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Date: Mon, 18 Oct 2010 13:00:46 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
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To: "Alex,Shi" <alex.shi@intel.com>
cc: "Wu, Fengguang" <fengguang.wu@intel.com>,
        Pekka Enberg <penberg@kernel.org>,
        Pekka Enberg <penberg@cs.helsinki.fi>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        David Rientjes <rientjes@google.com>, Mel Gorman <mel@csn.ul.ie>,
        "npiggin@kernel.dk" <npiggin@kernel.dk>,
        "yanmin_zhang@linux.intel.com" <yanmin_zhang@linux.intel.com>,
        "Chen, Tim C" <tim.c.chen@intel.com>,
        "Li, Shaohua" <shaohua.li@intel.com>
Subject: Re: [UnifiedV4 00/16] The Unified slab allocator (V4)
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On Wed, 13 Oct 2010, Alex,Shi wrote:

> I got the code from
> git://git.kernel.org/pub/scm/linux/kernel/git/christoph/slab.git unified
> on branch "origin/unified" and do a patch base on 36-rc7 kernel. Then I
> tested the patch on our 2P/4P core2 machines and 2P NHM, 2P WSM
> machines. Most of benchmark have no clear improvement or regression. The
> testing benchmarks is listed here.
> http://kernel-perf.sourceforge.net/about_tests.php

Ah. Thanks. The tests needs to show a clear benefit for this to be a
viable solution. They did earlier without all the NUMA queuing on SMP.

> BTW, I save several time kernel panic in fio testing:
> ===================
> > Pid: 776, comm: kswapd0 Not tainted 2.6.36-rc7-unified #1 X8DTN/X8DTN
> > > RIP: 0010:[<ffffffff810cc21c>]  [<ffffffff810cc21c>] slab_alloc
> > > +0x562/0x6f2

Cannot see the error message? I guess this is the result of a BUG_ON()?
I'll try to run that fio test first.

> kswapd0: page allocation failure. order:0, mode:0xd0
> Pid: 714, comm: kswapd0 Not tainted 2.6.36-rc7-unified #1
> Call Trace:
> [<ffffffff8109fcf4>] ? __alloc_pages_nodemask+0x63f/0x6c7
> [<ffffffff8100328e>] ? apic_timer_interrupt+0xe/0x20
> [<ffffffff810cc6f7>] ? new_slab+0xac/0x277
> [<ffffffff810cce1e>] ? slab_alloc+0x55c/0x6e8
> [<ffffffff810ce58b>] ? shared_caches+0x31/0xd9
> [<ffffffff810ce110>] ? __kmalloc+0xb0/0xff
> [<ffffffff810ce58b>] ? shared_caches+0x31/0xd9
> [<ffffffff810ce649>] ? expire_alien_caches+0x16/0x8d
> [<ffffffff810cde25>] ? kmem_cache_expire_all+0xf6/0x14d

Expiration needs to get the gfp flags from the reclaim context. And we
now have more allocations in a reclaim context.

> slab_unreclaimable:2963060kB kernel_stack:1016kB pagetables:656kB

3GB unreclaimable.... Memory leak.