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Is PowerTop / TLP Still Useful To Save Power On Linux Laptops?

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  • #11
    I find if I set all the options to Good blindly then my USB mouse goes to sleep constantly and only wakes up if I click a button

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    • #12
      My APM [version 5.6] will give better results than TLP and Powertop [settings], and this in terms of energy saving [bat] and performance [ac] - for Ubuntu and derivatives.

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      • #13
        I stopped installing these some years ago when the "autosuspend device" feature put the USB and Ethernet ports on my Lenovo laptop to sleep, but they never woke up again... the hardware was damaged. From my research, this seems to be the major power saving feature of TLP and Powertop and it is not recommend in the official kernel documentation. From https://www.kernel.org/doc/Documenta...management.txt

        Warnings
        -------- The USB specification states that all USB devices must support power management. Nevertheless, the sad fact is that many devices do not support it very well. You can suspend them all right, but when you try to resume them they disconnect themselves from the USB bus or they stop working entirely. This seems to be especially prevalent among printers and scanners, but plenty of other types of device have the same deficiency. For this reason, by default the kernel disables autosuspend (the power/control attribute is initialized to "on") for all devices other than hubs. Hubs, at least, appear to be reasonably well-behaved in this regard. (In 2.6.21 and 2.6.22 this wasn't the case. Autosuspend was enabled by default for almost all USB devices. A number of people experienced problems as a result.) This means that non-hub devices won't be autosuspended unless the user or a program explicitly enables it. As of this writing there aren't any widespread programs which will do this; we hope that in the near future device managers such as HAL will take on this added responsibility. In the meantime you can always carry out the necessary operations by hand or add them to a udev script. You can also change the idle-delay time; 2 seconds is not the best choice for every device. If a driver knows that its device has proper suspend/resume support, it can enable autosuspend all by itself. For example, the video driver for a laptop's webcam might do this (in recent kernels they do), since these devices are rarely used and so should normally be autosuspended. Sometimes it turns out that even when a device does work okay with autosuspend there are still problems. For example, the usbhid driver, which manages keyboards and mice, has autosuspend support. Tests with a number of keyboards show that typing on a suspended keyboard, while causing the keyboard to do a remote wakeup all right, will nonetheless frequently result in lost keystrokes. Tests with mice show that some of them will issue a remote-wakeup request in response to button presses but not to motion, and some in response to neither. The kernel will not prevent you from enabling autosuspend on devices that can't handle it. It is even possible in theory to damage a device by suspending it at the wrong time. (Highly unlikely, but possible.) Take care.
        Last edited by teresaejunior; 11 December 2017, 08:33 PM.

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        • #14
          Michael the TLP test setup, is the updated kernel + TLP, not updated kernel + powertop + TLP, right?

          Couldn't find out the answer reading the blog post

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          • #15
            If your Broadwell hardare is, like mine, affected by the APLM sata bug, then the fix in 4.15 git might account for a significant power savings, allowing the package to go into lower states than C2.

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            • #16
              Because I run my laptop (t540p) without drivers for the nV card, there is no automatic sleep for the discrete graphics. Using powertop to enable power management on it saves about 3 watts. Every other tuneable says good, save for a writeback timer, which I don't care about.

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              • #17
                Hi,

                Originally posted by kmare View Post
                hansdegoede thank you for your hard work! I'm already enjoying a good enough battery life on my laptop (ASUS zenbook pro UX501VW) on Fedora 27 with TLP and I certainly can't wait to see the improvements with Fedora 28.
                BTW, my laptop (among many others with a similar setup) is a hybrid one, intel+nvidia. Booting Fedora on it, would result in a lock up / freeze unless I add
                Code:
                acpi_osi=! acpi_osi=Windows 2009
                as kernel parameters ( https://github.com/Bumblebee-Project...bee/issues/764 ). I know the same is needed for many other similar laptops. Is there something that could be done to make it automatic or something? Not every user is in the position to know that or even "fix" it.
                And yeah, I so wish my laptop didn't include an Nvidia card at all :/
                Yes this is a known and very nasty issue. Unfortunately many knowledgeable people have already looked at this and no-one has found a fix so far. As for automatically enabling the magic commandline options that is theoretically possible, but requires adding a long list of models for this and more importantly these magic options don't work on all hardware which suffers from this. The
                Code:
                acpi_osi=! acpi_osi=Windows 2009
                workaround relies on the BIOS tables having separate code paths for Windows XP (IIRC) which not all models have, there are laptop models without the necessary BIOS code for this and the workaround does not work there, so we really need a proper fix.

                Regards,

                Hans

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                • #18
                  Biggest savings on current Intel Core-i CPUs come from SATA link power management keeping the whole CPU package awake: https://www.youtube.com/watch?v=bMkrYFaplso
                  Last edited by rene; 12 December 2017, 04:41 AM.

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                  • #19
                    Originally posted by arbition View Post
                    Because I run my laptop (t540p) without drivers for the nV card, there is no automatic sleep for the discrete graphics. Using powertop to enable power management on it saves about 3 watts. Every other tuneable says good, save for a writeback timer, which I don't care about.
                    And what do you say about it? Although PowerTOP [overstates it - it will not show me the duration of the action longer than eg 10 h], it misrepresents because real consumption can go down to about 1.5 Watt. The time of operation of the Asus UX303LN under my solutions is about 10-12 h - editing documents + Internet [chrome].

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                    • #20
                      I use powertop (or the script I generated from it) on most of my boxes. (Desktop, thin client and laptop alike.) I wish, though, it would be a default that is set by the Linux kernel. Also, there are a few cases which misbehave, e.g. my Logi G5 mouse. If you switch energy saving on it actually goes off. Totally. You need to click to revive it, but after 5 seconds without movement (or clicks) it goes to deep sleep again. So I have to exclude it.
                      However I measured power savings at the wall (no precision device) roughly in the range of <5 - <1 Watt (usually 1-3, as far as I can tell). Well, for a TC that only pulls in the range of 7 W from the wall ~1 W is still good. Sometimes C6 sleep mode activated in BIOS yielded much more (10 - 12 W), but I got nasty SMD capacitor or coil whining on selected boards.
                      Stop TCPA, stupid software patents and corrupt politicians!

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