Commit 059342d1dd ("mm/damon/reclaim: fix the timer always stays
active") made DAMON_RECLAIM's 'enabled' parameter store callback,
'enabled_store()', to schedule 'damon_reclaim_timer'. The scheduling uses
'system_wq', which is initialized in 'workqueue_init_early()'. As kernel
parameters parsing function ('parse_args()') is called before
'workqueue_init_early()', 'enabled_store()' can be executed before
'workqueue_init_early()' and end up accessing the uninitialized
'system_wq'. As a result, the booting hang[1]. This commit fixes the
issue by checking if the initialization is done before scheduling the
timer.
[1] https://lkml.kernel.org/20220604192222.1488-1-sj@kernel.org/
Link: https://lkml.kernel.org/r/20220604195051.1589-1-sj@kernel.org
Fixes: 059342d1dd ("mm/damon/reclaim: fix the timer always stays active")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Greg White <gwhite@kupulau.com>
Cc: Hailong Tu <tuhailong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
DAMON_RECLAIM reads the user input parameters only when it starts. To
allow more efficient online tuning, this commit implements a new input
parameter called 'commit_inputs'. Writing true to the parameter makes
DAMON_RECLAIM reads the input parameters again.
Link: https://lkml.kernel.org/r/20220429160606.127307-14-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The timer stays active even if the reclaim mechanism is never enabled. It
is unnecessary overhead can be completely avoided by using
module_param_cb() for enabled flag.
Link: https://lkml.kernel.org/r/20220421125910.1052459-1-tuhailong@gmail.com
Signed-off-by: Hailong Tu <tuhailong@gmail.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Introduce DAMON sysfs interface", v3.
Introduction
============
DAMON's debugfs-based user interface (DAMON_DBGFS) served very well, so
far. However, it unnecessarily depends on debugfs, while DAMON is not
aimed to be used for only debugging. Also, the interface receives
multiple values via one file. For example, schemes file receives 18
values. As a result, it is inefficient, hard to be used, and difficult to
be extended. Especially, keeping backward compatibility of user space
tools is getting only challenging. It would be better to implement
another reliable and flexible interface and deprecate DAMON_DBGFS in long
term.
For the reason, this patchset introduces a sysfs-based new user interface
of DAMON. The idea of the new interface is, using directory hierarchies
and having one dedicated file for each value. For a short example, users
can do the virtual address monitoring via the interface as below:
# cd /sys/kernel/mm/damon/admin/
# echo 1 > kdamonds/nr_kdamonds
# echo 1 > kdamonds/0/contexts/nr_contexts
# echo vaddr > kdamonds/0/contexts/0/operations
# echo 1 > kdamonds/0/contexts/0/targets/nr_targets
# echo $(pidof <workload>) > kdamonds/0/contexts/0/targets/0/pid_target
# echo on > kdamonds/0/state
A brief representation of the files hierarchy of DAMON sysfs interface is
as below. Childs are represented with indentation, directories are having
'/' suffix, and files in each directory are separated by comma.
/sys/kernel/mm/damon/admin
│ kdamonds/nr_kdamonds
│ │ 0/state,pid
│ │ │ contexts/nr_contexts
│ │ │ │ 0/operations
│ │ │ │ │ monitoring_attrs/
│ │ │ │ │ │ intervals/sample_us,aggr_us,update_us
│ │ │ │ │ │ nr_regions/min,max
│ │ │ │ │ targets/nr_targets
│ │ │ │ │ │ 0/pid_target
│ │ │ │ │ │ │ regions/nr_regions
│ │ │ │ │ │ │ │ 0/start,end
│ │ │ │ │ │ │ │ ...
│ │ │ │ │ │ ...
│ │ │ │ │ schemes/nr_schemes
│ │ │ │ │ │ 0/action
│ │ │ │ │ │ │ access_pattern/
│ │ │ │ │ │ │ │ sz/min,max
│ │ │ │ │ │ │ │ nr_accesses/min,max
│ │ │ │ │ │ │ │ age/min,max
│ │ │ │ │ │ │ quotas/ms,bytes,reset_interval_ms
│ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
│ │ │ │ │ │ │ watermarks/metric,interval_us,high,mid,low
│ │ │ │ │ │ │ stats/nr_tried,sz_tried,nr_applied,sz_applied,qt_exceeds
│ │ │ │ │ │ ...
│ │ │ │ ...
│ │ ...
Detailed usage of the files will be described in the final Documentation
patch of this patchset.
Main Difference Between DAMON_DBGFS and DAMON_SYSFS
---------------------------------------------------
At the moment, DAMON_DBGFS and DAMON_SYSFS provides same features. One
important difference between them is their exclusiveness. DAMON_DBGFS
works in an exclusive manner, so that no DAMON worker thread (kdamond) in
the system can run concurrently and interfere somehow. For the reason,
DAMON_DBGFS asks users to construct all monitoring contexts and start them
at once. It's not a big problem but makes the operation a little bit
complex and unflexible.
For more flexible usage, DAMON_SYSFS moves the responsibility of
preventing any possible interference to the admins and work in a
non-exclusive manner. That is, users can configure and start contexts one
by one. Note that DAMON respects both exclusive groups and non-exclusive
groups of contexts, in a manner similar to that of reader-writer locks.
That is, if any exclusive monitoring contexts (e.g., contexts that started
via DAMON_DBGFS) are running, DAMON_SYSFS does not start new contexts, and
vice versa.
Future Plan of DAMON_DBGFS Deprecation
======================================
Once this patchset is merged, DAMON_DBGFS development will be frozen.
That is, we will maintain it to work as is now so that no users will be
break. But, it will not be extended to provide any new feature of DAMON.
The support will be continued only until next LTS release. After that, we
will drop DAMON_DBGFS.
User-space Tooling Compatibility
--------------------------------
As DAMON_SYSFS provides all features of DAMON_DBGFS, all user space
tooling can move to DAMON_SYSFS. As we will continue supporting
DAMON_DBGFS until next LTS kernel release, user space tools would have
enough time to move to DAMON_SYSFS.
The official user space tool, damo[1], is already supporting both
DAMON_SYSFS and DAMON_DBGFS. Both correctness tests[2] and performance
tests[3] of DAMON using DAMON_SYSFS also passed.
[1] https://github.com/awslabs/damo
[2] https://github.com/awslabs/damon-tests/tree/master/corr
[3] https://github.com/awslabs/damon-tests/tree/master/perf
Sequence of Patches
===================
First two patches (patches 1-2) make core changes for DAMON_SYSFS. The
first one (patch 1) allows non-exclusive DAMON contexts so that
DAMON_SYSFS can work in non-exclusive mode, while the second one (patch 2)
adds size of DAMON enum types so that DAMON API users can safely iterate
the enums.
Third patch (patch 3) implements basic sysfs stub for virtual address
spaces monitoring. Note that this implements only sysfs files and DAMON
is not linked. Fourth patch (patch 4) links the DAMON_SYSFS to DAMON so
that users can control DAMON using the sysfs files.
Following six patches (patches 5-10) implements other DAMON features that
DAMON_DBGFS supports one by one (physical address space monitoring,
DAMON-based operation schemes, schemes quotas, schemes prioritization
weights, schemes watermarks, and schemes stats).
Following patch (patch 11) adds a simple selftest for DAMON_SYSFS, and the
final one (patch 12) documents DAMON_SYSFS.
This patch (of 13):
To avoid interference between DAMON contexts monitoring overlapping memory
regions, damon_start() works in an exclusive manner. That is,
damon_start() does nothing bug fails if any context that started by
another instance of the function is still running. This makes its usage a
little bit restrictive. However, admins could aware each DAMON usage and
address such interferences on their own in some cases.
This commit hence implements non-exclusive mode of the function and allows
the callers to select the mode. Note that the exclusive groups and
non-exclusive groups of contexts will respect each other in a manner
similar to that of reader-writer locks. Therefore, this commit will not
cause any behavioral change to the exclusive groups.
Link: https://lkml.kernel.org/r/20220228081314.5770-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220228081314.5770-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit makes DAMON_RECLAIM to select the registered monitoring
operations for the physical address space instead of setting it on its
own. This allows DAMON_RECLAIM be independent of DAMON_PADDR, but leave
the dependency as is, because it's the only one monitoring operations it
use, and therefore it makes no sense to build DAMON_RECLAIM without
DAMON_PADDR.
Link: https://lkml.kernel.org/r/20220215184603.1479-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Allow DAMON user code independent of monitoring primitives".
In-kernel DAMON user code is required to configure the monitoring context
(struct damon_ctx) with proper monitoring primitives (struct
damon_primitive). This makes the user code dependent to all supporting
monitoring primitives. For example, DAMON debugfs interface depends on
both DAMON_VADDR and DAMON_PADDR, though some users have interest in only
one use case. As more monitoring primitives are introduced, the problem
will be bigger.
To minimize such unnecessary dependency, this patchset makes monitoring
primitives can be registered by the implemnting code and later dynamically
searched and selected by the user code.
In addition to that, this patchset renames monitoring primitives to
monitoring operations, which is more easy to intuitively understand what
it means and how it would be structed.
This patch (of 8):
DAMON has a set of callback functions called monitoring primitives and let
it can be configured with various implementations for easy extension for
different address spaces and usages. However, the word 'primitive' is not
so explicit. Meanwhile, many other structs resembles similar purpose
calls themselves 'operations'. To make the code easier to be understood,
this commit renames 'damon_primitives' to 'damon_operations' before it is
too late to rename.
Link: https://lkml.kernel.org/r/20220215184603.1479-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20220215184603.1479-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DAMON asks each monitoring target ('struct damon_target') to have one
'unsigned long' integer called 'id', which should be unique among the
targets of same monitoring context. Meaning of it is, however, totally up
to the monitoring primitives that registered to the monitoring context.
For example, the virtual address spaces monitoring primitives treats the
id as a 'struct pid' pointer.
This makes the code flexible, but ugly, not well-documented, and
type-unsafe[1]. Also, identification of each target can be done via its
index. For the reason, this commit removes the concept and uses clear
type definition. For now, only 'struct pid' pointer is used for the
virtual address spaces monitoring. If DAMON is extended in future so that
we need to put another identifier field in the struct, we will use a union
for such primitives-dependent fields and document which primitives are
using which type.
[1] https://lore.kernel.org/linux-mm/20211013154535.4aaeaaf9d0182922e405dd1e@linux-foundation.org/
Link: https://lkml.kernel.org/r/20211230100723.2238-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This implements new DAMON_RECLAIM parameters for statistics reporting.
Those can be used for understanding how DAMON_RECLAIM is working, and
for tuning the other parameters.
Link: https://lkml.kernel.org/r/20211210150016.35349-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This implements a new kernel subsystem that finds cold memory regions
using DAMON and reclaims those immediately. It is intended to be used
as proactive lightweigh reclamation logic for light memory pressure.
For heavy memory pressure, it could be inactivated and fall back to the
traditional page-scanning based reclamation.
It's implemented on top of DAMON framework to use the DAMON-based
Operation Schemes (DAMOS) feature. It utilizes all the DAMOS features
including speed limit, prioritization, and watermarks.
It could be enabled and tuned in boot time via the kernel boot
parameter, and in run time via its module parameters
('/sys/module/damon_reclaim/parameters/') interface.
[yangyingliang@huawei.com: fix error return code in damon_reclaim_turn()]
Link: https://lkml.kernel.org/r/20211025124500.2758060-1-yangyingliang@huawei.com
Link: https://lkml.kernel.org/r/20211019150731.16699-15-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park