€• 3      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ-/translations/zh_CN/admin-guide/mm/damon/stat”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/zh_TW/admin-guide/mm/damon/stat”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/it_IT/admin-guide/mm/damon/stat”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/ja_JP/admin-guide/mm/damon/stat”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/ko_KR/admin-guide/mm/damon/stat”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/sp_SP/admin-guide/mm/damon/stat”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒG/var/lib/git/docbuild/linux/Documentation/admin-guide/mm/damon/stat.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ#Data Access Monitoring Results Stat”h]”hŒ#Data Access Monitoring Results Stat”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h KubhŒ	paragraph”“”)”}”(hXN  Data Access Monitoring Results Stat (DAMON_STAT) is a static kernel module that
is aimed to be used for simple access pattern monitoring.  It monitors accesses
on the system's entire physical memory using DAMON, and provides simplified
access monitoring results statistics, namely idle time percentiles and
estimated memory bandwidth.”h]”hXP  Data Access Monitoring Results Stat (DAMON_STAT) is a static kernel module that
is aimed to be used for simple access pattern monitoring.  It monitors accesses
on the systemâ€™s entire physical memory using DAMON, and provides simplified
access monitoring results statistics, namely idle time percentiles and
estimated memory bandwidth.”…””}”(hhËhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhµ)”}”(hhh]”(hº)”}”(hŒ Monitoring Accuracy and Overhead”h]”hŒ Monitoring Accuracy and Overhead”…””}”(hhÜhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÙhžhhŸh³h KubhÊ)”}”(hXô  DAMON_STAT uses monitoring intervals :ref:`auto-tuning
<damon_design_monitoring_intervals_autotuning>` to make its accuracy high and
overhead minimum.  It auto-tunes the intervals aiming 4 % of observable access
events to be captured in each snapshot, while limiting the resulting sampling
events to be 5 milliseconds in minimum and 10 seconds in maximum.  On a few
production server systems, it resulted in consuming only 0.x % single CPU time,
while capturing reasonable quality of access patterns.”h]”(hŒ%DAMON_STAT uses monitoring intervals ”…””}”(hhêhžhhŸNh Nubh)”}”(hŒA:ref:`auto-tuning
<damon_design_monitoring_intervals_autotuning>`”h]”hŒinline”“”)”}”(hhôh]”hŒauto-tuning”…””}”(hhøhžhhŸNh Nubah}”(h]”h ]”(Œxref”Œstd”Œstd-ref”eh"]”h$]”h&]”uh1höhhòubah}”(h]”h ]”h"]”h$]”h&]”Œrefdoc”Œadmin-guide/mm/damon/stat”Œ	refdomain”j  Œreftype”Œref”Œrefexplicit”ˆŒrefwarn”ˆŒ	reftarget”Œ,damon_design_monitoring_intervals_autotuning”uh1hhŸh³h KhhêubhXŽ   to make its accuracy high and
overhead minimum.  It auto-tunes the intervals aiming 4 % of observable access
events to be captured in each snapshot, while limiting the resulting sampling
events to be 5 milliseconds in minimum and 10 seconds in maximum.  On a few
production server systems, it resulted in consuming only 0.x % single CPU time,
while capturing reasonable quality of access patterns.”…””}”(hhêhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KhhÙhžhubeh}”(h]”Œ monitoring-accuracy-and-overhead”ah ]”h"]”Œ monitoring accuracy and overhead”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒInterface: Module Parameters”h]”hŒInterface: Module Parameters”…””}”(hj,  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj)  hžhhŸh³h KubhÊ)”}”(hŒèTo use this feature, you should first ensure your system is running on a kernel
that is built with ``CONFIG_DAMON_STAT=y``.  The feature can be enabled by
default at build time, by setting ``CONFIG_DAMON_STAT_ENABLED_DEFAULT`` true.”h]”(hŒcTo use this feature, you should first ensure your system is running on a kernel
that is built with ”…””}”(hj:  hžhhŸNh NubhŒliteral”“”)”}”(hŒ``CONFIG_DAMON_STAT=y``”h]”hŒCONFIG_DAMON_STAT=y”…””}”(hjD  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jB  hj:  ubhŒC.  The feature can be enabled by
default at build time, by setting ”…””}”(hj:  hžhhŸNh NubjC  )”}”(hŒ%``CONFIG_DAMON_STAT_ENABLED_DEFAULT``”h]”hŒ!CONFIG_DAMON_STAT_ENABLED_DEFAULT”…””}”(hjV  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jB  hj:  ubhŒ true.”…””}”(hj:  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj)  hžhubhÊ)”}”(hŒ½To let sysadmins enable or disable it at boot and/or runtime, and read the
monitoring results, DAMON_STAT provides module parameters.  Following
sections are descriptions of the parameters.”h]”hŒ½To let sysadmins enable or disable it at boot and/or runtime, and read the
monitoring results, DAMON_STAT provides module parameters.  Following
sections are descriptions of the parameters.”…””}”(hjn  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj)  hžhubhµ)”}”(hhh]”(hº)”}”(hŒenabled”h]”hŒenabled”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj|  hžhhŸh³h K$ubhÊ)”}”(hŒEnable or disable DAMON_STAT.”h]”hŒEnable or disable DAMON_STAT.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K&hj|  hžhubhÊ)”}”(hŒËYou can enable DAMON_STAT by setting the value of this parameter as ``Y``.
Setting it as ``N`` disables DAMON_STAT.  The default value is set by
``CONFIG_DAMON_STAT_ENABLED_DEFAULT`` build config option.”h]”(hŒDYou can enable DAMON_STAT by setting the value of this parameter as ”…””}”(hj›  hžhhŸNh NubjC  )”}”(hŒ``Y``”h]”hŒY”…””}”(hj£  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jB  hj›  ubhŒ.
Setting it as ”…””}”(hj›  hžhhŸNh NubjC  )”}”(hŒ``N``”h]”hŒN”…””}”(hjµ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jB  hj›  ubhŒ3 disables DAMON_STAT.  The default value is set by
”…””}”(hj›  hžhhŸNh NubjC  )”}”(hŒ%``CONFIG_DAMON_STAT_ENABLED_DEFAULT``”h]”hŒ!CONFIG_DAMON_STAT_ENABLED_DEFAULT”…””}”(hjÇ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jB  hj›  ubhŒ build config option.”…””}”(hj›  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K(hj|  hžhubeh}”(h]”Œenabled”ah ]”h"]”Œenabled”ah$]”h&]”uh1h´hj)  hžhhŸh³h K$ubhµ)”}”(hhh]”(hº)”}”(hŒestimated_memory_bandwidth”h]”hŒestimated_memory_bandwidth”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjç  hžhhŸh³h K-ubhÊ)”}”(hŒHEstimated memory bandwidth consumption (bytes per second) of the system.”h]”hŒHEstimated memory bandwidth consumption (bytes per second) of the system.”…””}”(hjø  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K/hjç  hžhubhÊ)”}”(hX[  DAMON_STAT reads observed access events on the current DAMON results snapshot
and converts it to memory bandwidth consumption estimation in bytes per second.
The resulting metric is exposed to user via this read-only parameter.  Because
DAMON uses sampling, this is only an estimation of the access intensity rather
than accurate memory bandwidth.”h]”hX[  DAMON_STAT reads observed access events on the current DAMON results snapshot
and converts it to memory bandwidth consumption estimation in bytes per second.
The resulting metric is exposed to user via this read-only parameter.  Because
DAMON uses sampling, this is only an estimation of the access intensity rather
than accurate memory bandwidth.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K1hjç  hžhubeh}”(h]”Œestimated-memory-bandwidth”ah ]”h"]”Œestimated_memory_bandwidth”ah$]”h&]”uh1h´hj)  hžhhŸh³h K-ubhµ)”}”(hhh]”(hº)”}”(hŒmemory_idle_ms_percentiles”h]”hŒmemory_idle_ms_percentiles”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj  hžhhŸh³h K8ubhÊ)”}”(hŒ<Per-byte idle time (milliseconds) percentiles of the system.”h]”hŒ<Per-byte idle time (milliseconds) percentiles of the system.”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K:hj  hžhubhÊ)”}”(hX¾  DAMON_STAT calculates how long each byte of the memory was not accessed until
now (idle time), based on the current DAMON results snapshot.  If DAMON found a
region of access frequency (nr_accesses) larger than zero, every byte of the
region gets zero idle time.  If a region has zero access frequency
(nr_accesses), how long the region was keeping the zero access frequency (age)
becomes the idle time of every byte of the region.  Then, DAMON_STAT exposes
the percentiles of the idle time values via this read-only parameter.  Reading
the parameter returns 101 idle time values in milliseconds, separated by comma.
Each value represents 0-th, 1st, 2nd, 3rd, ..., 99th and 100th percentile idle
times.”h]”hX¾  DAMON_STAT calculates how long each byte of the memory was not accessed until
now (idle time), based on the current DAMON results snapshot.  If DAMON found a
region of access frequency (nr_accesses) larger than zero, every byte of the
region gets zero idle time.  If a region has zero access frequency
(nr_accesses), how long the region was keeping the zero access frequency (age)
becomes the idle time of every byte of the region.  Then, DAMON_STAT exposes
the percentiles of the idle time values via this read-only parameter.  Reading
the parameter returns 101 idle time values in milliseconds, separated by comma.
Each value represents 0-th, 1st, 2nd, 3rd, ..., 99th and 100th percentile idle
times.”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K<hj  hžhubeh}”(h]”Œmemory-idle-ms-percentiles”ah ]”h"]”Œmemory_idle_ms_percentiles”ah$]”h&]”uh1h´hj)  hžhhŸh³h K8ubeh}”(h]”Œinterface-module-parameters”ah ]”h"]”Œinterface: module parameters”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubeh}”(h]”Œ#data-access-monitoring-results-stat”ah ]”h"]”Œ#data access monitoring results stat”ah$]”h&]”uh1h´hhhžhhŸh³h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
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