtio/ringtest/ptr_ring.c
+++ b/tools/virtio/ringtest/ptr_ring.c
@@ -133,18 +133,9 @@ void *get_buf(unsigned *lenp, void **bufp)
return datap;
}
-void poll_used(void)
+bool used_empty()
{
- void *b;
-
- do {
- if (tailcnt == headcnt || __ptr_ring_full(&array)) {
- b = NULL;
- barrier();
- } else {
- b = "Buffer\n";
- }
- } while (!b);
+ return (tailcnt == headcnt || __ptr_ring_full(&array));
}
void disable_call()
@@ -173,14 +164,9 @@ bool enable_kick()
assert(0);
}
-void poll_avail(void)
+bool avail_empty()
{
- void *b;
-
- do {
- barrier();
- b = __ptr_ring_peek(&array);
- } while (!b);
+ return !__ptr_ring_peek(&array);
}
bool use_buf(unsigned *lenp, void **bufp)
diff --git a/tools/virtio/ringtest/ring.c b/tools/virtio/ringtest/ring.c
index c25c8d248b6b..747c5dd47be8 100644
--- a/tools/virtio/ringtest/ring.c
+++ b/tools/virtio/ringtest/ring.c
@@ -163,12 +163,11 @@ void *get_buf(unsigned *lenp, void **bufp)
return datap;
}
-void poll_used(void)
+bool used_empty()
{
unsigned head = (ring_size - 1) & guest.last_used_idx;
- while (ring[head].flags & DESC_HW)
- busy_wait();
+ return (ring[head].flags & DESC_HW);
}
void disable_call()
@@ -180,13 +179,11 @@ void disable_call()
bool enable_call()
{
- unsigned head = (ring_size - 1) & guest.last_used_idx;
-
event->call_index = guest.last_used_idx;
/* Flush call index write */
/* Barrier D (for pairing) */
smp_mb();
- return ring[head].flags & DESC_HW;
+ return used_empty();
}
void kick_available(void)
@@ -213,20 +210,17 @@ void disable_kick()
bool enable_kick()
{
- unsigned head = (ring_size - 1) & host.used_idx;
-
event->kick_index = host.used_idx;
/* Barrier C (for pairing) */
smp_mb();
- return !(ring[head].flags & DESC_HW);
+ return avail_empty();
}
-void poll_avail(void)
+bool avail_empty()
{
unsigned head = (ring_size - 1) & host.used_idx;
- while (!(ring[head].flags & DESC_HW))
- busy_wait();
+ return !(ring[head].flags & DESC_HW);
}
bool use_buf(unsigned *lenp, void **bufp)
diff --git a/tools/virtio/ringtest/virtio_ring_0_9.c b/tools/virtio/ringtest/virtio_ring_0_9.c
index 761866212aac..bbc3043b2fb1 100644
--- a/tools/virtio/ringtest/virtio_ring_0_9.c
+++ b/tools/virtio/ringtest/virtio_ring_0_9.c
@@ -194,24 +194,16 @@ void *get_buf(unsigned *lenp, void **bufp)
return datap;
}
-void poll_used(void)
+bool used_empty()
{
+ unsigned short last_used_idx = guest.last_used_idx;
#ifdef RING_POLL
- unsigned head = (ring_size - 1) & guest.last_used_idx;
+ unsigned short head = last_used_idx & (ring_size - 1);
+ unsigned index = ring.used->ring[head].id;
- for (;;) {
- unsigned index = ring.used->ring[head].id;
-
- if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1))
- busy_wait();
- else
- break;
- }
+ return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1);
#else
- unsigned head = guest.last_used_idx;
-
- while (ring.used->idx == head)
- busy_wait();
+ return ring.used->idx == last_used_idx;
#endif
}
@@ -224,22 +216,11 @@ void disable_call()
bool enable_call()
{
- unsigned short last_used_idx;
-
- vring_used_event(&ring) = (last_used_idx = guest.last_used_idx);
+ vring_used_event(&ring) = guest.last_used_idx;
/* Flush call index write */
/* Barrier D (for pairing) */
smp_mb();
-#ifdef RING_POLL
- {
- unsigned short head = last_used_idx & (ring_size - 1);
- unsigned index = ring.used->ring[head].id;
-
- return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1);
- }
-#else
- return ring.used->idx == last_used_idx;
-#endif
+ return used_empty();
}
void kick_available(void)
@@ -266,36 +247,21 @@ void disable_kick()
bool enable_kick()
{
- unsigned head = host.used_idx;
-
- vring_avail_event(&ring) = head;
+ vring_avail_event(&ring) = host.used_idx;
/* Barrier C (for pairing) */
smp_mb();
-#ifdef RING_POLL
- {
- unsigned index = ring.avail->ring[head & (ring_size - 1)];
-
- return (index ^ head ^ 0x8000) & ~(ring_size - 1);
- }
-#else
- return head == ring.avail->idx;
-#endif
+ return avail_empty();
}
-void poll_avail(void)
+bool avail_empty()
{
unsigned head = host.used_idx;
#ifdef RING_POLL
- for (;;) {
- unsigned index = ring.avail->ring[head & (ring_size - 1)];
- if ((index ^ head ^ 0x8000) & ~(ring_size - 1))
- busy_wait();
- else
- break;
- }
+ unsigned index = ring.avail->ring[head & (ring_size - 1)];
+
+ return ((index ^ head ^ 0x8000) & ~(ring_size - 1));
#else
- while (ring.avail->idx == head)
- busy_wait();
+ return head == ring.avail->idx;
#endif
}
--
cgit v1.2.3
From 948a8ac2964f39161ebf832dea0aa1ced90101bb Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 6 Oct 2016 11:39:12 +0200
Subject: ringtest: poll for new buffers once before updating event index
Updating the event index has a memory barrier and causes more work
on the other side to actually signal the event. It is unnecessary
if a new buffer has already appeared on the ring, so poll once before
doing the update.
The effect of this on the 0.9 ring implementation is pretty much
invisible, but on the new-style ring it provides a consistent 3%
performance improvement.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
tools/virtio/ringtest/main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
(limited to 'tools/virtio/ringtest/main.c')
diff --git a/tools/virtio/ringtest/main.c b/tools/virtio/ringtest/main.c
index b00ecd619969..f31353fac541 100644
--- a/tools/virtio/ringtest/main.c
+++ b/tools/virtio/ringtest/main.c
@@ -147,7 +147,7 @@ static void __attribute__((__flatten__)) run_guest(void)
assert(completed <= bufs);
assert(started <= bufs);
if (do_sleep) {
- if (enable_call())
+ if (used_empty() && enable_call())
wait_for_call();
} else {
poll_used();
@@ -172,7 +172,7 @@ static void __attribute__((__flatten__)) run_host(void)
for (;;) {
if (do_sleep) {
- if (enable_kick())
+ if (avail_empty() && enable_kick())
wait_for_kick();
} else {
poll_avail();
--
cgit v1.2.3