Re: [RFC][PATCH 0/6] fix topology for multi-NUMA-node CPUs

[Aravind Gopalakrishnan]

On 9/22/2014 9:33 AM, Aravind Gopalakrishnan wrote:
> This is a big fat RFC.  It takes quite a few liberties with the
> multi-core topology level that I'm not completely comfortable
> with.
>
> It has only been tested lightly.
>
> Full dmesg for a Cluster-on-Die system with this set applied,
> and sched_debug on the command-line is here:
>
> http://sr71.net/~dave/intel/full-dmesg-hswep-20140917.txt 
> <http://sr71.net/%7Edave/intel/full-dmesg-hswep-20140917.txt>
>
> ---
>
> I'm getting the spew below when booting with Haswell (Xeon
> E5-2699 v3) CPUs and the "Cluster-on-Die" (CoD) feature enabled
> in the BIOS.  It seems similar to the issue that some folks from
> AMD ran in to on their systems and addressed in this commit:
>
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=161270fc1f9ddfc17154e0d49291472a9cdef7db
>
> Both these Intel and AMD systems break an assumption which is
> being enforced by topology_sane(): a socket may not contain more
> than one NUMA node.
>
> AMD special-cased their system by looking for a cpuid flag. The
> Intel mode is dependent on BIOS options and I do not know of a
> way which it is enumerated other than the tables being parsed
> during the CPU bringup process.
>
> This also fixes sysfs because CPUs with the same 'physical_package_id'
> in /sys/devices/system/cpu/cpu*/topology/ are not listed together
> in the same 'core_siblings_list'.  This violates a statement from
> Documentation/ABI/testing/sysfs-devices-system-cpu:
>
>         core_siblings: internal kernel map of cpu#'s hardware threads
>         within the same physical_package_id.
>
>         core_siblings_list: human-readable list of the logical CPU
>         numbers within the same physical_package_id as cpu#.
>
> The sysfs effects here cause an issue with the hwloc tool where
> it gets confused and thinks there are more sockets than are
> physically present.
>
> Before this set, there are two packages:
>
> # cd /sys/devices/system/cpu/
> # cat cpu*/topology/physical_package_id | sort | uniq -c
>      18 0
>      18 1
>
> But 4 _sets_ of core siblings:
>
> # cat cpu*/topology/core_siblings_list | sort | uniq -c
>       9 0-8
>       9 18-26
>       9 27-35
>       9 9-17
>
> After this set, there are only 2 sets of core siblings, which
> is what we expect for a 2-socket system.
>
> # cat cpu*/topology/physical_package_id | sort | uniq -c
>      18 0
>      18 1
> # cat cpu*/topology/core_siblings_list | sort | uniq -c
>      18 0-17
>      18 18-35
>
>
> Example spew:
> ...
>         NMI watchdog: enabled on all CPUs, permanently consumes one 
> hw-PMU counter.
>          #2  #3  #4  #5  #6  #7  #8
>         .... node  #1, CPUs:    #9
>         ------------[ cut here ]------------
>         WARNING: CPU: 9 PID: 0 at 
> /home/ak/hle/linux-hle-2.6/arch/x86/kernel/smpboot.c:306 
> topology_sane.isra.2+0x74/0x90()
>         sched: CPU #9's mc-sibling CPU #0 is not on the same node! 
> [node: 1 != 0]. Ignoring dependency.
>         Modules linked in:
>         CPU: 9 PID: 0 Comm: swapper/9 Not tainted 
> 3.17.0-rc1-00293-g8e01c4d-dirty #631
>         Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS 
> GRNDSDP1.86B.0036.R05.1407140519 07/14/2014
>         0000000000000009 ffff88046ddabe00 ffffffff8172e485 
> ffff88046ddabe48
>         ffff88046ddabe38 ffffffff8109691d 000000000000b001 
> 0000000000000009
>         ffff88086fc12580 000000000000b020 0000000000000009 
> ffff88046ddabe98
>         Call Trace:
>         [<ffffffff8172e485>] dump_stack+0x45/0x56
>         [<ffffffff8109691d>] warn_slowpath_common+0x7d/0xa0
>         [<ffffffff8109698c>] warn_slowpath_fmt+0x4c/0x50
>         [<ffffffff81074f94>] topology_sane.isra.2+0x74/0x90
>         [<ffffffff8107530e>] set_cpu_sibling_map+0x31e/0x4f0
>         [<ffffffff8107568d>] start_secondary+0x1ad/0x240
>         ---[ end trace 3fe5f587a9fcde61 ]---
>         #10 #11 #12 #13 #14 #15 #16 #17
>         .... node  #2, CPUs:   #18 #19 #20 #21 #22 #23 #24 #25 #26
>         .... node  #3, CPUs:   #27 #28 #29 #30 #31 #32 #33 #34 #35


Hi,
I looked at the topology info from sysfs both w/ and w/o the patch 
series and they are identical.
So, the patches seem to work fine on an AMD MCM part.

Tested-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>

Thanks,
-Aravind.
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