Gleb Natapov <gleb@xxxxxxxxxx> wrote on 27/11/2013 11:21:59 AM: > On Wed, Nov 27, 2013 at 11:18:26AM +0200, Abel Gordon wrote: > > > > > > Gleb Natapov <gleb@xxxxxxxxxx> wrote on 27/11/2013 09:35:01 AM: > > > > > On Wed, Nov 27, 2013 at 10:49:20AM +0800, Jason Wang wrote: > > > > > 4. vhost statistics > > > > > This patch introduces a set of statistics to monitor different > > > performance > > > > > metrics of vhost and our polling and I/O scheduling mechanisms. The > > > > > statistics are exposed using debugfs and can be easily displayed with > > a > > > > > Python script (vhost_stat, based on the old kvm_stats) > > > > > https://github.com/abelg/virtual_io_acceleration/commit/ > > > ac14206ea56939ecc3608dc5f978b86fa322e7b0 > > > > > > > > How about using trace points instead? Besides statistics, it can also > > > > help more in debugging. > > > Definitely. kvm_stats has moved to ftrace long time ago. > > > > > > > We should use trace points for debugging information but IMHO we should > > have a dedicated (and different) mechanism to expose data that can be > > easily consumed by a user-space (policy) application to control how many > > vhost threads we need or any other vhost feature we may introduce > > (e.g. polling). That's why we proposed something like vhost_stat > > based on sysfs. > > > > This is not like kvm_stat that can be replaced with tracepoints. Here > > we will like to expose data to "control" the system. So I would > > say what we are trying to do something that resembles the ksm interface > > implemented under /sys/kernel/mm/ksm/ > There are control operation and there are performance/statistic > gathering operations use /sys for former and ftrace for later. The fact > that you need /sys interface for other things does not mean you can > abuse it for statistics too. Agree. Any statistics that we add for debugging purposes should be implemented using tracepoints. But control and related data interfaces (that are not for debugging purposes) should be in sysfs. Look for example at /sys/kernel/mm/ksm/full_scans /sys/kernel/mm/ksm/pages_shared /sys/kernel/mm/ksm/pages_sharing /sys/kernel/mm/ksm/pages_to_scan /sys/kernel/mm/ksm/pages_unshared /sys/kernel/mm/ksm/pages_volatile -- 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
