On 04/30/2012 05:01 PM, Pekka Enberg wrote: > Hi Minchan, > > On Mon, Apr 30, 2012 at 10:52 AM, Minchan Kim <minchan@xxxxxxxxxx> wrote: >>> It makes the userspace side simpler for "lowmem notification" use >>> case. I'm open to changing the ABI if it doesn't make the userspace >>> side too complex. >> >> Yes. I understand your point but if we still consider all of values, >> we don't have any way to capture exact values except triggered event value. >> I mean there is no lock to keep consistency. >> If stale data is okay, no problem but IMHO, it could make user very confusing. >> So let's return value for first matched event if various event match. >> Of course, let's write down it in ABI. >> If there is other idea for reporting all of item with consistent, I'm okay. > > What kind of consistency guarantees do you mean? The data sent to > userspace is always a snapshot of the state and therefore can be stale > by the time it reaches userspace. Consistency between component of snapshot. let's assume following as 1. User expect some events's value would be minus when event he expect happen. A : -3, B : -4, C : -5, D : -6 2. Logically, it's not possible to mix plus and minus values for the events. A : -3, B : -4, C : -5, D : -6 ( O ) A : -3, B : -4, C : 1, D : 2 ( X ) But in current implementation, some of those could be minus and some of those could be plus. Which event could user believe? At least, we need a _captured_ value when event triggered so that user can ignore other values. > > If your code needs stricter consistency guarantees, you probably want > to do it in the kernel. > > 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- Kind regards, Minchan Kim -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>