On Tue, 20 Mar 2012, Mike Snitzer wrote: > I once wanted to replace all msleep(1); with cpu_relax();: > http://www.redhat.com/archives/dm-devel/2010-September/msg00100.html > > But Alasdair wasn't sure if cpu_relax() would provide the required > delay effect: > https://www.redhat.com/archives/dm-devel/2011-June/msg00080.html cpu_relax() would basically kill the kernel if compiled without preempt. cpu_relax() makes the current processor sleep for a little moment, but it doesn't schedule a different process. cpu_relax() is useful in spinlocks - so that process waiting on a spinlock is not slowing down the other process on a CPU with hyperthreading. There was another possibility --- replace msleep(1) with yield(). The problem with yield() is that if the process has readltime priority and calls yield(), it doesn't give CPU to a different process with a lower priority. So it would cause deadlock if executed with realtime priority. msleep(1) doesn't have this problem, so it's the best. Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
