[Xen-devel] [PATCH v4 4/4] docs: add document to introduce CDP command

[He Chen <he.chen@xxxxxxxxxxxxxxx>]

Add new CDP options with CAT commands in xl interface man page.
Add description of CDP in xl-psr.markdown.

Signed-off-by: He Chen <he.chen@xxxxxxxxxxxxxxx>
---
 docs/man/xl.pod.1         | 14 ++++++++++++++
 docs/misc/xl-psr.markdown | 44 +++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
index f22c3f3..3c7107d 100644
--- a/docs/man/xl.pod.1
+++ b/docs/man/xl.pod.1
@@ -1530,6 +1530,12 @@ applications. In the Xen implementation, CAT is used to 
control cache allocation
 on VM basis. To enforce cache on a specific domain, just set capacity bitmasks
 (CBM) for the domain.
 
+Intel Broadwell and later server platforms also offer Code/Data Prioritization
+(CDP) for cache allocation, which support specifying code or data cache for
+applications. CDP is used on VM basis in the Xen implementation. To specify
+code or data CBM for the domain, CDP feature must be enabled and CBM type
+options need to be specified when setting CBM.
+
 =over 4
 
 =item B<psr-cat-cbm-set> [I<OPTIONS>] I<domain-id> I<cbm>
@@ -1545,6 +1551,14 @@ B<OPTIONS>
 
 Specify the socket to process, otherwise all sockets are processed.
 
+=item B<-c>, B<--code>
+
+Set code CBM when CDP is enabled.
+
+=item B<-d>, B<--data>
+
+Set data CBM when CDP is enabled.
+
 =back
 
 =item B<psr-cat-show> [I<domain-id>]
diff --git a/docs/misc/xl-psr.markdown b/docs/misc/xl-psr.markdown
index 3545912..5eb97cc 100644
--- a/docs/misc/xl-psr.markdown
+++ b/docs/misc/xl-psr.markdown
@@ -14,7 +14,7 @@ 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".
+"17.15 - 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
@@ -91,17 +91,42 @@ For example, assuming a system with 8 portions and 3 
domains:
    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.
 
+Code/Data Prioritization (CDP) Technology is an extension of CAT, which is
+available on Intel Broadwell and later server platforms. CDP enables isolation
+and separate prioritization of code and data fetches to the L3 cache in a
+software configurable manner, which can enable workload prioritization and
+tuning of cache capacity to the characteristics of the workload. CDP extends
+Cache Allocation Technology (CAT) by providing separate code and data masks
+per Class of Service (COS).
+
+CDP can be enabled by adding `psr=cdp` to Xen bootline.
+
+When CDP is enabled,
+
+ * the CAT masks are re-mapped into interleaved pairs of masks for data or code
+   fetches.
+
+ * the range of COS for CAT is re-indexed, with the lower-half of the COS
+   range available for CDP.
+
+CDP allows OS or Hypervisor to partition cache allocation more fine-grained,
+code cache and data cache can be specified respectively. With CDP enabled,
+one COS corresponds to two CBMs (code CBM & data CBM), since the sum of CBMs
+is fixed, that means the number of available COSes will reduce to half when
+CDP is on.
+
+For more detailed information please refer to Intel SDM chapter
+"17.16 - Platform Shared Resource Control: Cache Allocation Technology".
+
 ### xl interfaces
 
-System CAT information such as maximum COS and CBM length can be obtained by:
+System CAT information such as maximum COS, CBM length and CDP status can be
+obtained by:
 
 `xl psr-hwinfo --cat`
 
@@ -116,6 +141,15 @@ A cbm is valid only when:
    obtained with `xl psr-hwinfo --cat`.
  * All the set bits are contiguous.
 
+When CDP is enabled, `-c` or `--code` option is available to set code CBM for
+the domain.
+
+When CDP is enabled, `-d` or `--data` option is available to set data CBM for
+the domain.
+
+If neither `-c` nor `-d` option is specified when CDP is on, the same code CBM
+and data CBM will be set for the domain.
+
 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.
 
-- 
1.9.1


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