From: Hui Wang <john.wanghui@huawei.com>
To: <linux-kernel@vger.kernel.org>, <tglx@linutronix.de>
Cc: <guijianfeng@huawei.com>, <wencongyang2@huawei.com>,
<douliyang1@huawei.com>, <qiaonuohan@huawei.com>
Subject: [PATCH] x86/topology: use total_cpus for max logical packages calculation
Date: Wed, 7 Nov 2018 10:36:43 +0800 [thread overview]
Message-ID: <20181107023643.22174-1-john.wanghui@huawei.com> (raw)
nr_cpu_ids can be limited on the command line via nr_cpus=. This can break the
logical package management because it results in a smaller number of packages
while in kdump kernel.
Check below case:
There is a two sockets system, each socket has 8 cores, which has 16 logical
cpus while HT was turn on.
0 1 2 3 4 5 6 7 | 16 17 18 19 20 21 22 23
cores on socket 0 threads on socket 0
8 9 10 11 12 13 14 15 | 24 25 26 27 28 29 30 31
cores on socket 1 threads on socket 1
While start kdump kernel with option nr_cpus=16, and panic was triggered on one
of the cpus 24-31 eg. 26, then online cpu will be 1-15, 26(cpu 0 was disabled in
kdump), ncpus will be 16 and __max_logical_packages will be 1, but actually two
packages were booted on.
This issue can reproduced by set kdump option nr_cpus=<real physical core
numbers>, and then trigger panic on last socket's thread, for example:
taskset -c 26 echo c > /proc/sysrq-trigger
Use total_cpus which will not be limited by nr_cpus command line to calculate
the value of __max_logical_packages.
Signed-off-by: Hui Wang <john.wanghui@huawei.com>
---
arch/x86/kernel/smpboot.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index a9134d1910b9..ccd1f2a8e557 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1347,7 +1347,7 @@ void __init calculate_max_logical_packages(void)
* extrapolate the boot cpu's data to all packages.
*/
ncpus = cpu_data(0).booted_cores * topology_max_smt_threads();
- __max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus);
+ __max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
pr_info("Max logical packages: %u\n", __max_logical_packages);
}
--
2.17.0
next reply other threads:[~2018-11-07 2:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-07 2:36 Hui Wang [this message]
2018-12-18 12:42 ` [tip:x86/cpu] x86/topology: Use total_cpus for max logical packages calculation tip-bot for Hui Wang
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