linux-kernel - Re: [Problem] System hang when I run pounder and syscall test on kernel 2.6.18-rc5

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Date:	Mon, 11 Sep 2006 10:09:56 +0800
From:	Shu Qing Yang <yangshuq@...ibm.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [Problem] System hang when I run pounder and syscall test on kernel
 2.6.18-rc5

Andrew Morton <akpm@...l.org> wrote on 2006-09-09 00:52:41:

> On Fri, 8 Sep 2006 19:36:40 +0800
> Shu Qing Yang <yangshuq@...ibm.com> wrote:
> 
> > Andrew Morton <akpm@...l.org> wrote on 2006-09-08 10:14:34:
> > 
> > > On Thu, 7 Sep 2006 12:35:09 +0800
> > > Shu Qing Yang <yangshuq@...ibm.com> wrote:
> > > 
> > > > Problem description:
> > > >     I run pounder, scsi_debug on a machine. Then start 200 random 
> > syscall 
> > > > test 
> > > > simultaneously. Tens of minutes later, the system hang.
> > > 
> > > What is "pounder" and from where can it be obtained?
> > > 
> > Thanks for your reply.
> > 
> > Pounder is part of ltp and locate in LTPROOT/testcases/pounder21. 
> > It is a suit of test cases including mem_alloc, random_syscall, 
bonnie++, 
> > etc.
> 
> OK, thanks.
> 
> > > Running two tests at the same time complicates things.  The next 
step
> > > should be to determine whether it is reproducible.  If it is, then 
see 
> > if
> > > it is reproducible with just one test running (presumably pounder?)
> > > 
> > Running multiple cases simultaneously is to stress kernel more. And 
> > because of
> > lack of machine resource I have no chance to reproduce it.
> > 
> > > It would be helpful to provide sufficient information to give others 
a
> > > chance of reproducing it: amount of memory, method for configuring 
the
> > > scsi-debug "disks", method for invoking pounder, etc.
> > > 
> > The machine belongs to IBM p-Series with power5+ cpu and 2GB memory.
> > Run LTPROOT/testscript/ltp-scsi_debug.sh and 
> > LTPROOT/testscript/pounder21/pounder directly.
> > No extra parameters.   The command to load scsi_debug module is: 
> > modprobe scsi_debug max_luns=2 num_tgts=2 add_host=2 dev_size_mb=20
> > 
> > ...
> >
> > I can not excute sysrq command now. But I can get memory allocation 
> > information from xmon, 
> > which indicates your guess may be right.
> > 
> > 1:mon> mi
> > Mem-info:
> > DMA per-cpu:
> > cpu 0 hot: high 6, batch 1 used:5
> > cpu 0 cold: high 2, batch 1 used:1
> > cpu 1 hot: high 6, batch 1 used:5
> > cpu 1 cold: high 2, batch 1 used:1
> > cpu 2 hot: high 6, batch 1 used:5
> > cpu 2 cold: high 2, batch 1 used:1
> > cpu 3 hot: high 6, batch 1 used:3
> > cpu 3 cold: high 2, batch 1 used:1
> > cpu 4 hot: high 6, batch 1 used:5
> > cpu 4 cold: high 2, batch 1 used:1
> > cpu 5 hot: high 6, batch 1 used:4
> > cpu 5 cold: high 2, batch 1 used:0
> > DMA32 per-cpu: empty
> > Normal per-cpu: empty
> > HighMem per-cpu: empty
> > Free pages:        6976kB (0kB HighMem)
> > Active:6141 inactive:11012 dirty:4742 writeback:0 unstable:0 free:109 
> > slab:11925 mapped:7 pagetables:7061
> > DMA free:6976kB min:5760kB low:7168kB high:8640kB active:393024kB 
> > inactive:704768kB present:2097152kB pages_scanned:5172 
all_unreclaimable? 
> > no
> > lowmem_reserve[]: 0 0 0 0
> > DMA32 free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB 
> > present:0kB pages_scanned:0 all_unreclaimable? no
> > lowmem_reserve[]: 0 0 0 0
> > Normal free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB 
> > present:0kB pages_scanned:0 all_unreclaimable? no
> > lowmem_reserve[]: 0 0 0 0
> > HighMem free:0kB min:2048kB low:2048kB high:2048kB active:0kB 
inactive:0kB 
> > present:0kB pages_scanned:0 all_unreclaimable? no
> > lowmem_reserve[]: 0 0 0 0
> > DMA: 19*64kB 1*128kB 2*256kB 0*512kB 1*1024kB 0*2048kB 1*4096kB 
0*8192kB 
> > 0*16384kB = 6976kB
> > DMA32: empty
> > Normal: empty
> > HighMem: empty
> > Swap cache: add 439156, delete 439156, find 50391/101032, race 26+79
> > Free swap  = 0kB
> > Total swap = 855552kB
> > Free swap:            0kB
> > 32768 pages of RAM
> > 408 reserved pages
> > 6834 pages shared
> > 0 pages swap cached
> 
> So we ran out of memory and we ran out of swap.
> 
> Possibly what has happened here is that the machine is doing a huge 
amount
> of work scanning pages and pretty soon it will enter the oom-killer to 
kill
> some userspace process.  But before that happened, the softlockup 
detector
> triggered.
> 
> But the machine _should_ have recovered.  If it hung for more than a few
> seconds then that's bad behaviour.  If it hung for more than a few 
minutes
> then that should be considered a bug.  If it hung for ever then that's
> definitely a bug.
> 
> Do you recall approximately how long the machine spent in this state?
System stayed in hang ten minutes at least. Then I forced it into xmon via 
sysrq.
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