4:02 a.m.
This is an RFC request for supporting CPU Cache Monitoring Technology (CMT) feature in
libvirt. Since MBM is also another feature which is very close to CMT, for simplicity we
only discuss CMT here. MBM is the followup that will be implemented after CMT.
About CMT please refer to Intel x86 SDM section 17.18 of volume 3
(link:https://software.intel.com/en-us/articles/intel-sdm).
## About '_virResctrlMon' interface
The cache allocation technology (CAT) has already been implemented in util/virresctrl.*
which interacts with Linux kernel resctrl file system. Very simlimar to CAT, the CMT
object is represented by 'struct _virResctrlMon', which is
```
struct _virResctrlMon {
virObject parent;
/* pairedalloc: pointer to a resctrl allocaion it paried with.
* NULL for a resctrl monitoring group not associated with
* any allocation. */
virResctrlAllocPtr pairedalloc;
/* The identifier (any unique string for now) */
char *id;
/* libvirt-generated path, may be identical to alloction path
* may not if allocation is ready */
char *path;
};
```
Almost following the same logic behind '_virResctrlAlloc' which is mainly
presented in file 'virresctrl.c', a group of APIs has been designed to manipulate
'_virResctrlMon'. The '_virResctrlMon' shares a lot in common with
'_virResctrlAlloc' except field 'pairedalloc'.
'pairedalloc' stores the pointer of paired resctrl allocation object. With current
libvirt resctrl implementation, if a resctrl '_virResctrlAlloc' object is created,
the CMT hardware is enabled automatically and shares the same folder under same resctrlfs,
I call the CMT '_virResctrlMon' object that shares the same folder under resctrlfs
as 'paired' _virResctrlMon, further, one '_virResctrlMon' and one
'_virResctrlAlloc' are a pare. In '_virResctrlMon' the paired
'_virResctrlAlloc' is tracked through pairedalloc. paired mon group could not be
dynamically enabled or disabled during runtime.
'pairedalloc' could be set to NULL, which creates a non-paired mon group object.
Which is necessory because CMT could work independently to monitor the utilization of
critical CPU resouces (cache or memory bandwidth) without allocating any dedicated cache
or memory bandwidth. A non-paired mon group object represents an independent working CMT.
Non-paired mon group could be enabled or disabled during runtime.
## About virsh command 'resctrl'
To set or get the resctrl mon group (hardware CMT), a virsh command 'resctrl' is
created. here are the common usages:
```
[root@dl-c200 david]# virsh list --all
Id Name State
----------------------------------------------------
1 vm3 running
3 vm2 running
- vm1 shut off
```
### Test on a running domain vm3
To get RDT monitoring status, type 'virsh resctrl <domain>'
```
[root@dl-c200 david]# virsh resctrl vm3
RDT Monitoring Status: Enabled
```
To enable RDT monitoring, type 'virsh resctrl <domain> --enable'
```
[root@dl-c200 david]# virsh resctrl vm3 --enable
RDT Monitoring Status: Enabled
```
To diable RDT monitoring, type 'virsh resctrl <domain> --disable'
```
[root@dl-c200 david]# virsh resctrl vm3 --disable
RDT Monitoring Status: Disabled
[root@dl-c200 david]# virsh resctrl vm3
RDT Monitoring Status: Disabled
```
### test on domain not running vm1
if domain is not active, it will fail to set RDT monitoring status, and also get the state
of 'disabled'
```
[root@dl-c200 david]# virsh resctrl vm1
RDT Monitoring Status: Disabled
[root@dl-c200 david]# virsh resctrl vm1 --enable
error: Requested operation is not valid: domain is not running
[root@dl-c200 david]# virsh resctrl vm1 --disable
error: Requested operation is not valid: domain is not running
```
### test on domain vm2
domain vm2 is active and the CAT functionality is enabled through 'cachetune'
(configured in 'cputune/cachetune' section). So the resctrl mon group is a
'paried' one, for 'pared' mon group, the RDT monitoring could not be
disabled. If it is allowed to disable 'paire' mon group, we have to destroy
resctrl allocation folders which is not supported by current cache allocation design.
```
[root@dl-c200 libvirt]# virsh resctrl vm2 --enable
RDT Monitoring Status: Enabled (forced by cachetune)
[root@dl-c200 libvirt]# virsh resctrl vm2 --disable
RDT Monitoring Status: Enabled (forced by cachetune)
[root@dl-c200 libvirt]# virsh resctrl vm2
RDT Monitoring Status: Enabled (forced by cachetune)
```
## About showing the utilization information of RDT
A domstats field has been created to show the utilization of RDT resources, the command is
like this:
```
[root@dl-c200 libvirt]# virsh domstats --resctrl
Domain: 'vm1'
resctrl.cmt=0
Domain: 'vm3'
resctrl.cmt=180224
Domain: 'vm2'
resctrl.cmt=2613248
```
Wang Huaqiang (3):
util: add Intel x86 RDT/CMT support
tools: virsh: add command for controling/monitoring resctrl
tools: virsh domstats: show RDT CMT resource utilization information
include/libvirt/libvirt-domain.h | 10 ++
src/conf/domain_conf.c | 28 ++++
src/conf/domain_conf.h | 3 +
src/driver-hypervisor.h | 8 +
src/libvirt-domain.c | 92 +++++++++++
src/libvirt_private.syms | 9 +
src/libvirt_public.syms | 6 +
src/qemu/qemu_driver.c | 189 +++++++++++++++++++++
src/qemu/qemu_process.c | 65 +++++++-
src/remote/remote_daemon_dispatch.c | 45 +++++
src/remote/remote_driver.c | 2 +
src/remote/remote_protocol.x | 28 +++-
src/remote_protocol-structs | 12 ++
src/util/virresctrl.c | 316 +++++++++++++++++++++++++++++++++++-
src/util/virresctrl.h | 44 +++++
tools/virsh-domain-monitor.c | 7 +
tools/virsh-domain.c | 74 +++++++++
17 files changed, 933 insertions(+), 5 deletions(-)
--
2.7.4