On Tue, May 8, 2012 at 10:50 AM, KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx> wrote: >>> 1) sample_period is brain damaged idea. If people ONLY need to >>> sampling stastics, they >>> only need to read /proc/vmstat periodically. just remove it and >>> implement push notification. >>> _IF_ someone need unfrequent level trigger, just use >>> "usleep(timeout); read(vmevent_fd)" >>> on userland code. >> >> That comes from a real-world requirement. See Leonid's email on the topic: >> >> https://lkml.org/lkml/2012/5/2/42 > > I know, many embedded guys prefer such timer interval. I also have an > experience > similar logic when I was TV box developer. but I must disagree. Someone hope > timer housekeeping complexity into kernel. but I haven't seen any > justification. Leonid? >>> 6) Also vmevent_event must hide from userland. >> >> Why? That's part of the ABI. > > Ahhh, if so, I missed something. as far as I look, vmevent_fd() only depend > on vmevent_config. which syscall depend on vmevent_evennt? read(2). See tools/testing/vmevent/vmevent-test.c for an example how the ABI is used. >>> 7) vmevent_config::size must be removed. In 20th century, M$ API >>> prefer to use this technique. But >>> They dropped the way because a lot of application don't initialize >>> size member and they can't use it for keeping upper compitibility. >> >> It's there to support forward/backward ABI compatibility like perf >> does. I'm going to keep it for now but I'm open to dropping it when >> the ABI is more mature. > > perf api is not intended to use from generic applications. then, I don't > think it will make abi issue. tool/perf is sane, isn't it? but vmevent_fd() > is generic api and we can't trust all userland guy have sane, unfortunately. The perf ABI is being used by other projects as well. We don't _depend_ on ->size being sane as much as use it to detect new features in the future. But anyway, we can consider dropping once the ABI is more stable. > Hm. If you want vmevent makes depend on CONFIG_EMBEDDED, I have no reason to > complain this feature. At that world, almost all applications _know_ their > system configuration. then I don't think api misuse issue is big matter. No, I don't want to do that. I was just commeting on why existing solutions are the way they are. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href