Stefano Stabellini
2012-Apr-13 18:33 UTC
[PATCH v6 0/5] prevent QEMU from waking up needlessly
Hi all,
this small patch series prevents QEMU from waking up needlessly on Xen
several times a second in order to check some timers.
The first patch stops QEMU from emulating the PIT on Xen, the second
patch disables the rtc_clock entirely.
The third patch fixes win32_rearm_timer and mm_rearm_timer that
risk an overflow if INT64_MAX is passed as delta.
The fourth patch changes qemu_next_alarm_deadline only to check the
expire time of a clock if it is enabled.
Finally the last patch makes main_loop_wait wait indefinitely on select
unless we actually need a timeout.
Changes in v6:
- rebase on 7672725d41d1a04195affc1a7bd5676ba6314b14;
- dropped the buffered IO patch, that has been handled separately from
this series.
Changes in v5:
- remove the last patch to increase the timeout to 1h, replace it with a
patch to wait indefinitely on select unless we need a timeout.
Changes in v4:
- do not initialize pcspk on xen;
- disable rtc_clock only when it points to the host_clock (the default);
- make sure it compiles on older xen versions.
Changes in v3:
- added a new patch to fix win32_rearm_timer and mm_rearm_timer, that
risk an overflow if INT64_MAX is passed as delta.
Shortlog and diffstat follow:
Stefano Stabellini (5):
xen: do not initialize the interval timer and PCSPK emulator
xen: disable rtc_clock
timers: the rearm function should be able to handle delta = INT64_MAX
qemu_next_alarm_deadline: check the expire time of a clock only if it is
enabled
main_loop_wait: block indefinitely
async.c | 2 +-
hw/pc.c | 9 ++++++---
main-loop.c | 23 ++++++++++++++---------
main-loop.h | 2 +-
qemu-timer.c | 33 +++++++++++++++++----------------
qemu-timer.h | 1 -
qemu-tool.c | 4 ++++
slirp/libslirp.h | 1 +
slirp/slirp.c | 7 +++++++
xen-all.c | 4 ++++
10 files changed, 55 insertions(+), 31 deletions(-)
A git tree, based on 7672725d41d1a04195affc1a7bd5676ba6314b14, is available
here:
git://xenbits.xen.org/people/sstabellini/qemu-dm.git timers-6
Cheers,
Stefano
Stefano Stabellini
2012-Apr-13 18:35 UTC
[PATCH v6 1/5] xen: do not initialize the interval timer and PCSPK emulator
PIT and PCSPK are emulated by the hypervisor so we don''t need to
emulate
them in Qemu: this patch prevents Qemu from waking up needlessly at
PIT_FREQ on Xen.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
hw/pc.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/hw/pc.c b/hw/pc.c
index 67f0479..08c69e9 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -46,6 +46,7 @@
#include "ui/qemu-spice.h"
#include "memory.h"
#include "exec-memory.h"
+#include "arch_init.h"
/* output Bochs bios info messages */
//#define DEBUG_BIOS
@@ -1089,7 +1090,7 @@ void pc_basic_device_init(ISABus *isa_bus, qemu_irq *gsi,
qemu_irq pit_alt_irq = NULL;
qemu_irq rtc_irq = NULL;
qemu_irq *a20_line;
- ISADevice *i8042, *port92, *vmmouse, *pit;
+ ISADevice *i8042, *port92, *vmmouse, *pit = NULL;
qemu_irq *cpu_exit_irq;
register_ioport_write(0x80, 1, 1, ioport80_write, NULL);
@@ -1120,14 +1121,16 @@ void pc_basic_device_init(ISABus *isa_bus, qemu_irq
*gsi,
if (kvm_irqchip_in_kernel()) {
pit = kvm_pit_init(isa_bus, 0x40);
- } else {
+ } else if (!xen_available()) {
pit = pit_init(isa_bus, 0x40, pit_isa_irq, pit_alt_irq);
}
if (hpet) {
/* connect PIT to output control line of the HPET */
qdev_connect_gpio_out(hpet, 0, qdev_get_gpio_in(&pit->qdev, 0));
}
- pcspk_init(isa_bus, pit);
+ if (!xen_available()) {
+ pcspk_init(isa_bus, pit);
+ }
for(i = 0; i < MAX_SERIAL_PORTS; i++) {
if (serial_hds[i]) {
--
1.7.2.5
rtc_clock is only used by the RTC emulator (mc146818rtc.c), however Xen
has its own RTC emulator in the hypervisor so we can disable it.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
xen-all.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/xen-all.c b/xen-all.c
index 3e6de41..d1c4e72 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -593,6 +593,10 @@ void xen_vcpu_init(void)
qemu_register_reset(xen_reset_vcpu, first_cpu);
xen_reset_vcpu(first_cpu);
}
+ /* if rtc_clock is left to default (host_clock), disable it */
+ if (rtc_clock == host_clock) {
+ qemu_clock_enable(rtc_clock, false);
+ }
}
/* get the ioreq packets from share mem */
--
1.7.2.5
Stefano Stabellini
2012-Apr-13 18:35 UTC
[PATCH v6 3/5] timers: the rearm function should be able to handle delta = INT64_MAX
Fix win32_rearm_timer and mm_rearm_timer: they should be able to handle
INT64_MAX as a delta parameter without overflowing.
Also, the next deadline in ms should be calculated rounding down rather
than up (see unix_rearm_timer and dynticks_rearm_timer).
Finally ChangeTimerQueueTimer takes an unsigned long and timeSetEvent
takes an unsigned int as delta, so cast the ms delta to the appropriate
unsigned integer.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
qemu-timer.c | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/qemu-timer.c b/qemu-timer.c
index 80bcc56..fe4cd6f 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -696,13 +696,17 @@ static void mm_stop_timer(struct qemu_alarm_timer *t)
static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
{
- int nearest_delta_ms = (delta + 999999) / 1000000;
+ int64_t nearest_delta_ms = delta / 1000000;
if (nearest_delta_ms < 1) {
nearest_delta_ms = 1;
}
+ /* UINT_MAX can be 32 bit */
+ if (nearest_delta_ms > UINT_MAX) {
+ nearest_delta_ms = UINT_MAX;
+ }
timeKillEvent(mm_timer);
- mm_timer = timeSetEvent(nearest_delta_ms,
+ mm_timer = timeSetEvent((unsigned int) nearest_delta_ms,
mm_period,
mm_alarm_handler,
(DWORD_PTR)t,
@@ -757,16 +761,20 @@ static void win32_rearm_timer(struct qemu_alarm_timer *t,
int64_t nearest_delta_ns)
{
HANDLE hTimer = t->timer;
- int nearest_delta_ms;
+ int64_t nearest_delta_ms;
BOOLEAN success;
- nearest_delta_ms = (nearest_delta_ns + 999999) / 1000000;
+ nearest_delta_ms = nearest_delta_ns / 1000000;
if (nearest_delta_ms < 1) {
nearest_delta_ms = 1;
}
+ /* ULONG_MAX can be 32 bit */
+ if (nearest_delta_ms > ULONG_MAX) {
+ nearest_delta_ms = ULONG_MAX;
+ }
success = ChangeTimerQueueTimer(NULL,
hTimer,
- nearest_delta_ms,
+ (unsigned long) nearest_delta_ms,
3600000);
if (!success) {
--
1.7.2.5
Stefano Stabellini
2012-Apr-13 18:35 UTC
[PATCH v6 4/5] qemu_next_alarm_deadline: check the expire time of a clock only if it is enabled
Also delta in qemu_next_alarm_deadline is a 64 bit value so set the
default to INT64_MAX instead of INT32_MAX.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
qemu-timer.c | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)
diff --git a/qemu-timer.c b/qemu-timer.c
index fe4cd6f..1166beb 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -106,23 +106,21 @@ static inline int alarm_has_dynticks(struct
qemu_alarm_timer *t)
static int64_t qemu_next_alarm_deadline(void)
{
- int64_t delta;
+ int64_t delta = INT64_MAX;
int64_t rtdelta;
- if (!use_icount && vm_clock->active_timers) {
+ if (!use_icount && vm_clock->enabled &&
vm_clock->active_timers) {
delta = vm_clock->active_timers->expire_time -
qemu_get_clock_ns(vm_clock);
- } else {
- delta = INT32_MAX;
}
- if (host_clock->active_timers) {
+ if (host_clock->enabled && host_clock->active_timers) {
int64_t hdelta = host_clock->active_timers->expire_time -
qemu_get_clock_ns(host_clock);
if (hdelta < delta) {
delta = hdelta;
}
}
- if (rt_clock->active_timers) {
+ if (rt_clock->enabled && rt_clock->active_timers) {
rtdelta = (rt_clock->active_timers->expire_time -
qemu_get_clock_ns(rt_clock));
if (rtdelta < delta) {
--
1.7.2.5
Stefano Stabellini
2012-Apr-13 18:35 UTC
[PATCH v6 5/5] main_loop_wait: block indefinitely
- remove qemu_calculate_timeout;
- explicitly size timeout to uint32_t;
- introduce slirp_update_timeout;
- pass NULL as timeout argument to select in case timeout is the maximum
value;
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Paul Brook <paul@codesourcery.com>
---
async.c | 2 +-
main-loop.c | 23 ++++++++++++++---------
main-loop.h | 2 +-
qemu-timer.c | 5 -----
qemu-timer.h | 1 -
qemu-tool.c | 4 ++++
slirp/libslirp.h | 1 +
slirp/slirp.c | 7 +++++++
8 files changed, 28 insertions(+), 17 deletions(-)
diff --git a/async.c b/async.c
index 332d511..ecdaf15 100644
--- a/async.c
+++ b/async.c
@@ -120,7 +120,7 @@ void qemu_bh_delete(QEMUBH *bh)
bh->deleted = 1;
}
-void qemu_bh_update_timeout(int *timeout)
+void qemu_bh_update_timeout(uint32_t *timeout)
{
QEMUBH *bh;
diff --git a/main-loop.c b/main-loop.c
index 1ebdc4b..f363748 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -226,7 +226,7 @@ static int max_priority;
#ifndef _WIN32
static void glib_select_fill(int *max_fd, fd_set *rfds, fd_set *wfds,
- fd_set *xfds, int *cur_timeout)
+ fd_set *xfds, uint32_t *cur_timeout)
{
GMainContext *context = g_main_context_default();
int i;
@@ -288,20 +288,24 @@ static void glib_select_poll(fd_set *rfds, fd_set *wfds,
fd_set *xfds,
}
}
-static int os_host_main_loop_wait(int timeout)
+static int os_host_main_loop_wait(uint32_t timeout)
{
- struct timeval tv;
+ struct timeval tv, *tvarg = NULL;
int ret;
glib_select_fill(&nfds, &rfds, &wfds, &xfds, &timeout);
+ if (timeout < UINT32_MAX) {
+ tvarg = &tv;
+ tv.tv_sec = timeout / 1000;
+ tv.tv_usec = (timeout % 1000) * 1000;
+ }
+
if (timeout > 0) {
qemu_mutex_unlock_iothread();
}
- tv.tv_sec = timeout / 1000;
- tv.tv_usec = (timeout % 1000) * 1000;
- ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv);
+ ret = select(nfds + 1, &rfds, &wfds, &xfds, tvarg);
if (timeout > 0) {
qemu_mutex_lock_iothread();
@@ -400,7 +404,7 @@ void qemu_fd_register(int fd)
FD_CONNECT | FD_WRITE | FD_OOB);
}
-static int os_host_main_loop_wait(int timeout)
+static int os_host_main_loop_wait(uint32_t timeout)
{
GMainContext *context = g_main_context_default();
int ret, i;
@@ -463,12 +467,12 @@ static int os_host_main_loop_wait(int timeout)
int main_loop_wait(int nonblocking)
{
- int ret, timeout;
+ int ret;
+ uint32_t timeout = UINT32_MAX;
if (nonblocking) {
timeout = 0;
} else {
- timeout = qemu_calculate_timeout();
qemu_bh_update_timeout(&timeout);
}
@@ -480,6 +484,7 @@ int main_loop_wait(int nonblocking)
FD_ZERO(&xfds);
#ifdef CONFIG_SLIRP
+ slirp_update_timeout(&timeout);
slirp_select_fill(&nfds, &rfds, &wfds, &xfds);
#endif
qemu_iohandler_fill(&nfds, &rfds, &wfds, &xfds);
diff --git a/main-loop.h b/main-loop.h
index e743aa0..c06b8bc 100644
--- a/main-loop.h
+++ b/main-loop.h
@@ -365,6 +365,6 @@ void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds,
fd_set *xfds, int rc
void qemu_bh_schedule_idle(QEMUBH *bh);
int qemu_bh_poll(void);
-void qemu_bh_update_timeout(int *timeout);
+void qemu_bh_update_timeout(uint32_t *timeout);
#endif
diff --git a/qemu-timer.c b/qemu-timer.c
index 1166beb..887babf 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -821,8 +821,3 @@ fail:
return err;
}
-int qemu_calculate_timeout(void)
-{
- return 1000;
-}
-
diff --git a/qemu-timer.h b/qemu-timer.h
index 661bbe7..094e730 100644
--- a/qemu-timer.h
+++ b/qemu-timer.h
@@ -63,7 +63,6 @@ void qemu_run_timers(QEMUClock *clock);
void qemu_run_all_timers(void);
int qemu_alarm_pending(void);
void configure_alarms(char const *opt);
-int qemu_calculate_timeout(void);
void init_clocks(void);
int init_timer_alarm(void);
diff --git a/qemu-tool.c b/qemu-tool.c
index edb84f5..a0544d7 100644
--- a/qemu-tool.c
+++ b/qemu-tool.c
@@ -91,6 +91,10 @@ int qemu_init_main_loop(void)
return main_loop_init();
}
+void slirp_update_timeout(uint32_t *timeout)
+{
+}
+
void slirp_select_fill(int *pnfds, fd_set *readfds,
fd_set *writefds, fd_set *xfds)
{
diff --git a/slirp/libslirp.h b/slirp/libslirp.h
index 890fd86..77527ad 100644
--- a/slirp/libslirp.h
+++ b/slirp/libslirp.h
@@ -15,6 +15,7 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
struct in_addr vnameserver, void *opaque);
void slirp_cleanup(Slirp *slirp);
+void slirp_update_timeout(uint32_t *timeout);
void slirp_select_fill(int *pnfds,
fd_set *readfds, fd_set *writefds, fd_set *xfds);
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 1502830..90473eb 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -258,6 +258,13 @@ void slirp_cleanup(Slirp *slirp)
#define CONN_CANFRCV(so) (((so)->so_state &
(SS_FCANTRCVMORE|SS_ISFCONNECTED)) == SS_ISFCONNECTED)
#define UPD_NFDS(x) if (nfds < (x)) nfds = (x)
+void slirp_update_timeout(uint32_t *timeout)
+{
+ if (!QTAILQ_EMPTY(&slirp_instances)) {
+ *timeout = MIN(1000, *timeout);
+ }
+}
+
void slirp_select_fill(int *pnfds,
fd_set *readfds, fd_set *writefds, fd_set *xfds)
{
--
1.7.2.5