> -----Original Message----- > From: penberg@xxxxxxxxx [mailto:penberg@xxxxxxxxx] On Behalf Of ext > Pekka Enberg > Sent: 19 January, 2012 13:08 ... > > 1. rename this API from low_mem_pressure to something more related to > > notification and memory situation in system: memory_pressure, > > memnotify, memory_level etc. The word "low" is misleading here > > The thing is called vmevent: Yes, I see it. But I was a bit confused with vmnotify_fops and was sure it is mapped through dev. Now it anonymous inode. > > On Thu, Jan 19, 2012 at 12:53 PM, <leonid.moiseichuk@xxxxxxxxx> wrote: > > 2. API must use deferred timers to prevent use-time impact. Deferred > > timer will be triggered only in case HW event or non-deferrable timer, > > so if device sleeps timer might be skipped and that is what expected > > for user-space > > I'm currently looking at the possibility of hooking VM events to perf which > also uses hrtimers. Can't we make hrtimers do the right thing? I had no answer for this question. According to hrtimer_cpu_notify the cpu state is tracked but timer may set HW event to wake up. In this case use-time will be affected due to you will have too much HW events and reasons to wakeup. At least powertop reports hrtimers in relation to <kernel core> as an activities sources. > > On Thu, Jan 19, 2012 at 12:53 PM, <leonid.moiseichuk@xxxxxxxxx> wrote: > > 3. API should be tunable for propagate changes when level is Up or > > Down, maybe both ways. > > Agreed. > > On Thu, Jan 19, 2012 at 12:53 PM, <leonid.moiseichuk@xxxxxxxxx> wrote: > > 4. to avoid triggering too much events probably has sense to filter > > according to amount of change but that is optional. If subscriber set > > timer to 1s the amount of events should not be very big. > > Agreed. > > On Thu, Jan 19, 2012 at 12:53 PM, <leonid.moiseichuk@xxxxxxxxx> wrote: > > 5. API must provide interface to request parameters e.g. available > > swap or free memory just to have some base. > > The current ABI already supports that. You can specify which attributes > you're interested in and they will be delivered as part of th event. But you have in vmnotify.h suspicious free_pages_threshold field. > > On Thu, Jan 19, 2012 at 12:53 PM, <leonid.moiseichuk@xxxxxxxxx> wrote: > > 6. I do not understand how work with attributes performed ( ) but it > > has sense to use mask and fill requested attributes using mask and > > callback table i.e. if free pages requested - they are reported, otherwise > not. > > That's how it works now in the git tree. Vmnotify.c has vmnotify_watch_event which collects fixed set of parameters. > I'm currently looking at how to support Minchan's non-sampled events. It > seems to me integrating with perf would be nice because we could simply > use tracepoints for this. If tracepoints not jeopardize use time has sense to do it. > > Pekka -- 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