On Fri, Mar 20, 2015 at 12:15:15PM +0100, Alexander Graf wrote: > > > On 20.03.15 10:39, Paul Mackerras wrote: > > This reads the timebase at various points in the real-mode guest > > entry/exit code and uses that to accumulate total, minimum and > > maximum time spent in those parts of the code. Currently these > > times are accumulated per vcpu in 5 parts of the code: > > > > * rm_entry - time taken from the start of kvmppc_hv_entry() until > > just before entering the guest. > > * rm_intr - time from when we take a hypervisor interrupt in the > > guest until we either re-enter the guest or decide to exit to the > > host. This includes time spent handling hcalls in real mode. > > * rm_exit - time from when we decide to exit the guest until the > > return from kvmppc_hv_entry(). > > * guest - time spend in the guest > > * cede - time spent napping in real mode due to an H_CEDE hcall > > while other threads in the same vcore are active. > > > > These times are exposed in debugfs in a directory per vcpu that > > contains a file called "timings". This file contains one line for > > each of the 5 timings above, with the name followed by a colon and > > 4 numbers, which are the count (number of times the code has been > > executed), the total time, the minimum time, and the maximum time, > > all in nanoseconds. > > > > Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx> > > Have you measure the additional overhead this brings? I haven't - in fact I did this patch so I could measure the overhead or improvement from other changes I did, but it doesn't measure its own overhead, of course. I guess I need a workload that does a defined number of guest entries and exits and measure how fast it runs with and without the patch (maybe something like H_SET_MODE in a loop). I'll figure something out and post the results. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
