From d25f89c9e91d6c46b85969922411a211a6347a7d Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Fri, 17 Jun 2011 11:25:49 +0200 Subject: Register Linux dyntick timer as per-thread signal Derived from kvm-tool patch http://thread.gmane.org/gmane.comp.emulators.kvm.devel/74309 Ingo Molnar pointed out that sending the timer signal to the whole process, just blocking it everywhere, is suboptimal with an increasing number of threads. QEMU is also using this pattern so far. Linux provides a (non-portable) way to restrict the signal to a single thread: We can use SIGEV_THREAD_ID unless we are forced to emulate signalfd via an additional thread. That case could theoretically be optimized as well, but it doesn't look worth bothering. Reviewed-by: Richard Henderson Signed-off-by: Jan Kiszka Signed-off-by: Anthony Liguori --- compatfd.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'compatfd.c') diff --git a/compatfd.c b/compatfd.c index 41586ce..31654c6 100644 --- a/compatfd.c +++ b/compatfd.c @@ -115,3 +115,14 @@ int qemu_signalfd(const sigset_t *mask) return qemu_signalfd_compat(mask); } + +bool qemu_signalfd_available(void) +{ +#ifdef CONFIG_SIGNALFD + errno = 0; + syscall(SYS_signalfd, -1, NULL, _NSIG / 8); + return errno != ENOSYS; +#else + return false; +#endif +} -- cgit v1.1