AHCI HDD access destroys performance

mattsavigear

I have a couple of machines, one Intel quad-core desktop and one dual-core laptop. For some time now (I'm not sure if it corresponds to a kernel upgrade, but it's been a problem for months), both machines have suffered from massive performance drop-off when accessing the disk. For example, when unzipping the large distribution file for netbeans, pretty much everything else freezes down to page refreshes in Firefox.

Both machines are running ~AMD64 and have SATA drives set up for AHCI access. The laptop is running 2.6.27-gentoo-r4 and the desktop is on 2.6.30-gentoo-r1. I'm finding that my 'old' 3.2GHz P4 machine is actually more responsive to use than these more recent machines (though I'm just moving to 2.6.30 from 2.6.24-gentoo-r3 which hopefully won't break anything).

I'm not even sure where to start diagnosing this or what information may prove useful - can anyone offer any pointers or suggestions?

EDIT: Might have found it - I had some old PATA drivers also built into the kernel. Laptop seems a bit more responsive now, will check the desktop tomorrow and report back...
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Matt.

"Ninjas aren't dangerous. They're more afraid of you than you are of them." - The Tick.

szczerb · Posted: Sun Jun 21, 2009 9:14 pm Post subject:

I noticed the same thing when netbeans was being extracted on my T2370. I guess that choosing a different IO allocator or what it's called (there is deadline and two other - I'm not gonna run menuconfig right now to look for it, but I'm sure you know what I'm refering to) might change it.

mattsavigear · Posted: Sun Jun 21, 2009 9:15 pm Post subject:

Yeah, good plan. I'll fiddle with those if the driver removal I mentioned in my edit above doesn't sort things out.
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Matt.

"Ninjas aren't dangerous. They're more afraid of you than you are of them." - The Tick.

snIP3r · l33t Joined: 21 May 2004 Posts: 853 Location: germany

hi!

theres a thread in the forums "gentoo on amd64" section about the same problem you describe:

https://forums.gentoo.org/viewtopic-t-482731.html

perhaps this helps!

greets
snIP3r
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mattsavigear · Posted: Wed Jun 24, 2009 1:49 pm Post subject:

Thanks for the link. I think the stripping out of the extraneous Intel PATA drivers has helped quite a bit, but I'm still not 100% happy with the responsiveness.
_________________
Matt.

"Ninjas aren't dangerous. They're more afraid of you than you are of them." - The Tick.

energyman76b · Advocate Joined: 26 Mar 2003 Posts: 2048 Location: Germany

what io scheduler are you using? as? deadline cfq? Which kernel timer freuqency? 100? 300? 1000? Preemption? Voluntary or forced?

In my experience forced preemption is the worst when there are disk accesses and Voluntary the best. For the frequency - 300. And CFQ scheduler.
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mattsavigear · Posted: Thu Jun 25, 2009 5:56 am Post subject:

Currently using CFQ, 1000Hz and forced preemption - I sometimes use the machine for low-latency audio work. I think I'll build a couple of kernels and swap when I need to.

Oddly enough, by 32bit dedicated audio machine with these settings doesn't suffer from this problem.
_________________
Matt.

"Ninjas aren't dangerous. They're more afraid of you than you are of them." - The Tick.

energyman76b · Advocate Joined: 26 Mar 2003 Posts: 2048 Location: Germany

something you can play around with, without building different kernels is
/proc/sys/vm/dirty_writeback_centisecs
/proc/sys/vm/dirty_ratio
and other stuff in vm/
_________________
Study finds stunning lack of racial, gender, and economic diversity among middle-class white males

I identify as a dirty penismensch.