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#1 2012-10-05 09:47:22

darkraven
Member
Registered: 2009-06-08
Posts: 29

[SOLVED] bfq io scheduler causes hangs.

Today I compiled my kernel from zen-kernel source and set the default io scheduler to be BFQ.

After I logged into my account, the system hangs after a couple of seconds. The system is still responsive, already started programs works well. Attempts to start new program will hang indefinitely (I waited for about 1~2 min).

I reboot my computer and the problem persists, though the system hangs on different time point.

During the second hang, I issued 'echo noop > /sys/block/sda/queue/scheduler'. Almost immediately, my system back to normal. So I think it's BFQ's fault.

I'm currently using zfsonlinux, which could leads to the thought that maybe bfq doesn't play well with zfs, but this is not my first experience with bfq. I have tried bfq when I was using xfs/ext4 (about 1 yr ago), it's the same problem which drove my away from bfq.

Last edited by darkraven (2012-10-16 12:43:08)

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#2 2012-10-05 11:10:27

kokoko3k
Member
Registered: 2008-11-14
Posts: 1,438

Re: [SOLVED] bfq io scheduler causes hangs.

Yeah, i've had the same with vmware

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#3 2012-10-05 13:06:16

martadinata
Member
Registered: 2012-01-26
Posts: 25

Re: [SOLVED] bfq io scheduler causes hangs.

i don't use zfsonlinux, but i can inform you that im using xfs ext4 reiserfs also btrfs , without any problem with bfq scheduler. im using linux-pf kernel, linux-ck also and work flawlessly...

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#4 2012-10-05 14:00:52

darkraven
Member
Registered: 2009-06-08
Posts: 29

Re: [SOLVED] bfq io scheduler causes hangs.

martadinata wrote:

i don't use zfsonlinux, but i can inform you that im using xfs ext4 reiserfs also btrfs , without any problem with bfq scheduler. im using linux-pf kernel, linux-ck also and work flawlessly...

I sure believe there are people who are using bfq without any problem, but I'm also not lying about my problem.

There was a time when bfq works flawlessly on my system (I don't know the exact time, maybe 1.5~2 yr ago, and at that time I'm using either xfs or ext4. I have only used zfslinux for a couple of days), then this problem sneaks in (I'm not quite sure if they are really the same problem, but the behavior I saw is identical) . At that time I'm not confident enough to report this problem (I'm not very confident now either, maybe it's just my configuration is wrong), so I simply stop using bfq, and switch back to cfq.

Several days ago I heard of bfq again on the zfsonlinux mailing list, when someone states that it's better using bfq rather cfq with zfsonlinux. I thought maybe time has cured this problem, so I give it another try, only got disappointed with the results sad

Last edited by darkraven (2012-10-05 14:01:59)

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#5 2012-10-05 14:57:53

brebs
Member
Registered: 2007-04-03
Posts: 3,406

Re: [SOLVED] bfq io scheduler causes hangs.

Try pf-kernel instead. With it, I've never had any problems with BFQ.

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#6 2012-10-05 16:55:01

WonderWoofy
Member
From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: [SOLVED] bfq io scheduler causes hangs.

darkraven wrote:

I sure believe there are people who are using bfq without any problem, but I'm also not lying about my problem.

I really don't think the intent was to call you a liar.  I think it was simply to inform you that it was not a problem inherent with just bfq. 

Anyway, you said you cimpiled the kernel yourself.  Have you tried the linux-ck package from graysky's repo?

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#7 2012-10-06 13:43:06

darkraven
Member
Registered: 2009-06-08
Posts: 29

Re: [SOLVED] bfq io scheduler causes hangs.

brebs wrote:

Try pf-kernel instead. With it, I've never had any problems with BFQ.

Thanks, pk-kernel works well for me so far.

Maybe I should report this to zen-kernel.

EDIT:I want to withdraw what I have said. BFQ successfully hung my system with pf-linux.
This doesn't always happend, but with this hang rate, I'll consider bfq as unusable.

Last edited by darkraven (2012-10-06 14:39:00)

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#8 2012-10-16 12:41:32

darkraven
Member
Registered: 2009-06-08
Posts: 29

Re: [SOLVED] bfq io scheduler causes hangs.

Sorry for bumping this thread.

For anyone who has the same problem or is interested in this, there is a patch which seems to fix this.

https://groups.google.com/group/bfq-ios … authuser=0

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