Messages in this thread | | | Date | Fri, 28 Jun 2013 11:45:47 -0700 | From | Anton Vorontsov <> | Subject | Re: [PATCH v2] vmpressure: implement strict mode |
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On Fri, Jun 28, 2013 at 02:25:58PM -0400, Luiz Capitulino wrote: > > > > That's how it's expected to work, because on strict mode you're notified > > > > for the level you registered for. So apps registering for critical, will > > > > still be notified on critical just like before. > > > > > > Suppose you introduce a new level, and the system hits this level. Before, > > > the app would receive at least some notification for the given memory load > > > (i.e. one of the old levels), with the new level introduced in the kernel, > > > the app will receive no events at all. > > That's not true. If an app registered for critical it will still get > critical notification when the system is at the critical level. Just as it > always did. No new events will change this. > > With today's semantics though, new events will change when current events > are triggered. So each new extension will cause applications to have > different behaviors, in different kernel versions. This looks quite > undesirable to me.
I'll try to explain it again.
Old behaviour:
low -> event x <- but the system is at this unnamed level, between low and med med crit
We add a level:
low low-med <- system at this state, we send an event, but the old app does not know about it, so it won't receive *any* notifications. (In older kernels it would receive low level notification med crit
You really don't see a problem here?
I see the problem, and I see these solutions:
1. Use current scheme. 2. Add versioning. 3. Never change the levels (how can we know?)
Anton
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