| Message ID | c112aad16eb47808e1ec10abd87b3d273c969a68.1677704283.git.christophe.jaillet@wanadoo.fr |
|---|---|
| State | Accepted |
| Commit | ae2ade4ba58167f165fbf3db19380f9b72c56db8 |
| Headers | show |
| Series | spi: Reorder fields in 'struct spi_message' | expand |
On 3/2/23 1:58 AM, Christophe JAILLET wrote: > Group some variables based on their sizes to reduce hole and avoid padding. > On x86_64, this shrinks the size from 112 to 96 bytes. > > This should have no real impact on memory allocation because 'struct > spi_message' is mostly used on stack, but it can save a few cycles > when the structure is initialized with spi_message_init() and co. > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com> Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com> > --- > Using pahole > > Before: > ====== > struct spi_message { > struct list_head transfers; /* 0 16 */ > struct spi_device * spi; /* 16 8 */ > unsigned int is_dma_mapped:1; /* 24: 0 4 */ > > /* XXX 31 bits hole, try to pack */ > /* XXX 4 bytes hole, try to pack */ > > void (*complete)(void *); /* 32 8 */ > void * context; /* 40 8 */ > unsigned int frame_length; /* 48 4 */ > unsigned int actual_length; /* 52 4 */ > int status; /* 56 4 */ > > /* XXX 4 bytes hole, try to pack */ > > /* --- cacheline 1 boundary (64 bytes) --- */ > struct list_head queue; /* 64 16 */ > void * state; /* 80 8 */ > struct list_head resources; /* 88 16 */ > bool prepared; /* 104 1 */ > > /* size: 112, cachelines: 2, members: 12 */ > /* sum members: 93, holes: 2, sum holes: 8 */ > /* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 31 bits */ > /* padding: 7 */ > /* last cacheline: 48 bytes */ > }; > > > After: > ===== > struct spi_message { > struct list_head transfers; /* 0 16 */ > struct spi_device * spi; /* 16 8 */ > unsigned int is_dma_mapped:1; /* 24: 0 4 */ > > /* XXX 7 bits hole, try to pack */ > /* Bitfield combined with next fields */ > > bool prepared; /* 25 1 */ > > /* XXX 2 bytes hole, try to pack */ > > int status; /* 28 4 */ > void (*complete)(void *); /* 32 8 */ > void * context; /* 40 8 */ > unsigned int frame_length; /* 48 4 */ > unsigned int actual_length; /* 52 4 */ > struct list_head queue; /* 56 16 */ > /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */ > void * state; /* 72 8 */ > struct list_head resources; /* 80 16 */ > > /* size: 96, cachelines: 2, members: 12 */ > /* sum members: 93, holes: 1, sum holes: 2 */ > /* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 7 bits */ > /* last cacheline: 32 bytes */ > }; > --- > include/linux/spi/spi.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index 4fa26b9a3572..bdb35a91b4bf 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -1093,6 +1093,9 @@ struct spi_message { > > unsigned is_dma_mapped:1; > > + /* spi_prepare_message() was called for this message */ > + bool prepared; > + > /* REVISIT: we might want a flag affecting the behavior of the > * last transfer ... allowing things like "read 16 bit length L" > * immediately followed by "read L bytes". Basically imposing > @@ -1105,11 +1108,11 @@ struct spi_message { > */ > > /* Completion is reported through a callback */ > + int status; > void (*complete)(void *context); > void *context; > unsigned frame_length; > unsigned actual_length; > - int status; > > /* For optional use by whatever driver currently owns the > * spi_message ... between calls to spi_async and then later > @@ -1120,9 +1123,6 @@ struct spi_message { > > /* List of spi_res reources when the spi message is processed */ > struct list_head resources; > - > - /* spi_prepare_message() was called for this message */ > - bool prepared; > }; > > static inline void spi_message_init_no_memset(struct spi_message *m)
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 4fa26b9a3572..bdb35a91b4bf 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -1093,6 +1093,9 @@ struct spi_message { unsigned is_dma_mapped:1; + /* spi_prepare_message() was called for this message */ + bool prepared; + /* REVISIT: we might want a flag affecting the behavior of the * last transfer ... allowing things like "read 16 bit length L" * immediately followed by "read L bytes". Basically imposing @@ -1105,11 +1108,11 @@ struct spi_message { */ /* Completion is reported through a callback */ + int status; void (*complete)(void *context); void *context; unsigned frame_length; unsigned actual_length; - int status; /* For optional use by whatever driver currently owns the * spi_message ... between calls to spi_async and then later @@ -1120,9 +1123,6 @@ struct spi_message { /* List of spi_res reources when the spi message is processed */ struct list_head resources; - - /* spi_prepare_message() was called for this message */ - bool prepared; }; static inline void spi_message_init_no_memset(struct spi_message *m)
Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size from 112 to 96 bytes. This should have no real impact on memory allocation because 'struct spi_message' is mostly used on stack, but it can save a few cycles when the structure is initialized with spi_message_init() and co. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- Using pahole Before: ====== struct spi_message { struct list_head transfers; /* 0 16 */ struct spi_device * spi; /* 16 8 */ unsigned int is_dma_mapped:1; /* 24: 0 4 */ /* XXX 31 bits hole, try to pack */ /* XXX 4 bytes hole, try to pack */ void (*complete)(void *); /* 32 8 */ void * context; /* 40 8 */ unsigned int frame_length; /* 48 4 */ unsigned int actual_length; /* 52 4 */ int status; /* 56 4 */ /* XXX 4 bytes hole, try to pack */ /* --- cacheline 1 boundary (64 bytes) --- */ struct list_head queue; /* 64 16 */ void * state; /* 80 8 */ struct list_head resources; /* 88 16 */ bool prepared; /* 104 1 */ /* size: 112, cachelines: 2, members: 12 */ /* sum members: 93, holes: 2, sum holes: 8 */ /* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 31 bits */ /* padding: 7 */ /* last cacheline: 48 bytes */ }; After: ===== struct spi_message { struct list_head transfers; /* 0 16 */ struct spi_device * spi; /* 16 8 */ unsigned int is_dma_mapped:1; /* 24: 0 4 */ /* XXX 7 bits hole, try to pack */ /* Bitfield combined with next fields */ bool prepared; /* 25 1 */ /* XXX 2 bytes hole, try to pack */ int status; /* 28 4 */ void (*complete)(void *); /* 32 8 */ void * context; /* 40 8 */ unsigned int frame_length; /* 48 4 */ unsigned int actual_length; /* 52 4 */ struct list_head queue; /* 56 16 */ /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */ void * state; /* 72 8 */ struct list_head resources; /* 80 16 */ /* size: 96, cachelines: 2, members: 12 */ /* sum members: 93, holes: 1, sum holes: 2 */ /* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 7 bits */ /* last cacheline: 32 bytes */ }; --- include/linux/spi/spi.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)