linux-kernel - Re: OOM-killer and strange RSS value in 3.9-rc7

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Date:	Fri, 26 Apr 2013 14:42:32 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Han Pingtian <hanpt@...ux.vnet.ibm.com>
cc:	LKML <linux-kernel@...r.kernel.org>, mhocko@...e.cz,
	penberg@...nel.org, rientjes@...gle.com, linux-mm@...ck.org
Subject: Re: OOM-killer and strange RSS value in 3.9-rc7

On Fri, 26 Apr 2013, Han Pingtian wrote:

> Could you give me some hints about how to verify them? Only I can do is
> adding two printk() statements to print the vaules in those two
> functions:

Ok thats good. nr->partial needs to be bigger than min_partial in order
for frees to occur. So they do occur.

> And looks like only printk() in __slab_free() is invoked. I got about 6764
> lines of something like this:
>
> --------------------------------------------------------------------------------
> Apr 26 01:04:05 riblp3 kernel: [    6.969775] In __slab_free(); kmalloc-8192: n->nr_partial=2, s->min_partial=6
> Apr 26 01:04:05 riblp3 kernel: [    6.970154] In __slab_free(); kmalloc-8192: n->nr_partial=3, s->min_partial=6
> Apr 26 01:04:05 riblp3 kernel: [    6.979489] In __slab_free(); kmalloc-8192: n->nr_partial=4, s->min_partial=6
> Apr 26 01:04:05 riblp3 kernel: [    6.979823] In __slab_free(); kmalloc-8192: n->nr_partial=5, s->min_partial=6
> Apr 26 01:04:05 riblp3 kernel: [    9.500383] In __slab_free(); kmalloc-8192: n->nr_partial=7, s->min_partial=6
> Apr 26 01:04:05 riblp3 kernel: [    9.509736] In __slab_free(); kmalloc-8192: n->nr_partial=7, s->min_partial=6
> Apr 26 01:04:08 riblp3 kernel: [   42.314395] In __slab_free(); kmalloc-8192: n->nr_partial=100, s->min_partial=6
> Apr 26 01:04:08 riblp3 kernel: [   42.410333] In __slab_free(); kmalloc-8192: n->nr_partial=100, s->min_partial=6
> Apr 26 01:04:09 riblp3 kernel: [   43.411851] In __slab_free(); kmalloc-8192: n->nr_partial=339, s->min_partial=6
> Apr 26 01:04:09 riblp3 kernel: [   43.411980] In __slab_free(); kmalloc-8192: n->nr_partial=338, s->min_partial=6
> Apr 26 01:04:09 riblp3 kernel: [   43.412083] In __slab_free(); kmalloc-8192: n->nr_partial=337, s->min_partial=6
> --------------------------------------------------------------------------------
> The s->min_partial is always "6" and most of n->nr_partial is bigger than
> its partner of the same line.

Thats the way it should be. But the mystery is still there. Why do the
pages not get freed? Can you add a printk in __free_slab to verify that it
actually gets called? Print s->name to see which slab is affected by the
free.

Is there any way I can run a powerpc kernel that shows the issue on x86
with an emulator?

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