On Fri, 28 Jun 2013 11:55:47 -0700 Anton Vorontsov <anton@xxxxxxxxxx> wrote: > On Fri, Jun 28, 2013 at 02:45:07PM -0400, Luiz Capitulino wrote: > > On Fri, 28 Jun 2013 10:09:17 -0700 > > Anton Vorontsov <anton@xxxxxxxxxx> wrote: > > > > > So, I would now argue that the current scheme is perfectly OK and can do > > > everything you can do with the "strict" one, > > > > I forgot commenting this bit. This is not true, because I don't want a > > low fd to be notified on critical level. The current interface just > > can't do that. > > Why can't you use poll() and demultiplex the events? Check if there is an > event in the crit fd, and if there is, then just ignore all the rest. This may be a valid workaround for current kernels, but application behavior will be different among kernels with a different number of events. Say, we events on top of critical. Then crit fd will now be notified for cases where it didn't use to on older kernels. > > However, it *is* possible to make non-strict work on strict if we make > > strict default _and_ make reads on memory.pressure_level return > > available events. Just do this on app initialization: > > > > for each event in memory.pressure_level; do > > /* register eventfd to be notified on "event" */ > > done > > This scheme registers "all" events. Yes, because I thought that's the user-case that matters for activity manager :) > Here is more complicated case: > > Old kernels, pressure_level reads: > > low, med, crit > > The app just wants to listen for med level. > > New kernels, pressure_level reads: > > low, FOO, med, BAR, crit > > How would application decide which of FOO and BAR are ex-med levels? What you meant by ex-med? Let's not over-design. I agree that allowing the API to be extended is a good thing, but we shouldn't give complex meaning to events, otherwise we're better with a numeric scale instead. -- 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>