Messages in this thread | | | Subject | Re: [PATCH] Add possibility to set /dev/tty number | From | "Austin S. Hemmelgarn" <> | Date | Tue, 5 Jan 2016 08:16:52 -0500 |
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On 2016-01-04 17:55, One Thousand Gnomes wrote: >>> If the console isn't initialized by userspace, is any of that space >>> still really being used? Have you tried that? >> I'm pretty certain that most of the space that gets taken up by the >> scrollback buffer and screen isn't directly used unless the console is >> used, but there are still structures that get allocated at driver >> instantiation for each VT, including the device structures and such. > > So fix that instead. I never said that it was broken, I was just pointing out that the overhead is non-zero even when the VT is unused. > > And really for low memory embedded why do you even have the VT layer in > your system in the first place ? Sometimes this is unavoidable. Any kind of generic system generally wants the VT layer, and there are a number of low memory embedded systems that I've seen that depend on the ability to switch VT's for their software to work correctly. > >>> If we remove the number of devices, those "broken" userspace programs >>> will also break, so that implies that we should not allow this change. >> No, the software should just need to be recompiled (I've tested this >> with ConsoleKit, which also fails gracefully when it tires to open a tty >> device that doesn't exist), or adapted to dynamically detect the number >> of TTYs (like it should have in the first place for portability reasons). > > We don't do regressions. Requiring only a recompilation isn't a regression, especially when it works fine without being recompiled, and I have yet to actually see anything that changing the number of VT's would break other than ConsoleKit (systemd-logind might also need a rebuild, but I'm not sure about that, and don't have a system I could test it on). > >> device drivers). I doubt that it will work out to any more than 16k size >> difference, but that's still a few more pages (on most systems) that >> could be used for other things. > > And those embedded devices can almost certainly save more by just not > including the vt layer. And a few pages can make a difference on _any_ device, not just an embedded system. For a purpose specific system, that can be the difference between fitting the working set in memory and having to hit swap space.
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