vm problems

vm problems

[Gergely Madarasz]

Hello,

I get hundreds of this error message:

__alloc_pages: 0-order allocation failed.

The machine is an IBM x250 with 4G ram, the kernel is vanilla 2.4.9 and
2.4.9-ac3, no swap, running bonnie++. When the memory fills up with cache,
I start receiving the error message. 

             total       used       free     shared    buffers     cached
Mem:       3863628    3854532       9096          0       5160    3734832
-/+ buffers/cache:     114540    3749088
Swap:            0          0          0

-- 
Madarasz Gergely   gorgo@thunderchild.debian.net   gorgo@linux.rulez.org
    It's practically impossible to look at a penguin and feel angry.
        Egy pingvinre gyakorlatilag lehetetlen haragosan nezni.
                  HuLUG: http://mlf.linux.rulez.org/

Re: vm problems

[Gergely Madarasz]

On Wed, Aug 29, 2001 at 01:14:19PM +0200, Gergely Madarasz wrote:
> Hello,
> 
> I get hundreds of this error message:
> 
> __alloc_pages: 0-order allocation failed.
> 
> The machine is an IBM x250 with 4G ram, the kernel is vanilla 2.4.9 and
> 2.4.9-ac3, no swap, running bonnie++. When the memory fills up with cache,
> I start receiving the error message. 

actually I thought I was running 2.4.9-ac3, but no, and I see the message
is commented out in 2.4.9-ac3. Does this mean that it doesn't mean
anything serious? Some of my processes were stuck in uninterruptible
sleep, I couldn't even shutdown correctly, so there are some problems.

-- 
Madarasz Gergely   gorgo@thunderchild.debian.net   gorgo@linux.rulez.org
    It's practically impossible to look at a penguin and feel angry.
        Egy pingvinre gyakorlatilag lehetetlen haragosan nezni.
                  HuLUG: http://mlf.linux.rulez.org/

Re: vm problems

[Daniel Phillips]

On August 29, 2001 01:47 pm, Gergely Madarasz wrote:
> On Wed, Aug 29, 2001 at 01:14:19PM +0200, Gergely Madarasz wrote:
> > Hello,
> > 
> > I get hundreds of this error message:
> > 
> > __alloc_pages: 0-order allocation failed.
> > 
> > The machine is an IBM x250 with 4G ram, the kernel is vanilla 2.4.9 and
> > 2.4.9-ac3, no swap, running bonnie++. When the memory fills up with cache,
> > I start receiving the error message. 
> 
> actually I thought I was running 2.4.9-ac3, but no, and I see the message
> is commented out in 2.4.9-ac3. Does this mean that it doesn't mean
> anything serious? Some of my processes were stuck in uninterruptible
> sleep, I couldn't even shutdown correctly, so there are some problems.

Please try it again with this patch so we can see what kind of allocation is failing:

--- 2.4.9.clean/mm/page_alloc.c	Thu Aug 16 12:43:02 2001
+++ 2.4.9/mm/page_alloc.c	Mon Aug 20 22:05:40 2001
@@ -502,7 +502,8 @@
 	}
 
 	/* No luck.. */
-	printk(KERN_ERR "__alloc_pages: %lu-order allocation failed.\n", order);
+	printk(KERN_ERR "__alloc_pages: %lu-order allocation failed (gfp=0x%x/%i).\n",
+		order, gfp_mask, !!(current->flags & PF_MEMALLOC));
 	return NULL;
 }
 

Re: vm problems

[Stephan von Krawczynski]

On Wed, 29 Aug 2001 13:14:19 +0200
Gergely Madarasz <gorgo@thunderchild.debian.net> wrote:

> Hello,
> 
> I get hundreds of this error message:
> 
> __alloc_pages: 0-order allocation failed.
> 
> The machine is an IBM x250 with 4G ram, the kernel is vanilla 2.4.9 and
> 2.4.9-ac3, no swap, running bonnie++. When the memory fills up with cache,
> I start receiving the error message. 
> 
>              total       used       free     shared    buffers     cached
> Mem:       3863628    3854532       9096          0       5160    3734832
> -/+ buffers/cache:     114540    3749088
> Swap:            0          0          0

Unfortunately I found out this is "normal" behaviour, not only under 2.4.9 but also 2.4.8 and 2.4.7. You could use just about any test that does filesystem load with more data moved than you have physical mem. It basically means that you can easily break the vm management by forcing it in a state where "cleanup" has to be done to find free pages (e.g. page_launder). If you have enough spare time you can try to make page_launder run not only through 1/64 of the list but all through and find out in the end, that it cannot find free pages not matter how often it is run. This looks like a self-produced deadlock situation. On the one hand the basic strategy seems to use as much resources (mem) as possible to gain speed, on the other hand there is no way out, if resources get very low, and this basic strategy fails (which you can see because performance drops down below the cellar).
Try 2.4.10-pre2, possibly you find out, that it doesn't fail that often, but performance stays low.

Regards, Stephan