With the IO thread, shouldn't we be striving to perform the select()s
within the IO thread itself to completely avoid the need to use SIGIO at
all?
Regards,
Anthony Liguori
Marcelo Tosatti wrote:
From: Anders Melchiorsen [EMAIL PROTECTED]
Without I/O signals, qemu is relying on periodic timer events to poll
the I/O. That seems wrong, even though it works reasonably well
because timers are so frequent. In KVM, timers are less frequent, and
it does not work quite as well.
Here is a quick try at a more elaborate patch.
It attaches a signal to all[1] file descriptors that will be used in
select(). Also, it uses a dedicated SIGIO handler rather than
piggybacking on the alarm handler, so alarm I/O is changed to use
SIGALRM.
I copied the handler function from the alarm case, quite frankly I do
not quite understand what is going on. Also, I left _WIN32 out, since
I have no idea how signals work there.
[1] The slirp file descriptors are not included yet.
Index: kvm-userspace.io/qemu/vl.c
===
--- kvm-userspace.io.orig/qemu/vl.c
+++ kvm-userspace.io/qemu/vl.c
@@ -1177,6 +1177,25 @@ static int timer_load(QEMUFile *f, void
return 0;
}
+#ifndef _WIN32
+static void host_io_handler(int host_signum)
+{
+CPUState *env = next_cpu;
+
+if (env) {
+/* stop the currently executing cpu because io occured */
+cpu_interrupt(env, CPU_INTERRUPT_EXIT);
+#ifdef USE_KQEMU
+if (env-kqemu_enabled) {
+kqemu_cpu_interrupt(env);
+}
+#endif
+}
+
+event_pending = 1;
+}
+#endif
+
#ifdef _WIN32
void CALLBACK host_alarm_handler(UINT uTimerID, UINT uMsg,
DWORD_PTR dwUser, DWORD_PTR dw1, DWORD_PTR
dw2)
@@ -1270,7 +1289,20 @@ static uint64_t qemu_next_deadline(void)
#define RTC_FREQ 1024
-static void enable_sigio_timer(int fd)
+static void enable_sigio(int fd)
+{
+struct sigaction act;
+
+sigfillset(act.sa_mask);
+act.sa_flags = 0;
+act.sa_handler = host_io_handler;
+
+sigaction(SIGIO, act, NULL);
+fcntl(fd, F_SETFL, O_ASYNC);
+fcntl(fd, F_SETOWN, getpid());
+}
+
+static void enable_sigalrm(int fd)
{
struct sigaction act;
@@ -1279,8 +1311,9 @@ static void enable_sigio_timer(int fd)
act.sa_flags = 0;
act.sa_handler = host_alarm_handler;
-sigaction(SIGIO, act, NULL);
+sigaction(SIGALRM, act, NULL);
fcntl(fd, F_SETFL, O_ASYNC);
+fcntl(fd, F_SETSIG, SIGALRM);
fcntl(fd, F_SETOWN, getpid());
}
@@ -1317,7 +1350,7 @@ static int hpet_start_timer(struct qemu_
if (r 0)
goto fail;
-enable_sigio_timer(fd);
+enable_sigalrm(fd);
t-priv = (void *)(long)fd;
return 0;
@@ -1355,7 +1388,7 @@ static int rtc_start_timer(struct qemu_a
return -1;
}
-enable_sigio_timer(rtc_fd);
+enable_sigalrm(rtc_fd);
t-priv = (void *)(long)rtc_fd;
@@ -4029,7 +4062,6 @@ static TAPState *net_tap_fd_init(VLANSta
return NULL;
s-fd = fd;
s-no_poll = 0;
-enable_sigio_timer(fd);
s-vc = qemu_new_vlan_client(vlan, tap_receive, NULL, s);
qemu_set_fd_handler2(s-fd, tap_read_poll, tap_send, NULL, s);
snprintf(s-vc-info_str, sizeof(s-vc-info_str), tap: fd=%d, fd);
@@ -5661,6 +5693,10 @@ int qemu_set_fd_handler2(int fd,
return -1;
ioh-next = first_io_handler;
first_io_handler = ioh;
+#ifndef _WIN32
+enable_sigio(fd);
+#endif
+
found:
ioh-fd = fd;
ioh-fd_read_poll = fd_read_poll;
-
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