mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
90 lines
2.7 KiB
90 lines
2.7 KiB
.. SPDX-License-Identifier: GPL-2.0 |
|
|
|
.. _perf_index: |
|
|
|
===================== |
|
Perf Event Attributes |
|
===================== |
|
|
|
:Author: Andrew Murray <[email protected]> |
|
:Date: 2019-03-06 |
|
|
|
exclude_user |
|
------------ |
|
|
|
This attribute excludes userspace. |
|
|
|
Userspace always runs at EL0 and thus this attribute will exclude EL0. |
|
|
|
|
|
exclude_kernel |
|
-------------- |
|
|
|
This attribute excludes the kernel. |
|
|
|
The kernel runs at EL2 with VHE and EL1 without. Guest kernels always run |
|
at EL1. |
|
|
|
For the host this attribute will exclude EL1 and additionally EL2 on a VHE |
|
system. |
|
|
|
For the guest this attribute will exclude EL1. Please note that EL2 is |
|
never counted within a guest. |
|
|
|
|
|
exclude_hv |
|
---------- |
|
|
|
This attribute excludes the hypervisor. |
|
|
|
For a VHE host this attribute is ignored as we consider the host kernel to |
|
be the hypervisor. |
|
|
|
For a non-VHE host this attribute will exclude EL2 as we consider the |
|
hypervisor to be any code that runs at EL2 which is predominantly used for |
|
guest/host transitions. |
|
|
|
For the guest this attribute has no effect. Please note that EL2 is |
|
never counted within a guest. |
|
|
|
|
|
exclude_host / exclude_guest |
|
---------------------------- |
|
|
|
These attributes exclude the KVM host and guest, respectively. |
|
|
|
The KVM host may run at EL0 (userspace), EL1 (non-VHE kernel) and EL2 (VHE |
|
kernel or non-VHE hypervisor). |
|
|
|
The KVM guest may run at EL0 (userspace) and EL1 (kernel). |
|
|
|
Due to the overlapping exception levels between host and guests we cannot |
|
exclusively rely on the PMU's hardware exception filtering - therefore we |
|
must enable/disable counting on the entry and exit to the guest. This is |
|
performed differently on VHE and non-VHE systems. |
|
|
|
For non-VHE systems we exclude EL2 for exclude_host - upon entering and |
|
exiting the guest we disable/enable the event as appropriate based on the |
|
exclude_host and exclude_guest attributes. |
|
|
|
For VHE systems we exclude EL1 for exclude_guest and exclude both EL0,EL2 |
|
for exclude_host. Upon entering and exiting the guest we modify the event |
|
to include/exclude EL0 as appropriate based on the exclude_host and |
|
exclude_guest attributes. |
|
|
|
The statements above also apply when these attributes are used within a |
|
non-VHE guest however please note that EL2 is never counted within a guest. |
|
|
|
|
|
Accuracy |
|
-------- |
|
|
|
On non-VHE hosts we enable/disable counters on the entry/exit of host/guest |
|
transition at EL2 - however there is a period of time between |
|
enabling/disabling the counters and entering/exiting the guest. We are |
|
able to eliminate counters counting host events on the boundaries of guest |
|
entry/exit when counting guest events by filtering out EL2 for |
|
exclude_host. However when using !exclude_hv there is a small blackout |
|
window at the guest entry/exit where host events are not captured. |
|
|
|
On VHE systems there are no blackout windows.
|
|
|