linux-ext4 - Re: Overwriting w/ discard-capable drive causes soft-lockup in ext4 journal code, 2.6.28.8

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Message-ID: <f3177b9e0903171219l2cd6ef84g5416275e999132be@mail.gmail.com>
Date:	Tue, 17 Mar 2009 13:19:33 -0600
From:	Chris Worley <worleys@...il.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Overwriting w/ discard-capable drive causes soft-lockup in ext4 
	journal code, 2.6.28.8

On Tue, Mar 17, 2009 at 12:01 PM, Eric Sandeen <sandeen@...hat.com> wrote:
> Chris Worley wrote:
>> The issue I'm seeing is caused by running this repeatedly on an ext4
>> fs (2.6.28.8 kernel) w/ discards enabled (a ram-based MTD device
>> contains the fs):
>>
>> while `true`
>> do  i=0
>>      while [ $i -lt 100 ]
>>      do dd of=foo"$i" if=/dev/zero bs=1024k oflag=direct &
>>           let i=$i+1
>>      done
>>      wait
>> done
>>
>> (Note: the loop is intended to fill-up the fs w/ 100 dd threads...
>> successive re-runs of the loop will rewrite the same files from
>> scratch.)
>>
>> ... It causes "soft-lockup" issues on successive iterations,
>> immediately as the DD's are launched, as previous foo files get their
>> blocks discarded.
>
> I need to find a machine w/ more memory to test on :)  but with a device
> of half that size, on 2.6.29-rc7 machine w/ 2 cpus and 2G ram, I'm not
> seeing it...
>
> Any chance you can try a 2.6.29-rcX kernel just to double-check?

I'm not able to repeat w/ 2.6.29-rc8.

The system just limps-along, though; SATA doesn't work, Ethernet
doesn't work, and system response is slow... but disk speed is as
expected, and no soft-lockup issues.

Chris
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