[PATCH] locking/paravirt: Fix performance regression on core bonded vCPU

Juergen Gross
Thu, 03 Nov 2022 14:09:08 -0000

On 03.11.22 14:58, johnnyaiai wrote:
> Thanks for reply! I think nopvspin parameters controls
> pvspinlock or native spinlock. a vm guest always running
> on virtspin wheather nopvspin sets or not when EXITS_HALT
> not supported by hypervisor. So provide a missing parameter
> 'novirtspin'.

Your patch is doing:

     static_branch_disable(&virt_spin_lock_key);

in case your parameter has been specified.

When running as Xen guest the related coding is doing:

     static_branch_disable(&virt_spin_lock_key);

Only when running as KVM guest there is a difference, but this could be changed
by modifying kvm_spinlock_init().

Having two parameters with the same or very similar semantics is not a good
idea IMO.


Juergen
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_0xB0DE9DD628BF132F.asc
Type: application/pgp-keys
Size: 3098 bytes
Desc: OpenPGP public key
URL:
<http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20221103/56806df8/attachment.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_signature
Type: application/pgp-signature
Size: 495 bytes
Desc: OpenPGP digital signature
URL:
<http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20221103/56806df8/attachment.sig>