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Date: Tue, 11 Oct 2022 16:06:29 +0700
From: Bagas Sanjaya <bagasdotme@...il.com>
To: Babu Moger <babu.moger@....com>
Cc: corbet@....net, reinette.chatre@...el.com, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, fenghua.yu@...el.com,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
paulmck@...nel.org, akpm@...ux-foundation.org,
quic_neeraju@...cinc.com, rdunlap@...radead.org,
damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
eranian@...gle.com
Subject: Re: [PATCH v6 12/12] Documentation/x86: Update resctrl_ui.rst for
new features
On Mon, Oct 10, 2022 at 03:30:40PM -0500, Babu Moger wrote:
> diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
> index 71a531061e4e..e2a59249d183 100644
> --- a/Documentation/x86/resctrl.rst
> +++ b/Documentation/x86/resctrl.rst
> @@ -17,14 +17,16 @@ AMD refers to this feature as AMD Platform Quality of Service(AMD QoS).
> This feature is enabled by the CONFIG_X86_CPU_RESCTRL and the x86 /proc/cpuinfo
> flag bits:
>
> -============================================= ================================
> +=============================================== ================================
> RDT (Resource Director Technology) Allocation "rdt_a"
> CAT (Cache Allocation Technology) "cat_l3", "cat_l2"
> CDP (Code and Data Prioritization) "cdp_l3", "cdp_l2"
> CQM (Cache QoS Monitoring) "cqm_llc", "cqm_occup_llc"
> MBM (Memory Bandwidth Monitoring) "cqm_mbm_total", "cqm_mbm_local"
> MBA (Memory Bandwidth Allocation) "mba"
> -============================================= ================================
> +SMBA (Slow Memory Bandwidth Allocation) "smba"
> +BMEC (Bandwidth Monitoring Event Configuration) "bmec"
> +=============================================== ================================
>
> To use the feature mount the file system::
>
> @@ -161,6 +163,79 @@ with the following files:
> "mon_features":
> Lists the monitoring events if
> monitoring is enabled for the resource.
> + Example::
> +
> + # cat /sys/fs/resctrl/info/L3_MON/mon_features
> + llc_occupancy
> + mbm_total_bytes
> + mbm_local_bytes
> +
> + If the system supports Bandwidth Monitoring Event
> + Configuration (BMEC), then the bandwidth events will
> + be configurable. The output will be::
> +
> + # cat /sys/fs/resctrl/info/L3_MON/mon_features
> + llc_occupancy
> + mbm_total_bytes
> + mbm_total_config
> + mbm_local_bytes
> + mbm_local_config
> +
> +"mbm_total_config", "mbm_local_config":
> + These files contain the current event configuration for the events
> + mbm_total_bytes and mbm_local_bytes, respectively, when the
> + Bandwidth Monitoring Event Configuration (BMEC) feature is supported.
> + The event configuration settings are domain specific and will affect
> + all the CPUs in the domain.
> +
> + Following are the types of events supported:
> +
> + ==== ========================================================
> + Bits Description
> + ==== ========================================================
> + 6 Dirty Victims from the QOS domain to all types of memory
> + 5 Reads to slow memory in the non-local NUMA domain
> + 4 Reads to slow memory in the local NUMA domain
> + 3 Non-temporal writes to non-local NUMA domain
> + 2 Non-temporal writes to local NUMA domain
> + 1 Reads to memory in the non-local NUMA domain
> + 0 Reads to memory in the local NUMA domain
> + ==== ========================================================
> +
> + By default, the mbm_total_bytes configuration is set to 0x7f to count
> + all the event types and the mbm_local_bytes configuration is set to
> + 0x15 to count all the local memory events.
> +
> + Examples:
> +
> + * To view the current configuration::
> + ::
> +
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_total_config
> + 0=0x7f;1=0x7f;2=0x7f;3=0x7f
> +
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_local_config
> + 0=0x15;1=0x15;3=0x15;4=0x15
> +
> + * To change the mbm_total_bytes to count only reads on domain 0.
> + To achieve this, the bits 0, 1, 4 and 5 needs to be set which is
> + 110011b (in hex 0x33).
> + ::
> +
> + # echo "0=0x33" > /sys/fs/resctrl/info/L3_MON/mbm_total_config
> +
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_total_config
> + 0=0x33;1=0x7f;2=0x7f;3=0x7f
> +
> + * To change the mbm_local_bytes to count all the slow memory reads
> + on domain 1. To achieve this, the bits 4 and 5 needs to be set
> + which is 110000b (in hex 0x30).
> + ::
> +
> + # echo "1=0x30" > /sys/fs/resctrl/info/L3_MON/mbm_local_config
> +
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_local_config
> + 0=0x15;1=0x30;3=0x15;4=0x15
>
> "max_threshold_occupancy":
> Read/write file provides the largest value (in
> @@ -464,6 +539,25 @@ Memory bandwidth domain is L3 cache.
>
> MB:<cache_id0>=bw_MBps0;<cache_id1>=bw_MBps1;...
>
> +Slow Memory bandwidth Allocation (SMBA)
> +-------------------------------------------------
> +AMD hardware can support slow Memory bandwidth Allocation feature.
> +Currently, CXL.memory is the only supported "slow" memory device.
> +With the support of SMBA feature the hardware enables bandwidth
> +allocation on the slow memory devices. If there are multiple slow
> +memory devices in the system, then the throttling logic groups all
> +the slow sources together and applies the limit on them as a whole.
> +
> +The presence of the SMBA feature(with CXL.memory) is independent
> +of whether slow memory device is actually present in the system.
> +If there is no slow memory in the system, then setting a SMBA limit
> +will have no impact on the performance of the system.
> +
> +Slow Memory bandwidth domain is L3 cache.
> +::
> +
> + SMBA:<cache_id0>=bandwidth0;<cache_id1>=bandwidth1;...
> +
> Reading/writing the schemata file
> ---------------------------------
> Reading the schemata file will show the state of all resources
> @@ -479,6 +573,44 @@ which you wish to change. E.g.
> L3DATA:0=fffff;1=fffff;2=3c0;3=fffff
> L3CODE:0=fffff;1=fffff;2=fffff;3=fffff
>
> +Reading/writing the schemata file (on AMD systems)
> +--------------------------------------------------
> +Reading the schemata file will show the state of all resources
> +on all domains. When writing the memory bandwidth allocation you
> +only need to specify those values in an absolute number expressed
> +in 1/8 GB/s increments. To allocate bandwidth limit of 2GB, you
> +need to specify the value 16 (16 * 1/8 = 2). For example:
> +::
> +
> + # cat schemata
> + MB:0=2048;1=2048;2=2048;3=2048
> + L3:0=ffff;1=ffff;2=ffff;3=ffff
> +
> + # echo "MB:1=16" > schemata
> + # cat schemata
> + MB:0=2048;1= 16;2=2048;3=2048
> + L3:0=ffff;1=ffff;2=ffff;3=ffff
> +
> +Reading/writing the schemata file (on AMD systems) with SMBA feature
> +-------------------------------------------------------------------
The heading above produces htmldocs warnings:
Documentation/x86/resctrl.rst:595: WARNING: Title underline too short.
Reading/writing the schemata file (on AMD systems) with SMBA feature
-------------------------------------------------------------------
Documentation/x86/resctrl.rst:595: WARNING: Title underline too short.
Reading/writing the schemata file (on AMD systems) with SMBA feature
-------------------------------------------------------------------
I have applied the fixup:
---- >8 ----
diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
index e2a59249d18322..145916828f2bae 100644
--- a/Documentation/x86/resctrl.rst
+++ b/Documentation/x86/resctrl.rst
@@ -592,7 +592,7 @@ need to specify the value 16 (16 * 1/8 = 2). For example:
L3:0=ffff;1=ffff;2=ffff;3=ffff
Reading/writing the schemata file (on AMD systems) with SMBA feature
--------------------------------------------------------------------
+--------------------------------------------------------------------
Reading the schemata file will show the state of all resources
on all domains. When writing the memory bandwidth allocation you
only need to specify those values in an absolute number expressed
> +Reading the schemata file will show the state of all resources
> +on all domains. When writing the memory bandwidth allocation you
> +only need to specify those values in an absolute number expressed
> +in 1/8 GB/s increments. To allocate bandwidth limit of 8GB, you
> +need to specify the value 64 (64 * 1/8 = 8). E.g.
> +::
> +
> + # cat schemata
> + SMBA:0=2048;1=2048;2=2048;3=2048
> + MB:0=2048;1=2048;2=2048;3=2048
> + L3:0=ffff;1=ffff;2=ffff;3=ffff
> +
> + # echo "SMBA:1=64" > schemata
> + # cat schemata
> + SMBA:0=2048;1= 64;2=2048;3=2048
> + MB:0=2048;1=2048;2=2048;3=2048
> + L3:0=ffff;1=ffff;2=ffff;3=ffff
> +
> Cache Pseudo-Locking
> ====================
> CAT enables a user to specify the amount of cache space that an
>
>
The rest of prose can be improved:
---- >8 ----
diff --git a/Documentation/x86/resctrl.rst b/Documentation/x86/resctrl.rst
index 145916828f2bae..92b2c4e03a4a26 100644
--- a/Documentation/x86/resctrl.rst
+++ b/Documentation/x86/resctrl.rst
@@ -217,9 +217,9 @@ with the following files:
# cat /sys/fs/resctrl/info/L3_MON/mbm_local_config
0=0x15;1=0x15;3=0x15;4=0x15
- * To change the mbm_total_bytes to count only reads on domain 0.
- To achieve this, the bits 0, 1, 4 and 5 needs to be set which is
- 110011b (in hex 0x33).
+ * To change the mbm_total_bytes to count only reads on domain 0
+ (the bits 0, 1, 4 and 5 needs to be set, which means 110011b
+ {in hex 0x33}):
::
# echo "0=0x33" > /sys/fs/resctrl/info/L3_MON/mbm_total_config
@@ -228,8 +228,8 @@ with the following files:
0=0x33;1=0x7f;2=0x7f;3=0x7f
* To change the mbm_local_bytes to count all the slow memory reads
- on domain 1. To achieve this, the bits 4 and 5 needs to be set
- which is 110000b (in hex 0x30).
+ on domain 1 (the bits 4 and 5 needs to be set, which means 110000b
+ {in hex 0x30}):
::
# echo "1=0x30" > /sys/fs/resctrl/info/L3_MON/mbm_local_config
@@ -540,20 +540,21 @@ Memory bandwidth domain is L3 cache.
MB:<cache_id0>=bw_MBps0;<cache_id1>=bw_MBps1;...
Slow Memory bandwidth Allocation (SMBA)
--------------------------------------------------
-AMD hardware can support slow Memory bandwidth Allocation feature.
+---------------------------------------
+AMD hardwares support Slow Memory bandwidth Allocation (SMBA) feature.
Currently, CXL.memory is the only supported "slow" memory device.
-With the support of SMBA feature the hardware enables bandwidth
-allocation on the slow memory devices. If there are multiple slow
-memory devices in the system, then the throttling logic groups all
-the slow sources together and applies the limit on them as a whole.
+With the support of SMBA, the hardware enables bandwidth allocation
+on the slow memory devices. If there are multiple such devices in the
+system, the throttling logic groups all the slow sources together
+and applies the limit on them as a whole.
-The presence of the SMBA feature(with CXL.memory) is independent
-of whether slow memory device is actually present in the system.
-If there is no slow memory in the system, then setting a SMBA limit
-will have no impact on the performance of the system.
+The presence of SMBA (with CXL.memory) is independent of slow memory
+devices presence. If there is no such devices on the system, then
+setting the configuring SMBA will have no impact on the performance
+of the system.
-Slow Memory bandwidth domain is L3 cache.
+The bandwidth domain for slow memory is L3 cache. Its schemata file
+is formatted as:
::
SMBA:<cache_id0>=bandwidth0;<cache_id1>=bandwidth1;...
@@ -575,11 +576,13 @@ which you wish to change. E.g.
Reading/writing the schemata file (on AMD systems)
--------------------------------------------------
-Reading the schemata file will show the state of all resources
-on all domains. When writing the memory bandwidth allocation you
-only need to specify those values in an absolute number expressed
-in 1/8 GB/s increments. To allocate bandwidth limit of 2GB, you
-need to specify the value 16 (16 * 1/8 = 2). For example:
+Reading the schemata file will show the current bandwidth limit on all
+domains. The allocated resources are in multiples of one eighth GB/s.
+When writing to the file, you need to specify what cache id you wish to
+configure the bandwidth limit.
+
+For example, to allocate 2GB/s limit on the first cache id:
+
::
# cat schemata
@@ -593,11 +596,11 @@ need to specify the value 16 (16 * 1/8 = 2). For example:
Reading/writing the schemata file (on AMD systems) with SMBA feature
--------------------------------------------------------------------
-Reading the schemata file will show the state of all resources
-on all domains. When writing the memory bandwidth allocation you
-only need to specify those values in an absolute number expressed
-in 1/8 GB/s increments. To allocate bandwidth limit of 8GB, you
-need to specify the value 64 (64 * 1/8 = 8). E.g.
+Reading and writing the schemata file is the same as without SMBA in
+above section.
+
+For example, to allocate 8GB/s limit on the first cache id:
+
::
# cat schemata
Thanks.
--
An old man doll... just what I always wanted! - Clara
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