[Xen-devel] [PATCH v8 13/13] docs: add xl-psr.markdown

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

Add document to introduce basic concepts and terms in PSR family
technologies and the xl interfaces.

Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
Changes in v7:
* Correct 'xl psr-hwinfo'.
Changes in v6:
* Address comments from Ian.
Changes in v5:
* Address comments from Andrew/Ian.
---
 docs/man/xl.pod.1         |   7 ++-
 docs/misc/xl-psr.markdown | 133 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 139 insertions(+), 1 deletion(-)
 create mode 100644 docs/misc/xl-psr.markdown

diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
index 4dd5388..1fe3ac4 100644
--- a/docs/man/xl.pod.1
+++ b/docs/man/xl.pod.1
@@ -1490,6 +1490,9 @@ Intel Haswell and later server platforms offer shared 
resource monitoring
 and control technologies. The availability of these technologies and the
 hardware capabilities can be shown with B<psr-hwinfo>.
 
+See L<http://xenbits.xen.org/docs/unstable/misc/xl-psr.html> for more
+information.
+
 =over 4
 
 =item B<psr-hwinfo> [I<OPTIONS>]
@@ -1561,7 +1564,8 @@ on VM basis. To enforce cache on a specific domain, just 
set capacity bitmasks
 
 =item B<psr-cat-cbm-set> [I<OPTIONS>] I<domain-id> I<cbm>
 
-Set cache capacity bitmasks(CBM) for a domain.
+Set cache capacity bitmasks(CBM) for a domain. For how to specify I<cbm>
+please refer to L<http://xenbits.xen.org/docs/unstable/misc/xl-psr.html>.
 
 B<OPTIONS>
 
@@ -1602,6 +1606,7 @@ And the following documents on the xen.org website:
 L<http://xenbits.xen.org/docs/unstable/misc/xl-network-configuration.html>
 L<http://xenbits.xen.org/docs/unstable/misc/xl-disk-configuration.txt>
 L<http://xenbits.xen.org/docs/unstable/misc/xsm-flask.txt>
+L<http://xenbits.xen.org/docs/unstable/misc/xl-psr.html>
 
 For systems that don't automatically bring CPU online:
 
diff --git a/docs/misc/xl-psr.markdown b/docs/misc/xl-psr.markdown
new file mode 100644
index 0000000..3545912
--- /dev/null
+++ b/docs/misc/xl-psr.markdown
@@ -0,0 +1,133 @@
+# Intel Platform Shared Resource Monitoring/Control in xl
+
+This document introduces Intel Platform Shared Resource Monitoring/Control
+technologies, their basic concepts and the xl interfaces.
+
+## Cache Monitoring Technology (CMT)
+
+Cache Monitoring Technology (CMT) is a new feature available on Intel Haswell
+and later server platforms that allows an OS or Hypervisor/VMM to determine
+the usage of cache (currently only L3 cache supported) by applications running
+on the platform. A Resource Monitoring ID (RMID) is the abstraction of the
+application(s) that will be monitored for its cache usage. The CMT hardware
+tracks cache utilization of memory accesses according to the RMID and reports
+monitored data via a counter register.
+
+For more detailed information please refer to Intel SDM chapter
+"17.14 - Platform Shared Resource Monitoring: Cache Monitoring Technology".
+
+In Xen's implementation, each domain in the system can be assigned a RMID
+independently, while RMID=0 is reserved for monitoring domains that don't
+have CMT service attached. RMID is opaque for xl/libxl and is only used in
+hypervisor.
+
+### xl interfaces
+
+A domain is assigned a RMID implicitly by attaching it to CMT service:
+
+`xl psr-cmt-attach <domid>`
+
+After that, cache usage for the domain can be shown by:
+
+`xl psr-cmt-show cache-occupancy <domid>`
+
+Once monitoring is not needed any more, the domain can be detached from the
+CMT service by:
+
+`xl psr-cmt-detach <domid>`
+
+An attach may fail because of no free RMID available. In such case unused
+RMID(s) can be freed by detaching corresponding domains from CMT service.
+
+Maximum RMID and supported monitor types in the system can be obtained by:
+
+`xl psr-hwinfo --cmt`
+
+## Memory Bandwidth Monitoring (MBM)
+
+Memory Bandwidth Monitoring(MBM) is a new hardware feature available on Intel
+Broadwell and later server platforms which builds on the CMT infrastructure to
+allow monitoring of system memory bandwidth. It introduces two new monitoring
+event type to monitor system total/local memory bandwidth. The same RMID can
+be used to monitor both cache usage and memory bandwidth at the same time.
+
+For more detailed information please refer to Intel SDM chapter
+"17.14 - Platform Shared Resource Monitoring: Cache Monitoring Technology".
+
+In Xen's implementation, MBM shares the same set of underlying monitoring
+service with CMT and can be used to monitor memory bandwidth on a per domain
+basis.
+
+The xl interfaces are the same with that of CMT. The difference is the
+monitor type is corresponding memory monitoring type (local-mem-bandwidth/
+total-mem-bandwidth instead of cache-occupancy). E.g. after a `xl 
psr-cmt-attach`:
+
+`xl psr-cmt-show local-mem-bandwidth <domid>`
+
+`xl psr-cmt-show total-mem-bandwidth <domid>`
+
+## Cache Allocation Technology (CAT)
+
+Cache Allocation Technology (CAT) is a new feature available on Intel
+Broadwell and later server platforms that allows an OS or Hypervisor/VMM to
+partition cache allocation (i.e. L3 cache) based on application priority or
+Class of Service (COS). Each COS is configured using capacity bitmasks (CBM)
+which represent cache capacity and indicate the degree of overlap and
+isolation between classes. System cache resource is divided into numbers of
+minimum portions which is then made up into subset for cache partition. Each
+portion corresponds to a bit in CBM and the set bit represents the
+corresponding cache portion is available.
+
+For example, assuming a system with 8 portions and 3 domains:
+
+ * A CBM of 0xff for every domain means each domain can access the whole cache.
+   This is the default.
+
+ * Giving one domain a CBM of 0x0f and the other two domain's 0xf0 means that
+   the first domain gets exclusive access to half of the cache (half of the
+   portions) and the other two will share the other half.
+
+ * Giving one domain a CBM of 0x0f, one 0x30 and the last 0xc0 would give the
+   first domain exclusive access to half the cache, and the other two exclusive
+   access to one quarter each.
+
+For more detailed information please refer to Intel SDM chapter
+"17.15 - Platform Shared Resource Control: Cache Allocation Technology".
+
+In Xen's implementation, CBM can be configured with libxl/xl interfaces but
+COS is maintained in hypervisor only. The cache partition granularity is per
+domain, each domain has COS=0 assigned by default, the corresponding CBM is
+all-ones, which means all the cache resource can be used by default.
+
+### xl interfaces
+
+System CAT information such as maximum COS and CBM length can be obtained by:
+
+`xl psr-hwinfo --cat`
+
+The simplest way to change a domain's CBM from its default is running:
+
+`xl psr-cat-cbm-set  [OPTIONS] <domid> <cbm>`
+
+where cbm is a number to represent the corresponding cache subset can be used.
+A cbm is valid only when:
+
+ * Set bits only exist in the range of [0, cbm_len), where cbm_len can be
+   obtained with `xl psr-hwinfo --cat`.
+ * All the set bits are contiguous.
+
+In a multi-socket system, the same cbm will be set on each socket by default.
+Per socket cbm can be specified with the `--socket SOCKET` option.
+
+Setting the CBM may not be successful if insufficient COS is available. In
+such case unused COS(es) may be freed by setting CBM of all related domains to
+its default value(all-ones).
+
+Per domain CBM settings can be shown by:
+
+`xl psr-cat-show`
+
+## Reference
+
+[1] Intel SDM
+(http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html).
-- 
1.9.1


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