Freitag, 16. August 2013

HP N54L Microserver - energy efficiency and power management

I recently worked on activating power management functions, reduce energy consumption and noise of my little HP N54L "toy". During this process I tried to avoid the usage of /etc/rc.local and set things by udev, hdparm and friends. Below are my results.

Actual results

With the following steps my system (N54L + 3xWD20EFRX HDD +1xWD5003AZEX HDD + LCD-mod + case fan mod + Debian Wheezy) uses 27W in idle mode. The USB W-LAN card uses another 10W. In active mode, e.g. compiling source code, the system runs (and boots) with around 57W. The highest power consumption observed is during startup phase with 88W.

First things first

For the following steps it might be necessary to have some packages installed, that maybe do not occur in this post. If I missed something, I appreciate a hint. Further the following steps might produce even better results with a custom kernel. I'm using the stock linux-image-3.2.0-4-amd64 kernel image as the time of writing and I have these packages installed: amd64-microcode, firmware-linux, firmware-linux-free, firmware-linux-nonfree and firmware-atheros (the latter for my WLAN card).

ASPM and ACPI

First I enabled PCIE ASPM in my (non-modded) BIOS and forced it together with ACPI via grub by changing GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub so it looks like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force pcie_aspm=force nmi_watchdog=0"

ASPM has now been enabled as lspci prooves:

00:04.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (PCIE port 0) (prog-if 00 [Normal decode])
[..]
                LnkCap: Port #1, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <64ns, L1 <1us
                        ClockPM- Surprise- LLActRep+ BwNot+
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
[..]
00:06.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780 PCI to PCI bridge (PCIE port 2) (prog-if 00 [Normal decode])
[..]
                LnkCap: Port #3, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <64ns, L1 <1us
                        ClockPM- Surprise- LLActRep+ BwNot+
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
02:00.0 USB controller: Renesas Technology Corp. uPD720201 USB 3.0 Host Controller (rev 03) (prog-if 30 [XHCI])
[..]
                LnkCap: Port #0, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <4us, L1 unlimited
                        ClockPM+ Surprise- LLActRep- BwNot-
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
[..]
03:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5723 Gigabit Ethernet PCIe (rev 10)
[..]
                LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <64us
                        ClockPM+ Surprise- LLActRep- BwNot-
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
[..]

Even so /sys/module/pcie_aspm/parameters/policy will still show as below:

[default] performance powersave

I'll show how to set the powersave value in /sys/module/pcie_aspm/parameters/policy in the next section.

JFTR: These are my ACPI related packages installed: acpi, acpid, acpi-support and acpi-support-base.

Enable powersaving via UDEV

The following rules file /etc/udev/rules.d/90-local-n54l.rules has been inspired by a blog post. It enables powersaving modes for all PCI, SCSI and USB devices and ASPM. Further the internal RADEON cards power profile is set to the low value. There is no monitor connected usually. The file contains these rules:

SUBSYSTEM=="module", KERNEL=="pcie_aspm", ACTION=="add", TEST=="parameters/policy", ATTR{parameters/policy}="powersave"

SUBSYSTEM=="i2c", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="pci", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="usb", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="usb", ACTION=="add", TEST=="power/autosuspend", ATTR{power/autosuspend}="2"
SUBSYSTEM=="scsi", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="spi", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"

SUBSYSTEM=="drm", KERNEL=="card*", ACTION=="add", DRIVERS=="radeon", TEST=="power/control", TEST=="device/power_method", ATTR{device/power_method}="profile", ATTR{device/power_profile}="low"

SUBSYSTEM=="scsi_host", KERNEL=="host*", ACTION=="add", TEST=="link_power_management_policy", ATTR{link_power_management_policy}="min_power"

Set harddrives spindown timeout

I decided to sent my system drive to standby after 20 minutes and the RAID drives after 15 minutes. This is usually ok, because the RAID isn't always used. hdparm is the right tool to realize this. Many people use the /dev/disk/by-uuid/... syntax here, to avoid having to touch the configuration file if some system configuration changes. Because I'm running a RAID, I couldn't use this syntax, although it might be possible to use /dev/disk/by-id/... instead. Well for the moment I stay with the configuration below. The relevant part of /etc/hdparm.conf is:

[..]

# system harddrive
/dev/sda {
        spindown_time = 240
}

# below are the WD20EFRX drives
/dev/sdb {
        spindown_time = 180
}

/dev/sdc {
        spindown_time = 180
}

/dev/sdd {
        spindown_time = 180
}

Idle mode

When there is nothing to do for the system, all I hear is the (still a bit noisy) fan of the power supply, which I might replace in the future too. Either by testing a different fan or by replacing the whole power supply unit by the fanless FORTRON FSP150-50TNF or (even better) a picoPSU.

The system currently shows a power consumption of around 37W in idle mode whereas the USB W-LAN card itself needs around 10W. There is a possibility to enable power savings mode for this card too. I could add this entry to /etc/udev/rules.d/90-local-n54l.rules:

SUBSYSTEM=="net", ACTION=="add", KERNEL=="wlan*" RUN+="/usr/bin/iw dev %k set power_save on"

But it turned out that the connection became a bit unstable after it. So I don't use this rule.

More on the road

There are a lot more options one can easily find via $search_engine. The N54L system could be brought to sleep and woken up by LAN via Wake-on-LAN (WOL). This is a feature I don't use. I've also read rumors about enabling different sleep/suspend states of the system, which seems to require to install a modded BIOS. Well, I'll post news and changes if they happen to come;)

Kommentare:

  1. Thanks for sharing, can you please share what was the previous power consumption before the tune?

    Thanks,
    Rodrigo

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    1. From running a very quick test it would be around 50 W in idle mode (probably 40 W without the USB W-LAN card).

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    2. That is a nice improvement. I have an older model (36L) that it is supposed to consume less than the 54L. I'll apply your setup to my model to save some €. Thanks again!

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  2. By idle, do you mean when then drives are spun down? I just measured power consumption on the n54l running freenas 9, 5x4tb 7,2krpm, 1x40gb ssd, and I got 80w "idle" when disks are still spinning. And that is with no extra peripherals such as wlan.

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    1. Yes, with idle I mean drives spun down (whereas the system drive usually doesn't spin down). As I reported: the highest power consumption was observed during startup and it was at around 88W, which is pretty near to your measured value.

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  3. Mats Lundqvist10. Januar 2014 10:03

    What is your consumption with all drives spinning? I'm probably going to be conservative with the spin down setting as to prolong the service life of the drives.

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    1. According to the WD specs, the drives use 4.1W (read/write), 3.0W (idle) and 0.4W (sleep). So you better add 12W for the harddrives alone + some power used of the system. Probably it would be 50..60W.

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  4. Hi Daniel,

    I was wondering if you have come to using a PicoPSU in replacement of the original PSU? What power consumption do you see then?

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