diff mbox

[RFC,PATCHv10,06/31] aio / timers: Add prctl(PR_SET_TIMERSLACK, 1, ...) to reduce timer slack

Message ID 1376239405-4084-7-git-send-email-alex@alex.org.uk
State New
Headers show

Commit Message

Alex Bligh Aug. 11, 2013, 4:43 p.m. UTC 
Where supported, called prctl(PR_SET_TIMERSLACK, 1, ...) to
set one nanosecond timer slack to increase precision of timer
calls.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
---
 configure    |   18 ++++++++++++++++++
 qemu-timer.c |    7 +++++++
 2 files changed, 25 insertions(+)
diff mbox

Patch

diff --git a/configure b/configure
index 5659412..0a55c20 100755
--- a/configure
+++ b/configure
@@ -2834,6 +2834,21 @@  if compile_prog "" "" ; then
   ppoll=yes
 fi
 
+# check for prctl(PR_SET_TIMERSLACK , ... ) support
+prctl_pr_set_timerslack=no
+cat > $TMPC << EOF
+#include <sys/prctl.h>
+
+int main(void)
+{
+    prctl(PR_SET_TIMERSLACK, 1, 0, 0, 0);
+    return 0;
+}
+EOF
+if compile_prog "" "" ; then
+  prctl_pr_set_timerslack=yes
+fi
+
 # check for epoll support
 epoll=no
 cat > $TMPC << EOF
@@ -3833,6 +3848,9 @@  fi
 if test "$ppoll" = "yes" ; then
   echo "CONFIG_PPOLL=y" >> $config_host_mak
 fi
+if test "$prctl_pr_set_timerslack" = "yes" ; then
+  echo "CONFIG_PRCTL_PR_SET_TIMERSLACK=y" >> $config_host_mak
+fi
 if test "$epoll" = "yes" ; then
   echo "CONFIG_EPOLL=y" >> $config_host_mak
 fi
diff --git a/qemu-timer.c b/qemu-timer.c
index 4bf05d4..f224b62 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -41,6 +41,10 @@ 
 #include <poll.h>
 #endif
 
+#ifdef CONFIG_PRCTL_PR_SET_TIMERSLACK
+#include <sys/prctl.h>
+#endif
+
 /***********************************************************/
 /* timers */
 
@@ -507,6 +511,9 @@  void init_clocks(void)
         vm_clock = qemu_clock_new(QEMU_CLOCK_VIRTUAL);
         host_clock = qemu_clock_new(QEMU_CLOCK_HOST);
     }
+#ifdef CONFIG_PRCTL_PR_SET_TIMERSLACK
+    prctl(PR_SET_TIMERSLACK, 1, 0, 0, 0);
+#endif
 }
 
 uint64_t timer_expire_time_ns(QEMUTimer *ts)