swapaccount= commandline option

swapaccount= commandline option

[Narcis Garcia]

Hello,

I read this warning on Linux 6.1 boot:
The swapaccount= commandline option is deprecated. Please report your 
usecase to linux-mm@kvack.org if you depend on this functionality.

And I want to know if this impacts on LinuX Containers (LXC) swap 
accounting.

Thank you.

-- 

Narcis Garcia

__________
I'm using this dedicated address because personal addresses aren't 
masked enough at this mail public archive. Public archive administrator 
should remove and omit any @, dot and mailto combinations against 
automated addresses collectors.

Re: swapaccount= commandline option

[Yosry Ahmed]

On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
>
> Hello,
>
> I read this warning on Linux 6.1 boot:
> The swapaccount= commandline option is deprecated. Please report your
> usecase to linux-mm@kvack.org if you depend on this functionality.
>
> And I want to know if this impacts on LinuX Containers (LXC) swap
> accounting.

swapaccount= was deprecated in the sense that it is always on now
(i.e. you cannot do swapaccount=0 anymore). I believe you are using
swapaccount=1 and want to make sure that swap accounting will still
work with v6.1, right?

This is the second question we have had about this message [1]. I
think we need to clarify the warning (and perhaps backport to stable
kernels).

[1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/

Re: swapaccount= commandline option

[Narcis Garcia]

El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
>>
>> Hello,
>>
>> I read this warning on Linux 6.1 boot:
>> The swapaccount= commandline option is deprecated. Please report your
>> usecase to linux-mm@kvack.org if you depend on this functionality.
>>
>> And I want to know if this impacts on LinuX Containers (LXC) swap
>> accounting.
> 
> swapaccount= was deprecated in the sense that it is always on now
> (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> swapaccount=1 and want to make sure that swap accounting will still
> work with v6.1, right?
> 
> This is the second question we have had about this message [1]. I
> think we need to clarify the warning (and perhaps backport to stable
> kernels).
> 
> [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/


Thank you for answering this question, and sure this clarification is 
needed both in documentation and warning message.
I've found deprecation message was commited on 26 Sep 2022.
 From what Linux version release, this deprecation is included?

I suggest this for setup_swap_account() code:
pr_warn_once("The swapaccount= commandline option is deprecated. "
	"Swap accounting is always on. "
	"Please report your usecase to linux-mm@kvack.org if you "
	"depend on this functionality.\n");

-- 

Narcis Garcia

__________
I'm using this dedicated address because personal addresses aren't 
masked enough at this mail public archive. Public archive administrator 
should remove and omit any @, dot and mailto combinations against 
automated addresses collectors.

Re: swapaccount= commandline option

[Yosry Ahmed]

On Mon, Feb 12, 2024 at 11:02 PM Narcis Garcia <debianlists@actiu.net> wrote:
>
> El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> >>
> >> Hello,
> >>
> >> I read this warning on Linux 6.1 boot:
> >> The swapaccount= commandline option is deprecated. Please report your
> >> usecase to linux-mm@kvack.org if you depend on this functionality.
> >>
> >> And I want to know if this impacts on LinuX Containers (LXC) swap
> >> accounting.
> >
> > swapaccount= was deprecated in the sense that it is always on now
> > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > swapaccount=1 and want to make sure that swap accounting will still
> > work with v6.1, right?
> >
> > This is the second question we have had about this message [1]. I
> > think we need to clarify the warning (and perhaps backport to stable
> > kernels).
> >
> > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
>
>
> Thank you for answering this question, and sure this clarification is
> needed both in documentation and warning message.
> I've found deprecation message was commited on 26 Sep 2022.
>  From what Linux version release, this deprecation is included?

I think v6.1 is the first kernel with the deprecation.

>
> I suggest this for setup_swap_account() code:
> pr_warn_once("The swapaccount= commandline option is deprecated. "
>         "Swap accounting is always on. "
>         "Please report your usecase to linux-mm@kvack.org if you "
>         "depend on this functionality.\n");

Sure. Would you like to send a patch or would you like me to take care of it?

Re: swapaccount= commandline option

[Michal Hocko]

On Tue 13-02-24 08:01:37, Narcis Garcia wrote:
> El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> > > 
> > > Hello,
> > > 
> > > I read this warning on Linux 6.1 boot:
> > > The swapaccount= commandline option is deprecated. Please report your
> > > usecase to linux-mm@kvack.org if you depend on this functionality.
> > > 
> > > And I want to know if this impacts on LinuX Containers (LXC) swap
> > > accounting.
> > 
> > swapaccount= was deprecated in the sense that it is always on now
> > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > swapaccount=1 and want to make sure that swap accounting will still
> > work with v6.1, right?
> > 
> > This is the second question we have had about this message [1]. I
> > think we need to clarify the warning (and perhaps backport to stable
> > kernels).
> > 
> > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
> 
> 
> Thank you for answering this question, and sure this clarification is needed
> both in documentation and warning message.
> I've found deprecation message was commited on 26 Sep 2022.
> From what Linux version release, this deprecation is included?
> 
> I suggest this for setup_swap_account() code:
> pr_warn_once("The swapaccount= commandline option is deprecated. "
> 	"Swap accounting is always on. "
> 	"Please report your usecase to linux-mm@kvack.org if you "
> 	"depend on this functionality.\n");

Would it make more sense to warn only if somebody tries to disable the
swap accounting?
--- 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e4c8735e7c85..dec75eedf634 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7936,7 +7936,10 @@ bool mem_cgroup_swap_full(struct folio *folio)
 
 static int __init setup_swap_account(char *s)
 {
-	pr_warn_once("The swapaccount= commandline option is deprecated. "
+	bool res;
+
+	if (kstrtobool(s, &res) || !res)
+		pr_warn_once("The swapaccount= commandline option is deprecated. "
 		     "Please report your usecase to linux-mm@kvack.org if you "
 		     "depend on this functionality.\n");
 	return 1;
-- 
Michal Hocko
SUSE Labs

Re: swapaccount= commandline option

[Yosry Ahmed]

On Tue, Feb 13, 2024 at 12:06 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Tue 13-02-24 08:01:37, Narcis Garcia wrote:
> > El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> > > >
> > > > Hello,
> > > >
> > > > I read this warning on Linux 6.1 boot:
> > > > The swapaccount= commandline option is deprecated. Please report your
> > > > usecase to linux-mm@kvack.org if you depend on this functionality.
> > > >
> > > > And I want to know if this impacts on LinuX Containers (LXC) swap
> > > > accounting.
> > >
> > > swapaccount= was deprecated in the sense that it is always on now
> > > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > > swapaccount=1 and want to make sure that swap accounting will still
> > > work with v6.1, right?
> > >
> > > This is the second question we have had about this message [1]. I
> > > think we need to clarify the warning (and perhaps backport to stable
> > > kernels).
> > >
> > > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
> >
> >
> > Thank you for answering this question, and sure this clarification is needed
> > both in documentation and warning message.
> > I've found deprecation message was commited on 26 Sep 2022.
> > From what Linux version release, this deprecation is included?
> >
> > I suggest this for setup_swap_account() code:
> > pr_warn_once("The swapaccount= commandline option is deprecated. "
> >       "Swap accounting is always on. "
> >       "Please report your usecase to linux-mm@kvack.org if you "
> >       "depend on this functionality.\n");
>
> Would it make more sense to warn only if somebody tries to disable the
> swap accounting?
> ---
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e4c8735e7c85..dec75eedf634 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7936,7 +7936,10 @@ bool mem_cgroup_swap_full(struct folio *folio)
>
>  static int __init setup_swap_account(char *s)
>  {
> -       pr_warn_once("The swapaccount= commandline option is deprecated. "
> +       bool res;
> +
> +       if (kstrtobool(s, &res) || !res)
> +               pr_warn_once("The swapaccount= commandline option is deprecated. "
>                      "Please report your usecase to linux-mm@kvack.org if you "
>                      "depend on this functionality.\n");
>         return 1;
> --

Yes, this makes sense to me, but I still think explicitly specifying
that swap accounting is always on now would make things even clearer.

Re: swapaccount= commandline option

[Johannes Weiner]

On Tue, Feb 13, 2024 at 08:01:37AM +0100, Narcis Garcia wrote:
> El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> >>
> >> Hello,
> >>
> >> I read this warning on Linux 6.1 boot:
> >> The swapaccount= commandline option is deprecated. Please report your
> >> usecase to linux-mm@kvack.org if you depend on this functionality.
> >>
> >> And I want to know if this impacts on LinuX Containers (LXC) swap
> >> accounting.
> > 
> > swapaccount= was deprecated in the sense that it is always on now
> > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > swapaccount=1 and want to make sure that swap accounting will still
> > work with v6.1, right?
> > 
> > This is the second question we have had about this message [1]. I
> > think we need to clarify the warning (and perhaps backport to stable
> > kernels).
> > 
> > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
> 
> 
> Thank you for answering this question, and sure this clarification is 
> needed both in documentation and warning message.
> I've found deprecation message was commited on 26 Sep 2022.
>  From what Linux version release, this deprecation is included?

Thanks for reporting this. I sent out a patch to only warn when
disabling is requested, and clarify the message a bit.

The knob was deprecated in Linux 6.1.

Re: swapaccount= commandline option

[Johannes Weiner]

On Tue, Feb 13, 2024 at 09:06:29AM +0100, Michal Hocko wrote:
> On Tue 13-02-24 08:01:37, Narcis Garcia wrote:
> > El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> > > > 
> > > > Hello,
> > > > 
> > > > I read this warning on Linux 6.1 boot:
> > > > The swapaccount= commandline option is deprecated. Please report your
> > > > usecase to linux-mm@kvack.org if you depend on this functionality.
> > > > 
> > > > And I want to know if this impacts on LinuX Containers (LXC) swap
> > > > accounting.
> > > 
> > > swapaccount= was deprecated in the sense that it is always on now
> > > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > > swapaccount=1 and want to make sure that swap accounting will still
> > > work with v6.1, right?
> > > 
> > > This is the second question we have had about this message [1]. I
> > > think we need to clarify the warning (and perhaps backport to stable
> > > kernels).
> > > 
> > > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
> > 
> > 
> > Thank you for answering this question, and sure this clarification is needed
> > both in documentation and warning message.
> > I've found deprecation message was commited on 26 Sep 2022.
> > From what Linux version release, this deprecation is included?
> > 
> > I suggest this for setup_swap_account() code:
> > pr_warn_once("The swapaccount= commandline option is deprecated. "
> > 	"Swap accounting is always on. "
> > 	"Please report your usecase to linux-mm@kvack.org if you "
> > 	"depend on this functionality.\n");
> 
> Would it make more sense to warn only if somebody tries to disable the
> swap accounting?

Gah, I should have refreshed my mail one more time before sending my
patch... Sorry about that.

> --- 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e4c8735e7c85..dec75eedf634 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7936,7 +7936,10 @@ bool mem_cgroup_swap_full(struct folio *folio)
>  
>  static int __init setup_swap_account(char *s)
>  {
> -	pr_warn_once("The swapaccount= commandline option is deprecated. "
> +	bool res;
> +
> +	if (kstrtobool(s, &res) || !res)
> +		pr_warn_once("The swapaccount= commandline option is deprecated. "
>  		     "Please report your usecase to linux-mm@kvack.org if you "
>  		     "depend on this functionality.\n");
>  	return 1;

Yes, I think that's the right thing to do.

Re: swapaccount= commandline option

[Johannes Weiner]

On Tue, Feb 13, 2024 at 12:09:26AM -0800, Yosry Ahmed wrote:
> On Tue, Feb 13, 2024 at 12:06 AM Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Tue 13-02-24 08:01:37, Narcis Garcia wrote:
> > > El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > > > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> > > > >
> > > > > Hello,
> > > > >
> > > > > I read this warning on Linux 6.1 boot:
> > > > > The swapaccount= commandline option is deprecated. Please report your
> > > > > usecase to linux-mm@kvack.org if you depend on this functionality.
> > > > >
> > > > > And I want to know if this impacts on LinuX Containers (LXC) swap
> > > > > accounting.
> > > >
> > > > swapaccount= was deprecated in the sense that it is always on now
> > > > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > > > swapaccount=1 and want to make sure that swap accounting will still
> > > > work with v6.1, right?
> > > >
> > > > This is the second question we have had about this message [1]. I
> > > > think we need to clarify the warning (and perhaps backport to stable
> > > > kernels).
> > > >
> > > > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
> > >
> > >
> > > Thank you for answering this question, and sure this clarification is needed
> > > both in documentation and warning message.
> > > I've found deprecation message was commited on 26 Sep 2022.
> > > From what Linux version release, this deprecation is included?
> > >
> > > I suggest this for setup_swap_account() code:
> > > pr_warn_once("The swapaccount= commandline option is deprecated. "
> > >       "Swap accounting is always on. "
> > >       "Please report your usecase to linux-mm@kvack.org if you "
> > >       "depend on this functionality.\n");
> >
> > Would it make more sense to warn only if somebody tries to disable the
> > swap accounting?
> > ---
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index e4c8735e7c85..dec75eedf634 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -7936,7 +7936,10 @@ bool mem_cgroup_swap_full(struct folio *folio)
> >
> >  static int __init setup_swap_account(char *s)
> >  {
> > -       pr_warn_once("The swapaccount= commandline option is deprecated. "
> > +       bool res;
> > +
> > +       if (kstrtobool(s, &res) || !res)
> > +               pr_warn_once("The swapaccount= commandline option is deprecated. "
> >                      "Please report your usecase to linux-mm@kvack.org if you "
> >                      "depend on this functionality.\n");
> >         return 1;
> > --
> 
> Yes, this makes sense to me, but I still think explicitly specifying
> that swap accounting is always on now would make things even clearer.

I think it's okay if it only warns when somebody requests disabling,
since the confusion won't happen anymore for folks still explicitly
requesting the enablement. I did add a blurb about what the preferred
method to control swap behavior is, though.

Re: swapaccount= commandline option

[Yosry Ahmed]

On Tue, Feb 13, 2024 at 12:26 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Tue, Feb 13, 2024 at 12:09:26AM -0800, Yosry Ahmed wrote:
> > On Tue, Feb 13, 2024 at 12:06 AM Michal Hocko <mhocko@suse.com> wrote:
> > >
> > > On Tue 13-02-24 08:01:37, Narcis Garcia wrote:
> > > > El 12/2/24 a les 23:37, Yosry Ahmed ha escrit:
> > > > > On Sun, Feb 11, 2024 at 1:33 AM Narcis Garcia <debianlists@actiu.net> wrote:
> > > > > >
> > > > > > Hello,
> > > > > >
> > > > > > I read this warning on Linux 6.1 boot:
> > > > > > The swapaccount= commandline option is deprecated. Please report your
> > > > > > usecase to linux-mm@kvack.org if you depend on this functionality.
> > > > > >
> > > > > > And I want to know if this impacts on LinuX Containers (LXC) swap
> > > > > > accounting.
> > > > >
> > > > > swapaccount= was deprecated in the sense that it is always on now
> > > > > (i.e. you cannot do swapaccount=0 anymore). I believe you are using
> > > > > swapaccount=1 and want to make sure that swap accounting will still
> > > > > work with v6.1, right?
> > > > >
> > > > > This is the second question we have had about this message [1]. I
> > > > > think we need to clarify the warning (and perhaps backport to stable
> > > > > kernels).
> > > > >
> > > > > [1]https://lore.kernel.org/linux-mm/2593755.Xrv9ptJ69j@sinistra.local/
> > > >
> > > >
> > > > Thank you for answering this question, and sure this clarification is needed
> > > > both in documentation and warning message.
> > > > I've found deprecation message was commited on 26 Sep 2022.
> > > > From what Linux version release, this deprecation is included?
> > > >
> > > > I suggest this for setup_swap_account() code:
> > > > pr_warn_once("The swapaccount= commandline option is deprecated. "
> > > >       "Swap accounting is always on. "
> > > >       "Please report your usecase to linux-mm@kvack.org if you "
> > > >       "depend on this functionality.\n");
> > >
> > > Would it make more sense to warn only if somebody tries to disable the
> > > swap accounting?
> > > ---
> > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > > index e4c8735e7c85..dec75eedf634 100644
> > > --- a/mm/memcontrol.c
> > > +++ b/mm/memcontrol.c
> > > @@ -7936,7 +7936,10 @@ bool mem_cgroup_swap_full(struct folio *folio)
> > >
> > >  static int __init setup_swap_account(char *s)
> > >  {
> > > -       pr_warn_once("The swapaccount= commandline option is deprecated. "
> > > +       bool res;
> > > +
> > > +       if (kstrtobool(s, &res) || !res)
> > > +               pr_warn_once("The swapaccount= commandline option is deprecated. "
> > >                      "Please report your usecase to linux-mm@kvack.org if you "
> > >                      "depend on this functionality.\n");
> > >         return 1;
> > > --
> >
> > Yes, this makes sense to me, but I still think explicitly specifying
> > that swap accounting is always on now would make things even clearer.
>
> I think it's okay if it only warns when somebody requests disabling,
> since the confusion won't happen anymore for folks still explicitly
> requesting the enablement. I did add a blurb about what the preferred
> method to control swap behavior is, though.

You did s/swapaccount=/swapaccount=0/g, and I think that's good enough.