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SubjectRe: [PATCH v11 4/5] locking/qspinlock: Introduce starvation avoidance into CNA
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> On Sep 15, 2020, at 3:24 PM, Randy Dunlap <rdunlap@infradead.org> wrote:
>
> Hi,
>
> Entries in the kernel-parameters.txt file should be kept in alphabetical order
> mostly (there are a few exceptions where related options are kept together).
>
>
>
> On 9/15/20 11:05 AM, Alex Kogan wrote:
>> Keep track of the time the thread at the head of the secondary queue
>> has been waiting, and force inter-node handoff once this time passes
>> a preset threshold. The default value for the threshold (10ms) can be
>> overridden with the new kernel boot command-line option
>> "numa_spinlock_threshold". The ms value is translated internally to the
>> nearest rounded-up jiffies.
>>
>> Signed-off-by: Alex Kogan <alex.kogan@oracle.com>
>> Reviewed-by: Steve Sistare <steven.sistare@oracle.com>
>> Reviewed-by: Waiman Long <longman@redhat.com>
>> ---
>> .../admin-guide/kernel-parameters.txt | 9 ++
>> kernel/locking/qspinlock_cna.h | 95 ++++++++++++++++---
>> 2 files changed, 92 insertions(+), 12 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index 51ce050f8701..73ab23a47b97 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -3363,6 +3363,15 @@
>> Not specifying this option is equivalent to
>> numa_spinlock=auto.
>>
>> + numa_spinlock_threshold= [NUMA, PV_OPS]
>> + Set the time threshold in milliseconds for the
>> + number of intra-node lock hand-offs before the
>> + NUMA-aware spinlock is forced to be passed to
>> + a thread on another NUMA node. Valid values
>> + are in the [1..100] range. Smaller values result
>> + in a more fair, but less performant spinlock,
>> + and vice versa. The default value is 10.
>> +
>> cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
>> CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
>> Some features depend on CPU0. Known dependencies are:
>
>
> This new entry and numa_spinlock from patch 3/5 should go between these other 2 NUMA entries:
>
> numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
> Allowed values are enable and disable
>
> numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
> 'node', 'default' can be specified
> This can be set from sysctl after boot.
> See Documentation/admin-guide/sysctl/vm.rst for details.
Will fix that, thanks.

>
>
> Oooh, that cpu0_hotplug entry is way out of place. I'll send a patch for that.
Sounds good.

— Alex
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