+ maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch added to mm-unstable branch

+ maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: maple_tree: shrink struct maple_tree from 24 to 16 bytes on LP64
has been added to the -mm mm-unstable branch.  Its filename is
     maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
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------------------------------------------------------
From: Mateusz Guzik <mjguzik@gmail.com>
Subject: maple_tree: shrink struct maple_tree from 24 to 16 bytes on LP64
Date: Tue, 22 Aug 2023 00:51:45 +0200

by plugging a padding hole.

Link: https://lkml.kernel.org/r/20230821225145.2169848-1-mjguzik@gmail.com
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/maple_tree.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/maple_tree.h~maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64
+++ a/include/linux/maple_tree.h
@@ -220,8 +220,8 @@ struct maple_tree {
 		spinlock_t	ma_lock;
 		lockdep_map_p	ma_external_lock;
 	};
-	void __rcu      *ma_root;
 	unsigned int	ma_flags;
+	void __rcu      *ma_root;
 };
 
 /**
_

Patches currently in -mm which might be from mjguzik@gmail.com are

maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch

Re: + maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch added to mm-unstable branch

[Matthew Wilcox]

On Tue, Aug 22, 2023 at 11:44:54AM -0700, Andrew Morton wrote:
> ------------------------------------------------------
> From: Mateusz Guzik <mjguzik@gmail.com>
> Subject: maple_tree: shrink struct maple_tree from 24 to 16 bytes on LP64
> Date: Tue, 22 Aug 2023 00:51:45 +0200
> 
> by plugging a padding hole.
> 
> Link: https://lkml.kernel.org/r/20230821225145.2169848-1-mjguzik@gmail.com
> Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---

Could we perhaps amend the commit log?

Subject: maple_tree: Shrink struct maple_tree

Pack the members of struct maple_tree to avoid holes on 64-bit.
The size shrinks from 24 to 16 bytes which will save eight bytes
in every structure which embeds it.

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Re: + maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch added to mm-unstable branch

[Mateusz Guzik]

On 8/22/23, Matthew Wilcox <willy@infradead.org> wrote:
> On Tue, Aug 22, 2023 at 11:44:54AM -0700, Andrew Morton wrote:
>> ------------------------------------------------------
>> From: Mateusz Guzik <mjguzik@gmail.com>
>> Subject: maple_tree: shrink struct maple_tree from 24 to 16 bytes on LP64
>> Date: Tue, 22 Aug 2023 00:51:45 +0200
>>
>> by plugging a padding hole.
>>
>> Link:
>> https://lkml.kernel.org/r/20230821225145.2169848-1-mjguzik@gmail.com
>> Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
>> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>> ---
>
> Could we perhaps amend the commit log?
>
> Subject: maple_tree: Shrink struct maple_tree
>
> Pack the members of struct maple_tree to avoid holes on 64-bit.
> The size shrinks from 24 to 16 bytes which will save eight bytes
> in every structure which embeds it.
>
> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
>

Is this kind of descriptiveness expected? I am only a sojourner here,
but even then I suspect I'm going to run into a bunch of other
trivialities of this sort.

fwiw I would avoid the term 'pack' as it suggests the attribute
"packed", perhaps:

> Reorder the members of struct maple_tree to avoid holes on 64-bit.
> The size shrinks from 24 to 16 bytes which will save eight bytes
> in every structure which embeds it.

-- 
Mateusz Guzik <mjguzik gmail.com>

Re: + maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch added to mm-unstable branch

[Matthew Wilcox]

On Tue, Aug 22, 2023 at 08:57:46PM +0200, Mateusz Guzik wrote:
> On 8/22/23, Matthew Wilcox <willy@infradead.org> wrote:
> > On Tue, Aug 22, 2023 at 11:44:54AM -0700, Andrew Morton wrote:
> >> ------------------------------------------------------
> >> From: Mateusz Guzik <mjguzik@gmail.com>
> >> Subject: maple_tree: shrink struct maple_tree from 24 to 16 bytes on LP64
> >> Date: Tue, 22 Aug 2023 00:51:45 +0200
> >>
> >> by plugging a padding hole.
> >>
> >> Link:
> >> https://lkml.kernel.org/r/20230821225145.2169848-1-mjguzik@gmail.com
> >> Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
> >> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> >> Cc: Matthew Wilcox <willy@infradead.org>
> >> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> >> ---
> >
> > Could we perhaps amend the commit log?
> >
> > Subject: maple_tree: Shrink struct maple_tree
> >
> > Pack the members of struct maple_tree to avoid holes on 64-bit.
> > The size shrinks from 24 to 16 bytes which will save eight bytes
> > in every structure which embeds it.
> >
> > Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> >
> 
> Is this kind of descriptiveness expected? I am only a sojourner here,
> but even then I suspect I'm going to run into a bunch of other
> trivialities of this sort.

Generally, yes, descriptiveness is expected.  I acknowledge it can
be hard to think of what to say, particularly for a one-line patch.

Specifically, the term "LP64" is rarely used; 64-bit or CONFIG_64BIT is
more common.  It's also uncommon to continue a sentence fragment from
the Subject line into the body.

> fwiw I would avoid the term 'pack' as it suggests the attribute
> "packed", perhaps:
> 
> > Reorder the members of struct maple_tree to avoid holes on 64-bit.
> > The size shrinks from 24 to 16 bytes which will save eight bytes
> > in every structure which embeds it.

Works for me!

Re: + maple_tree-shrink-struct-maple_tree-from-24-to-16-bytes-on-lp64.patch added to mm-unstable branch

[Andrew Morton]

On Tue, 22 Aug 2023 19:49:07 +0100 Matthew Wilcox <willy@infradead.org> wrote:

> Subject: maple_tree: Shrink struct maple_tree
> 
> Pack the members of struct maple_tree to avoid holes on 64-bit.
> The size shrinks from 24 to 16 bytes which will save eight bytes
> in every structure which embeds it.
> 
> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

added, thanks.