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Re: [libvirt] [PATCHv7 00/18] Introduce x86 Cache Monitoring Technology (CMT)




On 10/22/18 4:01 AM, Wang Huaqiang wrote:
> This series of patches and the series already been merged introduce
> the x86 Cache Monitoring Technology (CMT) to libvirt by interacting
> with kernel resource control (resctrl) interface. CMT is one of the
> Intel(R) x86 CPU feature which belongs to the Resource Director
> Technology (RDT). CMT reports the occupancy of the last level cache,
> which is shared by all CPU cores.
> 

Rather than top or bottom post ;-) - as noted during the reviewing -
many of the patches are fine; however, once we get to the meat in patch
12 and beyond I think more adjustment is necessary. I wouldn't want to
introduce the XML from patch 12, but have no teeth behind it from the
remaining patches.

Getting closer, but not quite there yet.  If you're good with my
proposed adjustments for patches 1-11, then I can get those pushed so
that we can make some progress.

On your next round, please let's try to get a news.xml to summarize the
changes added at the end. Saves me from chasing later on.

I won't have a lot of cycles for the rest of the week to debate or
provide feedback. I'm in class Wed -> Fri.  I really don't think the
comments I've provided in the later patches are that controversial.

I do think we probably need a way to handle the Unplug with the existing
usage of the *tasks file before we go too far and add monitor. You also
need to figure a way to not add the same pid twice. I realize now that a
*Remove operation will remove the *tasks file from a $path so some
concerns I had were at least reduced.

John


> In the v1 series, an original and complete feature for CMT was introduced
> The v2 and v3 patches address the feature for the host capability of CMT.
> v4 is addressing the feature for monitoring VM vcpu thread set cache
> occupancy and reporting it through a virsh command.
> 
> We have serval discussion about the enabling of CMT, please refer to
> following links for the RFCs.
> RFCv3
> https://www.redhat.com/archives/libvir-list/2018-August/msg01213.html
> RFCv2
> https://www.redhat.com/archives/libvir-list/2018-July/msg00409.html
> https://www.redhat.com/archives/libvir-list/2018-July/msg01241.html
> RFCv1
> https://www.redhat.com/archives/libvir-list/2018-June/msg00674.html
> 
> And the merged commits are list as below, for host capability of CMT.
> 6af8417415508c31f8ce71234b573b4999f35980
> 8f6887998bf63594ae26e3db18d4d5896c5f2cb4
> 58fcee6f3a2b7e89c21c1fb4ec21429c31a0c5b8
> 12093f1feaf8f5023dcd9d65dff111022842183d
> a5d293c18831dcf69ec6195798387fbb70c9f461
> 
> 
> 1. About reason why CMT is necessary in libvirt?
> The perf events of 'CMT, MBML, MBMT' have been phased out since Linux
> kernel commit c39a0e2c8850f08249383f2425dbd8dbe4baad69, in libvirt
> the perf based cmt,mbm will not work with the latest linux kernel. These
> patches add CMT feature to libvirt through kernel resctrlfs interface.
> 
> 2 Create cache monitoring group (cache monitor).
> 
>     The main interface for creating monitoring group is through XML file. The
> proposed configuration is like:
> 
>       <cputune>
>         <cachetune vcpus='1'>
>           <cache id='0' level='3' type='code' size='7680' unit='KiB'/>
>           <cache id='1' level='3' type='data' size='3840' unit='KiB'/>
>     +     <monitor level='3' vcpus='1'/>
>         </cachetune>
>         <cachetune vcpus='4-7'>
>     +     <monitor level='3' vcpus='4-6'/>
>         </cachetune>
>       </cputune>
> 
> In above XML, created 2 cache resctrl allocation groups and 2 resctrl
> monitoring groups.
> The changes of cache monitor will be effective in next booting of VM.
> 
> 2 Show CMT result through command 'domstats'
> 
> Adding the interface in qemu to report this information for resource
> monitor group through command 'virsh domstats --cpu-total'.
> Below is a typical output:
> 
>      # virsh domstats 1 --cpu-total
>      Domain: 'ubuntu16.04-base'
>      ...
>        cpu.cache.monitor.count=2
>        cpu.cache.monitor.0.name=vcpus_1
>        cpu.cache.monitor.0.vcpus=1
>        cpu.cache.monitor.0.bank.count=2
>        cpu.cache.monitor.0.bank.0.id=0
>        cpu.cache.monitor.0.bank.0.bytes=4505600
>        cpu.cache.monitor.0.bank.1.id=1
>        cpu.cache.monitor.0.bank.1.bytes=5586944
>        cpu.cache.monitor.1.name=vcpus_4-6
>        cpu.cache.monitor.1.vcpus=4,5,6
>        cpu.cache.monitor.1.bank.count=2
>        cpu.cache.monitor.1.bank.0.id=0
>        cpu.cache.monitor.1.bank.0.bytes=17571840
>        cpu.cache.monitor.1.bank.1.id=1
>        cpu.cache.monitor.1.bank.1.bytes=29106176
> 
> Changes in v7:
> - Add several lines removed by mistake.
> 
> Changes in v6:
> - Addressing John's review comments for v5.
> - Removed and cleaned the concepts of 'default allocation' and
> 'default monitor'.
> - qemu: virsh domstats --cpu-total output for CMT, add identifier
> 'monitor' for each itm.
> 
> Changes in v5:
> - qemu: Setting up vcpu and adding pids to resctrl monitor groups during
> re-connection.
> - Add the document for domain configuration related to resctrl monitor.
> 
> Changes in v4:
> v4 is addressing the feature for monitoring VM vcpu
> thread set cache occupancy and reporting it through a
> virsh command.
> - Introduced resctrl default allocation
> - Introduced resctrl monitor and default monitor
> 
> Changes in v3:
> - Addressed John Ferlan's review.
> - Typo fixed.
> - Removed VIR_ENUM_DECL(virMonitor);
> 
> Changes in v2:
> - Introduced MBM capability.
> - Capability layout changed
>     * Moved <monitor> from cahe <bank> to <cache>
>     * Renamed <Threshold> to <reuseThreshold>
> - Document for 'reuseThreshold' changed.
> - Introduced API virResctrlInfoGetMonitorPrefix
> - Added more tests, covering standalone CMT, fake new
>   feature.
> - Creating CMT resource control group will be
>   subsequent job.
> 
> Wang Huaqiang (18):
>   docs,util: Refactor schemas and virresctrl to support optional cache
>   util: Introduce resctrl monitor for CMT
>   util: Refactor code for determining allocation path
>   util: Add interface to determine monitor path
>   util: Refactor code for adding PID to the resource group
>   util: Add interface for adding PID to the monitor
>   util: Refactor code for creating resctrl group
>   util: Add interface for creating monitor group
>   util: Add more interfaces for resctrl monitor
>   conf: Remove virDomainResctrlAppend and introduce virDomainResctrlNew
>   conf: move virResctrlAllocIsEmpty to a place a litter lower
>   conf: Introduce cache monitor element in cachetune
>   qemu: enable resctrl monitor in qemu
>   util: Add function for checking if monitor is running
>   conf: Add 'id' to virDomainResctrlDef
>   qemu: refactor qemuDomainGetStatsCpu
>   qemu: Report cache occupancy (CMT) with domstats
>   qemu: Setting up vcpu and adding pids to resctrl monitor groups during
>     reconnection
> 
>  docs/formatdomain.html.in                          |  30 +-
>  docs/schemas/domaincommon.rng                      |  14 +-
>  src/conf/domain_conf.c                             | 310 ++++++++++--
>  src/conf/domain_conf.h                             |  12 +
>  src/libvirt-domain.c                               |   9 +
>  src/libvirt_private.syms                           |  11 +
>  src/qemu/qemu_driver.c                             | 270 +++++++++-
>  src/qemu/qemu_process.c                            |  69 ++-
>  src/util/virresctrl.c                              | 560 +++++++++++++++++++--
>  src/util/virresctrl.h                              |  49 ++
>  tests/genericxml2xmlindata/cachetune-cdp.xml       |   3 +
>  .../cachetune-colliding-monitor.xml                |  30 ++
>  tests/genericxml2xmlindata/cachetune-small.xml     |   7 +
>  tests/genericxml2xmltest.c                         |   2 +
>  14 files changed, 1283 insertions(+), 93 deletions(-)
>  create mode 100644 tests/genericxml2xmlindata/cachetune-colliding-monitor.xml
> 


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