linux-kernel - 32/64-bit NUMA consolidation behavior regresion

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <50B6A66E.8030406@linux.vnet.ibm.com>
Date:	Wed, 28 Nov 2012 16:03:58 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: 32/64-bit NUMA consolidation behavior regresion

Hi Tejun,

I was bisecting a boot problem on a 32-bit NUMA kernel and it bisected
down to commit 8db78cc4.  It turns out that, with this patch,
pcpu_need_numa() changed its return value on my system from 1 to 0.
What that basically meant was that we stopped using the remapped lowmem
areas for percpu data.

My system is just qemu booted with:

-smp 8 -m 8192 -numa node,nodeid=0,cpus=0-3 -numa node,nodeid=1,cpus=4-7

Watch the "PERCPU:" line early in boot, and you can see the "Embedded"
come and go with or without your patch:

[    0.000000] PERCPU: Embedded 11 pages/cpu @f3000000 s30592 r0 d14464
vs
[    0.000000] PERCPU: 11 4K pages/cpu @f83fe000 s30592 r0 d14464

I believe this has to do with the hunks in your patch that do:

-#ifdef CONFIG_X86_64
        init_cpu_to_node();
-#endif
...
-#ifdef CONFIG_X86_32
-DEFINE_EARLY_PER_CPU(int, x86_cpu_to_node_map, 0);
-#else
 DEFINE_EARLY_PER_CPU(int, x86_cpu_to_node_map, NUMA_NO_NODE);
-#endif
 EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_node_map);

I don't have a fix handy because I'm working on the original problem,
but I just happened to run across this during a bisect.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/