On Fri, 28 Jun 2013 09:02:01 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote: > Hi Andrew, > > On Thu, Jun 27, 2013 at 03:02:31PM -0700, Andrew Morton wrote: > > On Wed, 26 Jun 2013 23:17:12 -0400 Luiz Capitulino <lcapitulino@xxxxxxxxxx> wrote: > > > > > Currently, an eventfd is notified for the level it's registered for > > > _plus_ higher levels. > > > > > > This is a problem if an application wants to implement different > > > actions for different levels. For example, an application might want > > > to release 10% of its cache on level low, 50% on medium and 100% on > > > critical. To do this, an application has to register a different > > > eventfd for each pressure level. However, fd low is always going to > > > be notified and and all fds are going to be notified on level critical. > > > > > > Strict mode solves this problem by strictly notifiying an eventfd > > > for the pressure level it registered for. This new mode is optional, > > > by default we still notify eventfds on higher levels too. > > > > > > > It didn't take long for this simple interface to start getting ugly :( > > And having the fd operate in different modes is ugly. > > > > Can we instead pass the level in the event payload? > > You mean userland have to look the result of read(2) to confirm what > current level is and if it's no interest for us, we don't do any reaction. Something like that. It's flexible, simple, keeps policy in userspace. > If so, userland daemon would receive lots of events which are no interest. "lots"? If vmpressure is generating events at such a high frequency that this matters then it's already busted? -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>