Commit cd758dd0 authored by Alex Bligh's avatar Alex Bligh Committed by Stefan Hajnoczi

aio / timers: Add prctl(PR_SET_TIMERSLACK, 1, ...) to reduce timer slack

Where supported, called prctl(PR_SET_TIMERSLACK, 1, ...) to
set one nanosecond timer slack to increase precision of timer
calls.
Signed-off-by: default avatarAlex Bligh <alex@alex.org.uk>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 4e0c6529
......@@ -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
......
......@@ -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)
......
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