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From: Uladzislau Rezki <urezki@gmail.com>
To: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	GregKroah-Hartmangregkh@linuxfoundation.org,
	peterz@infradead.org
Subject: nr_cpu_ids vs AMD 3970x(32 physical CPUs)
Date: Fri, 3 Jul 2020 17:57:49 +0200	[thread overview]
Message-ID: <20200703155749.GA6255@pc636> (raw)

Hello, folk.

I have a system based on AMD 3970x CPUs. It has 32 physical cores
and 64 threads. It seems that "nr_cpu_ids" variable is not correctly
set on latest 5.8-rc3 kernel. Please have a look below on dmesg output:

<snip>
urezki@pc638:~$ sudo dmesg | grep 128
[    0.000000] IOAPIC[0]: apic_id 128, version 33, address 0xfec00000, GSI 0-23
[    0.000000] smpboot: Allowing 128 CPUs, 64 hotplug CPUs
[    0.000000] setup_percpu: NR_CPUS:512 nr_cpumask_bits:512 nr_cpu_ids:128 nr_node_ids:1
...
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=128, Nodes=1
[    0.000000] rcu:     RCU restricting CPUs from NR_CPUS=512 to nr_cpu_ids=128.
[    0.000000] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=128
urezki@pc638:~$
<snip>

For example SLUB thinks that it deals with 128 CPUs in the system what is
wrong if i do not miss something. Since nr_cpu_ids is broken(?), thus the
"cpu_possible_mask" does not correspond to reality as well.

Any thoughts?

Thanks!

--
Vlad Rezki

             reply	other threads:[~2020-07-03 15:57 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-03 15:57 Uladzislau Rezki [this message]
2020-07-03 16:56 ` nr_cpu_ids vs AMD 3970x(32 physical CPUs) Peter Zijlstra
2020-07-03 17:09   ` Uladzislau Rezki
2020-07-03 17:38     ` Peter Zijlstra
2020-07-03 19:26       ` Uladzislau Rezki
2020-07-03 17:07 ` Gabriel C
2020-07-03 17:24   ` Uladzislau Rezki
2020-07-03 17:45   ` Peter Zijlstra
2020-07-03 18:36     ` Gabriel C
2020-07-03 19:05 ` peter enderborg
2020-07-03 19:28   ` Uladzislau Rezki
2020-07-03 20:08     ` Linus Torvalds
2020-07-03 21:20       ` Uladzislau Rezki
2020-07-03 21:51         ` Matthew Wilcox
2020-07-03 22:22           ` Uladzislau Rezki

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