Hi, Just couple of observations, which maybe wrong below > -----Original Message----- > From: Pekka Enberg [mailto:penberg@xxxxxxxxx] On Behalf Of ext Pekka > Enberg > Sent: 17 January, 2012 20:51 .... > +struct vmnotify_config { > + /* > + * Size of the struct for ABI extensibility. > + */ > + __u32 size; > + > + /* > + * Notification type bitmask > + */ > + __u64 type; > + > + /* > + * Free memory threshold in percentages [1..99] > + */ > + __u32 free_threshold; Would be possible to not use percents for thesholds? Accounting in pages even not so difficult to user-space. Also, looking on vmnotify_match I understand that events propagated to user-space only in case threshold trigger change state from 0 to 1 but not back, 1-> 0 is very useful event as well. Would be possible to use for threshold pointed value(s) e.g. according to enum zone_state_item, because kinds of memory to track could be different? E.g. to tracking paging activity NR_ACTIVE_ANON and NR_ACTIVE_FILE could be interesting, not only free. > + > + /* > + * Sample period in nanoseconds > + */ > + __u64 sample_period_ns; > +}; > + .... > +struct vmnotify_event { > + /* Size of the struct for ABI extensibility. */ > + __u32 size; > + > + __u64 nr_avail_pages; > + > + __u64 nr_swap_pages; > + > + __u64 nr_free_pages; > +}; Two fields here most likely session-constant, (nr_avail_pages and nr_swap_pages), seems not much sense to report them in every event. If we have memory/swap hotplug user-space can use sysinfo() call. > +static void vmnotify_sample(struct vmnotify_watch *watch) { ... > + si_meminfo(&si); > + event.nr_avail_pages = si.totalram; > + > +#ifdef CONFIG_SWAP > + si_swapinfo(&si); > + event.nr_swap_pages = si.totalswap; > +#endif > + Why not to use global_page_state() directly? si_meminfo() and especial si_swapinfo are quite expensive call. > +static void vmnotify_start_timer(struct vmnotify_watch *watch) { > + u64 sample_period = watch->config.sample_period_ns; > + > + hrtimer_init(&watch->timer, CLOCK_MONOTONIC, > HRTIMER_MODE_REL); > + watch->timer.function = vmnotify_timer_fn; > + > + hrtimer_start(&watch->timer, ns_to_ktime(sample_period), > +HRTIMER_MODE_REL_PINNED); } Do I understand correct you allocate timer for every user-space client and propagate events every pointed interval? What will happened with system if we have a timer but need to turn CPU off? The timer must not be a reason to wakeup if user-space is sleeping. -- 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