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Poll main loop after I/O events were received

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Polling until select returns empty fdsets helps to reduce the switches
between iothread and vcpus. The benefit of this patch is best visible
when running an SMP guest on an SMP host in emulation mode.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Jan Kiszka 2011-08-22 17:46:02 +02:00 committed by Anthony Liguori
parent 200668ba08
commit c9f711a5d3
2 changed files with 9 additions and 5 deletions
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2
sysemu.h
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@ -67,7 +67,7 @@ void do_info_snapshots(Monitor *mon);
void qemu_announce_self(void);
void main_loop_wait(int nonblocking);
int main_loop_wait(int nonblocking);
bool qemu_savevm_state_blocked(Monitor *mon);
int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,

12
vl.c
View File

@ -1321,7 +1321,7 @@ void qemu_system_vmstop_request(int reason)
qemu_notify_event();
}
void main_loop_wait(int nonblocking)
int main_loop_wait(int nonblocking)
{
fd_set rfds, wfds, xfds;
int ret, nfds;
@ -1368,6 +1368,7 @@ void main_loop_wait(int nonblocking)
them. */
qemu_bh_poll();
return ret;
}
#ifndef CONFIG_IOTHREAD
@ -1385,7 +1386,8 @@ qemu_irq qemu_system_powerdown;
static void main_loop(void)
{
bool nonblocking = false;
bool nonblocking;
int last_io __attribute__ ((unused)) = 0;
#ifdef CONFIG_PROFILER
int64_t ti;
#endif
@ -1394,7 +1396,9 @@ static void main_loop(void)
qemu_main_loop_start();
for (;;) {
#ifndef CONFIG_IOTHREAD
#ifdef CONFIG_IOTHREAD
nonblocking = !kvm_enabled() && last_io > 0;
#else
nonblocking = cpu_exec_all();
if (vm_request_pending()) {
nonblocking = true;
@ -1403,7 +1407,7 @@ static void main_loop(void)
#ifdef CONFIG_PROFILER
ti = profile_getclock();
#endif
main_loop_wait(nonblocking);
last_io = main_loop_wait(nonblocking);
#ifdef CONFIG_PROFILER
dev_time += profile_getclock() - ti;
#endif