# Very low performance on HP Compaq 6715b

## BB_DaKraxor

Hello,

I've been trying to install Gentoo on my new HP Compaq 6715b laptop all night. Booting from the Live CD goes fine, I've done every single steps I read in the instructions, I've been able to compile my kernel and boot it. However, booting was very slow so I run hdparm -Tt /dev/sda to find out the reading speed is about ~100kB/s. When booting from the Live CD the same test results approx. 38MB/s. I googled a LOT with a little success: with kernel option pci=nomsi I could get a 3 to 5 times better test result (300-500kB/s), so now booting takes only about 2 minutes. What a relief, huh?

Is there any way to see the differences between the Live CD kernel and my hand-compiled one? 

lspci tells me that my hard disk is ATI SB600 Non-Raid-5 SATA, I'm using the kernel driver AHCI.

Any ideas to reach the performance of the Live CD?

ThanksLast edited by BB_DaKraxor on Tue Nov 25, 2008 9:47 pm; edited 1 time in total

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## nixnut

Moved from Installing Gentoo to Kernel & Hardware.

Postinstallation problem, so moved here.

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## eccerr0r

try comparing /proc/config* of the livecd with your .config file, have ACPI, PCI, and all working?

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## BB_DaKraxor

Sorry for posting to the wrong forum and thanks for the reply.

What should I look for?

I see that lots of SATA drivers are compiled as modules on the live CD, but if I use the same settings, I can't boot my kernel because it doesn't find my hard disk at all. I think that's because modules are loaded after mounting the root file system. I don't really understand how the live CD boots, but I have to compile the AHCI SATA driver into the kernel to be able to boot.

Is it possible that something else in my kernel conflicts with the SATA driver? If it is, then how do I find out what?

At the moment I don't really care about APCI and other features to work, that will be another issue, I would like to have a kernel that can handle my SATA hard disk, that's all.

(By the way, I've successfully installed a Debian linux, it's running fine, nice hdparm test results but no ACPI, Bluetooth, Wi-Fi, etc. support, so I'm still at the same problem: I have to compile my own kernel... As soon as I get a working kernel, I'll go back to Gentoo for sure.)

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## eccerr0r

Right, the livecd actually uses a "initrd" that includes all the modules.  You could use genkernel to build a kernel as well.

Usually really crappy operation occurs when you're doing PIO to the disk.  See if you can get a bootable kernel without "generic" SATA support, forcing it to use customized, DMA support?  And make sure you have all legacy ATA software support disabled even though it may say something about SATA disks.

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## BB_DaKraxor

In case someone finds this topic with the same or related question, or even better, an actual solution:

According to this mailing list, HP Compaq 6715b has (and most likely other HP products also have) a BIOS bug that makes APCI screw things up, slowing down the performance to the point where you can hardly use a terminal. So the problem - in my understanding - is most likely not related to the SATA driver or anything like that.

I've found 2 so-called workarounds:

- If you use a 64-bit distro, ACPI works fine. On the other hand, for this particular laptop (or perhaps more), none of the available graphics drivers provide direct rendering - disabling you to play games and such. Please correct me if I'm wrong! If anyone has been able to make direct rendering work with ATI Radeon X1250 on 64-bit linux, please tell me!

- You can of course disable ACPI by passing the acpi=off option to the kernel when booting.

Please, if you've been more successful than me, tell me!

Best wishes, BB_DaKraxor.

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