[PATCH 0/2] mm/damon: build-enable essential DAMON components by default

[PATCH 0/2] mm/damon: build-enable essential DAMON components by default

[SeongJae Park]

As of this writing, multiple major distros including Alma, Amazon,
Android, CentOS, Debian, Fedora, and Oracle are build-enabling DAMON
(set CONFIG_DAMON[1]).  Configuring DAMON is not very easy, since it is
disabled by default, and there are multiple essential options that need
to be manually turned on, one by one.  Make it easier, by grouping
essential configurations to be enabled with one selection, and enabling
build of the essential parts of DAMON by default.

Note that build-enabling DAMON does not introduce any real risk, since
it makes no behavioral change by default.  It requires explicit user
requests to do anything.  Only one potential risk is making the size of
the kernel a little bit larger.  On a production-purpose configuration,
it increases the resulting kernel package binary size by about 0.1 % of
the final package file.  I believe that's too small to be a real problem
in common setups.

Changes from RFC
(https://lore.kernel.org/20250512182716.50245-1-sj@kernel.org)
- Rebase to latest mm-new
- Wordsmith cover letter and commit messages

[1] https://oracle.github.io/kconfigs/?config=UTS_RELEASE&config=DAMON

SeongJae Park (2):
  mm/damon/Kconfig: set DAMON_{VADDR,PADDR,SYSFS} default to DAMON
  mm/damon/Kconfig: enable CONFIG_DAMON by default

 mm/damon/Kconfig | 4 ++++
 1 file changed, 4 insertions(+)


base-commit: 88d53b68fa80a693259ba705b4750f91e9c77888
-- 
2.39.5

[PATCH 1/2] mm/damon/Kconfig: set DAMON_{VADDR,PADDR,SYSFS} default to DAMON

[SeongJae Park]

DAMON_{VADDR,PADDR,SYSFS} are de-facto essential parts of DAMON for
normal usages.  Because those need to be enabled one by one, however,
and there are other test-purpose or non-essential configurations, it is
easy to be confused and make mistakes at setup.  Make the essential
configurations default to CONFIG_DAMON, so that those can be enabled by
default with a single change.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/Kconfig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index c213cf8b5638..c93d0c56b963 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -28,6 +28,7 @@ config DAMON_VADDR
 	bool "Data access monitoring operations for virtual address spaces"
 	depends on DAMON && MMU
 	select PAGE_IDLE_FLAG
+	default DAMON
 	help
 	  This builds the default data access monitoring operations for DAMON
 	  that work for virtual address spaces.
@@ -36,6 +37,7 @@ config DAMON_PADDR
 	bool "Data access monitoring operations for the physical address space"
 	depends on DAMON && MMU
 	select PAGE_IDLE_FLAG
+	default DAMON
 	help
 	  This builds the default data access monitoring operations for DAMON
 	  that works for the physical address space.
@@ -55,6 +57,7 @@ config DAMON_VADDR_KUNIT_TEST
 config DAMON_SYSFS
 	bool "DAMON sysfs interface"
 	depends on DAMON && SYSFS
+	default DAMON
 	help
 	  This builds the sysfs interface for DAMON.  The user space can use
 	  the interface for arbitrary data access monitoring.
-- 
2.39.5

Re: [PATCH 1/2] mm/damon/Kconfig: set DAMON_{VADDR,PADDR,SYSFS} default to DAMON

[Honggyu Kim]

Hi SeongJae,

This is the patch I was waiting for.  Since enabling DAMON build doesn't
directly impact the kernel behaviors as it is disabled by default.

On 5/21/2025 1:27 PM, SeongJae Park wrote:
> DAMON_{VADDR,PADDR,SYSFS} are de-facto essential parts of DAMON for
> normal usages.  Because those need to be enabled one by one, however,
> and there are other test-purpose or non-essential configurations, it is
> easy to be confused and make mistakes at setup.  Make the essential
> configurations default to CONFIG_DAMON, so that those can be enabled by
> default with a single change.
> 
> Signed-off-by: SeongJae Park <sj@kernel.org>
> ---
>   mm/damon/Kconfig | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
> index c213cf8b5638..c93d0c56b963 100644
> --- a/mm/damon/Kconfig
> +++ b/mm/damon/Kconfig
> @@ -28,6 +28,7 @@ config DAMON_VADDR
>   	bool "Data access monitoring operations for virtual address spaces"
>   	depends on DAMON && MMU
>   	select PAGE_IDLE_FLAG
> +	default DAMON
>   	help
>   	  This builds the default data access monitoring operations for DAMON
>   	  that work for virtual address spaces.
> @@ -36,6 +37,7 @@ config DAMON_PADDR
>   	bool "Data access monitoring operations for the physical address space"
>   	depends on DAMON && MMU
>   	select PAGE_IDLE_FLAG
> +	default DAMON
>   	help
>   	  This builds the default data access monitoring operations for DAMON
>   	  that works for the physical address space.
> @@ -55,6 +57,7 @@ config DAMON_VADDR_KUNIT_TEST
>   config DAMON_SYSFS
>   	bool "DAMON sysfs interface"
>   	depends on DAMON && SYSFS
> +	default DAMON
>   	help
>   	  This builds the sysfs interface for DAMON.  The user space can use
>   	  the interface for arbitrary data access monitoring.

I'm not sure if I'm elighble to ack your patch, but I would like to add

	Acked-by: Honggyu Kim <honggyu.kim@sk.com>

Thanks,
Honggyu

Re: [PATCH 1/2] mm/damon/Kconfig: set DAMON_{VADDR,PADDR,SYSFS} default to DAMON

[SeongJae Park]

On Thu, 22 May 2025 14:54:33 +0900 Honggyu Kim <honggyu.kim@sk.com> wrote:

> Hi SeongJae,
> 
> This is the patch I was waiting for.

I'm more than glad to hear this :)  Also appreciate/apology for your wait.

[...]
> I'm not sure if I'm elighble to ack your patch, but

I pretty sure you're eligible.

> I would like to add
> 
> 	Acked-by: Honggyu Kim <honggyu.kim@sk.com>

Thank you, this means a lot to me!


Thanks,
SJ

[...]

[PATCH 2/2] mm/damon/Kconfig: enable CONFIG_DAMON by default

[SeongJae Park]

As of this writing, multiple major distros including Alma, Amazon,
Android, CentOS, Debian, Fedora, and Oracle are build-enabling DAMON
(set CONFIG_DAMON[1]).  Enabling it by default will save configuration
setup time for the current and future DAMON users.

Build-enabling DAMON does not introduce a real risk since it makes no
behavioral change by default.  It requires explicit user requests to do
anything.  Only one potential risk is making the size of the kernel a
little bit larger.  On a production-purpose configuration, it increases
the resulting kernel package size by about 0.1 % of the final package
file.  I believe that's too small to be a real problem in common setups.

Hence, the benefit of enabling CONFIG_DAMON outweighs the potential
risk.  Set CONFIG_DAMON by default.

[1] https://oracle.github.io/kconfigs/?config=UTS_RELEASE&config=DAMON

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
index c93d0c56b963..551745df011b 100644
--- a/mm/damon/Kconfig
+++ b/mm/damon/Kconfig
@@ -4,6 +4,7 @@ menu "Data Access Monitoring"
 
 config DAMON
 	bool "DAMON: Data Access Monitoring Framework"
+	default y
 	help
 	  This builds a framework that allows kernel subsystems to monitor
 	  access frequency of each memory region. The information can be useful
-- 
2.39.5

Re: [PATCH 2/2] mm/damon/Kconfig: enable CONFIG_DAMON by default

[Honggyu Kim]

On 5/21/2025 1:27 PM, SeongJae Park wrote:
> As of this writing, multiple major distros including Alma, Amazon,
> Android, CentOS, Debian, Fedora, and Oracle are build-enabling DAMON
> (set CONFIG_DAMON[1]).  Enabling it by default will save configuration
> setup time for the current and future DAMON users.
> 
> Build-enabling DAMON does not introduce a real risk since it makes no
> behavioral change by default.  It requires explicit user requests to do
> anything.  Only one potential risk is making the size of the kernel a
> little bit larger.  On a production-purpose configuration, it increases
> the resulting kernel package size by about 0.1 % of the final package
> file.  I believe that's too small to be a real problem in common setups.
> 
> Hence, the benefit of enabling CONFIG_DAMON outweighs the potential
> risk.  Set CONFIG_DAMON by default.

Agreed.

> [1] https://oracle.github.io/kconfigs/?config=UTS_RELEASE&config=DAMON
> 
> Signed-off-by: SeongJae Park <sj@kernel.org>
> ---
>   mm/damon/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/mm/damon/Kconfig b/mm/damon/Kconfig
> index c93d0c56b963..551745df011b 100644
> --- a/mm/damon/Kconfig
> +++ b/mm/damon/Kconfig
> @@ -4,6 +4,7 @@ menu "Data Access Monitoring"
>   
>   config DAMON
>   	bool "DAMON: Data Access Monitoring Framework"
> +	default y
>   	help
>   	  This builds a framework that allows kernel subsystems to monitor
>   	  access frequency of each memory region. The information can be useful

     Acked-by: Honggyu Kim <honggyu.kim@sk.com>

Thanks,
Honggyu