On 07/20/16 23:56, Stephen Rothwell wrote:
> Hi all,
>
> Changes since 20160720:
>
on x86_64, when CONFIG_FB is not enabled:
ERROR: "remove_conflicting_framebuffers" [drivers/gpu/drm/virtio/virtio-gpu.ko]
undefined!
--
~Randy
___
Virtualization
An over-committed guest with more vCPUs than pCPUs has a heavy overload in
the two spin_on_owner. This blames on the lock holder preemption issue.
Kernel has an interface bool vcpu_is_preempted(int cpu) to see if a vCPU is
currently running or not. So break the spin loops on true condition.
An over-committed guest with more vCPUs than pCPUs has a heavy overhead in
osq_lock().
This is because vCPU A hold the osq lock and yield out, vCPU B wait per_cpu
node->locked to be set. IOW, vCPU B wait vCPU A to run and unlock the osq
lock.
Kernel has an interface bool vcpu_is_preempted(int
change from v2:
no code change, fix typos, update some comments
change from v1:
a simplier definition of default vcpu_is_preempted
skip mahcine type check on ppc, and add config. remove dedicated macro.
add one patch to drop overload of rwsem_spin_on_owner and
This is to fix some lock holder preemption issues. Some other locks
implementation do a spin loop before acquiring the lock itself.
Currently kernel has an interface of bool vcpu_is_preempted(int cpu). It
takes the cpu as parameter and return true if the cpu is preempted. Then
kernel can break the
This patch supports to fix lock holder preemption issue.
For kernel users, we could use bool vcpu_is_preempted(int cpu) to detech if
one vcpu is preempted or not.
The default implementation is a macro defined by false. So compiler can
wrap it out if arch dose not support such vcpu pteempted
