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Re: BUG() in end_page_writeback(), stack overflows and system speed decr

To: Juergen Urban <JuergenUrban@xxxxxx>
Subject: Re: BUG() in end_page_writeback(), stack overflows and system speed decrease with XFS over USB
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Fri, 20 Nov 2009 11:08:12 -0600
Cc: xfs@xxxxxxxxxxx
In-reply-to: <4B06C58F.5070203@xxxxxxxxxxx>
References: <200911190957.45957.JuergenUrban@xxxxxx> <4B0587B0.3020702@xxxxxxxxxxx> <200911201723.48033.JuergenUrban@xxxxxx> <4B06C58F.5070203@xxxxxxxxxxx>
User-agent: Thunderbird 2.0.0.23 (Macintosh/20090812)
Eric Sandeen wrote:
> Juergen Urban wrote:
>> On Thursday 19 November 2009 19:00:16 Eric Sandeen wrote:
>>> Juergen Urban wrote:
>>>> Hello,
>>>>
>>>> my machine is running very unstable since I use XFS on an external USB
>>>> harddisc (855 GByte XFS partition on 1TByte). One problem was the stack
>>>> overflows caused by the large stack use of XFS, USB, SCSI and VFS in
>>>> Linux 2.6.23.13. NFS on XFS caused much more stack overflows. I think I
>>>> got around the stack overflows by disabling preemption, SMP and NFS in
>>>> Linux, but I am not sure about it. I think that I didn't got a message
>>>> from the stack overflow detection after this.
>>> Are you on 4k stacks?  To be honest I'd still expect things to be mostly
>>> ok stack-wise even if so.
>> No, I am using 8k stacks.
> 
> Hmm.
> 

BTW if you are still seeing stack overflows when testing w/ the newer
kernel, we can use some tracing to see what the stack backtrace is:

sysctl -w kernel.stack_tracer_enabled=1
mount -t debugfs none /sys/kernel/debug/

and then look in:

/sys/kernel/debug/tracing/stack_trace
/sys/kernel/debug/tracing/stack_max_size

-Eric

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