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[Qemu-devel] [PATCH] Use SIGIO in Linux host
From: |
Anders Melchiorsen |
Subject: |
[Qemu-devel] [PATCH] Use SIGIO in Linux host |
Date: |
Sun, 20 Apr 2008 11:20:29 +0200 |
Network packets coming over TAP have a latency that is
dictated by the periodic timer. That can hurt performance.
This patch activates signals for fds that are being used
with select(), giving predictable latency.
Signed-off-by: Anders Melchiorsen <address@hidden>
diff --git a/vl.c b/vl.c
index ad4f6ef..eb2a75e 100644
--- a/vl.c
+++ b/vl.c
@@ -1149,6 +1149,25 @@ static int timer_load(QEMUFile *f, void *opaque, int
version_id)
return 0;
}
+#if defined(__linux__)
+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)
@@ -1241,6 +1260,19 @@ static uint64_t qemu_next_deadline(void)
#define RTC_FREQ 1024
+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|O_NONBLOCK);
+ fcntl(fd, F_SETOWN, getpid());
+}
+
static void enable_sigalrm(int fd)
{
struct sigaction act;
@@ -5530,6 +5562,10 @@ int qemu_set_fd_handler2(int fd,
return -1;
ioh->next = first_io_handler;
first_io_handler = ioh;
+#if defined(__linux__)
+ enable_sigio(fd);
+#endif
+
found:
ioh->fd = fd;
ioh->fd_read_poll = fd_read_poll;
--
1.5.2.5