| Message ID | 20240604020549.1017540-9-yuanchu@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | mm: workingset reporting | expand |
Hi, Just a couple of nits below: On 6/3/24 7:05 PM, Yuanchu Xie wrote: > Add workingset reporting documentation for better discoverability of > its sysfs and memcg interfaces. Also document the required kernel > config to enable workingset reporting. > > Signed-off-by: Yuanchu Xie <yuanchu@google.com> > --- > Documentation/admin-guide/mm/index.rst | 1 + > .../admin-guide/mm/workingset_report.rst | 105 ++++++++++++++++++ > 2 files changed, 106 insertions(+) > create mode 100644 Documentation/admin-guide/mm/workingset_report.rst > > diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst > index 1f883abf3f00..fba987de8997 100644 > --- a/Documentation/admin-guide/mm/index.rst > +++ b/Documentation/admin-guide/mm/index.rst > @@ -41,4 +41,5 @@ the Linux memory management. > swap_numa > transhuge > userfaultfd > + workingset_report > zswap > diff --git a/Documentation/admin-guide/mm/workingset_report.rst b/Documentation/admin-guide/mm/workingset_report.rst > new file mode 100644 > index 000000000000..f455ae93b30e > --- /dev/null > +++ b/Documentation/admin-guide/mm/workingset_report.rst > @@ -0,0 +1,105 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +================= > +Workingset Report > +================= > +Workingset report provides a view of memory coldness in user-defined > +time intervals, i.e. X bytes are Y milliseconds cold. It breaks down > +the user pages in the system per-NUMA node, per-memcg, for both > +anonymous and file pages into histograms that look like: > +:: > + > + 1000 anon=137368 file=24530 > + 20000 anon=34342 file=0 > + 30000 anon=353232 file=333608 > + 40000 anon=407198 file=206052 > + 9223372036854775807 anon=4925624 file=892892 > + > +The workingset reports can be used to drive proactive reclaim, by > +identifying the number of cold bytes in a memcg, then writing to > +``memory.reclaim``. > + > +Quick start > +=========== > +Build the kernel with the following configurations. The report relies > +on Multi-gen LRU for page coldness. > + > +* ``CONFIG_LRU_GEN=y`` > +* ``CONFIG_LRU_GEN_ENABLED=y`` > +* ``CONFIG_WORKINGSET_REPORT=y`` > + > +Optionally, the aging kernel daemon can be enabled with the following > +configuration. > +* ``CONFIG_LRU_GEN_ENABLED=y`` > + > +Sysfs interfaces > +================ > +``/sys/devices/system/node/nodeX/page_age`` provides a per-node page > +age histogram, showing an aggregate of the node's lruvecs. > +Reading this file causes a hierarchical aging of all lruvecs, scanning > +pages and creates a new Multi-gen LRU generation in each lruvec. > +For example: > +:: > + > + 1000 anon=0 file=0 > + 2000 anon=0 file=0 > + 100000 anon=5533696 file=5566464 > + 18446744073709551615 anon=0 file=0 > + > +``/sys/devices/system/node/nodeX/page_age_interval`` is a comma > +separated list of time in milliseconds that configures what the page > +age histogram uses for aggregation. For the above histogram, > +the intervals are: > +:: > + 1000,2000,100000 > + > +``/sys/devices/system/node/nodeX/workingset_report/refresh_interval`` > +defines the amount of time the report is valid for in milliseconds. > +When a report is still valid, reading the ``page_age`` file shows > +the existing valid report, instead of generating a new one. > + > +``/sys/devices/system/node/nodeX/workingset_report/report_threshold`` > +specifies how often the userspace agent can be notified for node > +memory pressure, in milliseconds. When a node reaches its low > +watermarks and wakes up kswapd, programs waiting on ``page_age`` are > +woken up so they can read the histogram and make policy decisions. > + > +Memcg interface > +=============== > +While ``page_age_interval`` is defined per-node in sysfs. ``page_age``, sysfs, > +``refresh_interval`` and ``report_threshold`` are available per-memcg. > + > +``/sys/fs/cgroup/.../memory.workingset.page_age`` > +The memcg equivalent of the sysfs workingset page age histogram, no comma ^ > +breaks down the workingset of this memcg and its children into > +page age intervals. Each node is prefixed with a node header and > +a newline. Non-proactive direct reclaim on this memcg can also > +wake up userspace agents that are waiting on this file. > +e.g. > +:: > + > + N0 > + 1000 anon=0 file=0 > + 2000 anon=0 file=0 > + 3000 anon=0 file=0 > + 4000 anon=0 file=0 > + 5000 anon=0 file=0 > + 18446744073709551615 anon=0 file=0 > + > +``/sys/fs/cgroup/.../memory.workingset.refresh_interval`` > +The memcg equivalent of the sysfs refresh interval. A per-node > +number of how much time a page age histogram is valid for, in > +milliseconds. > +e.g. > +:: > + > + echo N0=2000 > memory.workingset.refresh_interval > + > +``/sys/fs/cgroup/.../memory.workingset.report_threshold`` > +The memcg equivalent of the sysfs report threshold. A per-node > +number of how often userspace agent waiting on the page age > +histogram can be woken up, in milliseconds. > +e.g. > +:: > + > + echo N0=1000 > memory.workingset.report_threshold
diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst index 1f883abf3f00..fba987de8997 100644 --- a/Documentation/admin-guide/mm/index.rst +++ b/Documentation/admin-guide/mm/index.rst @@ -41,4 +41,5 @@ the Linux memory management. swap_numa transhuge userfaultfd + workingset_report zswap diff --git a/Documentation/admin-guide/mm/workingset_report.rst b/Documentation/admin-guide/mm/workingset_report.rst new file mode 100644 index 000000000000..f455ae93b30e --- /dev/null +++ b/Documentation/admin-guide/mm/workingset_report.rst @@ -0,0 +1,105 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================= +Workingset Report +================= +Workingset report provides a view of memory coldness in user-defined +time intervals, i.e. X bytes are Y milliseconds cold. It breaks down +the user pages in the system per-NUMA node, per-memcg, for both +anonymous and file pages into histograms that look like: +:: + + 1000 anon=137368 file=24530 + 20000 anon=34342 file=0 + 30000 anon=353232 file=333608 + 40000 anon=407198 file=206052 + 9223372036854775807 anon=4925624 file=892892 + +The workingset reports can be used to drive proactive reclaim, by +identifying the number of cold bytes in a memcg, then writing to +``memory.reclaim``. + +Quick start +=========== +Build the kernel with the following configurations. The report relies +on Multi-gen LRU for page coldness. + +* ``CONFIG_LRU_GEN=y`` +* ``CONFIG_LRU_GEN_ENABLED=y`` +* ``CONFIG_WORKINGSET_REPORT=y`` + +Optionally, the aging kernel daemon can be enabled with the following +configuration. +* ``CONFIG_LRU_GEN_ENABLED=y`` + +Sysfs interfaces +================ +``/sys/devices/system/node/nodeX/page_age`` provides a per-node page +age histogram, showing an aggregate of the node's lruvecs. +Reading this file causes a hierarchical aging of all lruvecs, scanning +pages and creates a new Multi-gen LRU generation in each lruvec. +For example: +:: + + 1000 anon=0 file=0 + 2000 anon=0 file=0 + 100000 anon=5533696 file=5566464 + 18446744073709551615 anon=0 file=0 + +``/sys/devices/system/node/nodeX/page_age_interval`` is a comma +separated list of time in milliseconds that configures what the page +age histogram uses for aggregation. For the above histogram, +the intervals are: +:: + 1000,2000,100000 + +``/sys/devices/system/node/nodeX/workingset_report/refresh_interval`` +defines the amount of time the report is valid for in milliseconds. +When a report is still valid, reading the ``page_age`` file shows +the existing valid report, instead of generating a new one. + +``/sys/devices/system/node/nodeX/workingset_report/report_threshold`` +specifies how often the userspace agent can be notified for node +memory pressure, in milliseconds. When a node reaches its low +watermarks and wakes up kswapd, programs waiting on ``page_age`` are +woken up so they can read the histogram and make policy decisions. + +Memcg interface +=============== +While ``page_age_interval`` is defined per-node in sysfs. ``page_age``, +``refresh_interval`` and ``report_threshold`` are available per-memcg. + +``/sys/fs/cgroup/.../memory.workingset.page_age`` +The memcg equivalent of the sysfs workingset page age histogram, +breaks down the workingset of this memcg and its children into +page age intervals. Each node is prefixed with a node header and +a newline. Non-proactive direct reclaim on this memcg can also +wake up userspace agents that are waiting on this file. +e.g. +:: + + N0 + 1000 anon=0 file=0 + 2000 anon=0 file=0 + 3000 anon=0 file=0 + 4000 anon=0 file=0 + 5000 anon=0 file=0 + 18446744073709551615 anon=0 file=0 + +``/sys/fs/cgroup/.../memory.workingset.refresh_interval`` +The memcg equivalent of the sysfs refresh interval. A per-node +number of how much time a page age histogram is valid for, in +milliseconds. +e.g. +:: + + echo N0=2000 > memory.workingset.refresh_interval + +``/sys/fs/cgroup/.../memory.workingset.report_threshold`` +The memcg equivalent of the sysfs report threshold. A per-node +number of how often userspace agent waiting on the page age +histogram can be woken up, in milliseconds. +e.g. +:: + + echo N0=1000 > memory.workingset.report_threshold
Add workingset reporting documentation for better discoverability of its sysfs and memcg interfaces. Also document the required kernel config to enable workingset reporting. Signed-off-by: Yuanchu Xie <yuanchu@google.com> --- Documentation/admin-guide/mm/index.rst | 1 + .../admin-guide/mm/workingset_report.rst | 105 ++++++++++++++++++ 2 files changed, 106 insertions(+) create mode 100644 Documentation/admin-guide/mm/workingset_report.rst