Re: 2.5.33-mm3 dbench hang and 2.5.33 page allocation failures

[Andrew Morton <akpm@zip.com.au>]

Steven Cole wrote:
> 
> I booted 2.5.33-mm3 and ran dbench with increasing
> numbers of clients: 1,2,3,4,6,8,10,12,16,etc. while
> running vmstat -n 1 600 from another terminal.
> 
> After about 3 minutes, the output from vmstat stopped,
> and the dbench 16 output stopped.  The machine would
> respond to pings, but not to anything else. I had to
> hard-reset the box. Nothing interesting was saved in
> /var/log/messages. I have the output from vmstat if needed.

That sounds like a race-leading-to-deadlock.  Feeding the SYSRQ-T
output into ksymoops is about the only way you have of diagnosing that
I'm afraid.

> The test box is dual p3, 1GB, scsi, ext3 fs.
> Kernels are SMP,_HIGHMEM4G, no PREEMPT, no HIGHPTE.
> 
> Earlier this morning, I ran 2.5.33 and the dbench test and got many
> page allocation failure messages before I terminated the test.
> 
> Steven
> 
> Sep  5 07:20:01 spc5 kernel: dbench: page allocation failure. order:0, mode:0x50
> Sep  5 07:28:32 spc5 kernel: dbench: page allocation failure. order:0, mode:0x50

Presumably, this was when running a lot more than 16 clients?

It's just a warning, btw.  Allocation failures are expected for GFP_NOIO
allocations.  Increasingly so lately, actually.
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