On Fri, Jun 18, 2010 at 12:56 AM, Len Brown <lenb@xxxxxxxxxx> wrote: > On Thu, 17 Jun 2010, Victor Lowther wrote: > >> > The idea here is to not require user-space to need updating >> > whenever a future knob is invented. We can do a great job >> > at documenting the past, but a poor job of documenting the future:-) >> >> Well, I would suggest that the habit of not documenting what is >> happening with power management in the kernel needs to change, then. > > Actually some of the knobs I showed in the examples > have been documented for *years*, yet are ignored > by user-space today. I don't want to insult user-space > programmers, but the reality is that simpler is usually better. Let me explain where I am coming from, then. I maintain pm-utils, one of the main low-level bodies of userspace code that concerns itself with power management. I am currently in the process of standardizing some of the more common power management tweaks so that they will work in a cross distro manner, and know from this that the documentation we have is badly fragmented -- if you know exactly what you are looking for, you can google or grep for it, but if you do not, there is no easy way to find a list of all the power management settings you can tune. >> Having the documentation and example code for how to tweak the various >> power management settings from userspace is inherently more flexible >> than trying to expose a single knob from the kernel to userspace for >> power management, with little loss of flexibility. > > Yes, the ultimate in flexibility is to update user-space whenever > some new driver or new knob appears in the kernel. I'm not proposing > that ability be taken away. I'm proposing that in many cases it > is unnecessary. I disagree. Most of userspace does not care about how the system is trying to save power. I maintain one that does, and I do not like the idea of adding another knob whose entire purpose is to map other, already existing knobs onto a line, especially when we can do that in userspace easily enough if anyone actually wants it. > The idea is to have the ability to add something to the > kernel and avoid the need to make any change to user-space. Userspace in this case consists mainly of acpi-scripts/pm-utils/laptop-mode-tools, upower, g-p-m/kpowersave/x-p-m, and X. I can only speak for pm-utils, but the model pm-utils, acpi-scripts, and laptop-mode-tools use does not map to your proposed knob at all. We use a two-state model -- either we are on AC power and use the kernel's default power state, or we are on battery power and set power management to a set of distro or user chosen set of parameters. I am working on making pm-utils contain some predefined powersaving policies, but I do not expect them to change the two-state model much more than changing which power management tweaks are used in the on-ac and on-battery states. > thanks, > -Len Brown, Intel Open Source Technology Center > _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
