Messages in this thread Patch in this message | | | From | Christophe JAILLET <> | Subject | [PATCH] dmaengine: Reorder fields in 'struct dma_slave_config' | Date | Fri, 17 Feb 2023 15:23:00 +0100 |
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Group some variables based on their sizes to reduce hole and avoid padding. On x86_64, this shrinks the size of 'struct dma_slave_config' from 72 to 64 bytes.
This should save a few bytes of memory and a few cycles.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> --- Using pahole
Before: ====== struct dma_slave_config { enum dma_transfer_direction direction; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
phys_addr_t src_addr; /* 8 8 */ phys_addr_t dst_addr; /* 16 8 */ enum dma_slave_buswidth src_addr_width; /* 24 4 */ enum dma_slave_buswidth dst_addr_width; /* 28 4 */ u32 src_maxburst; /* 32 4 */ u32 dst_maxburst; /* 36 4 */ u32 src_port_window_size; /* 40 4 */ u32 dst_port_window_size; /* 44 4 */ bool device_fc; /* 48 1 */
/* XXX 7 bytes hole, try to pack */
void * peripheral_config; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ size_t peripheral_size; /* 64 8 */
/* size: 72, cachelines: 2, members: 12 */ /* sum members: 61, holes: 2, sum holes: 11 */ /* last cacheline: 8 bytes */ };
After: ===== struct dma_slave_config { enum dma_transfer_direction direction; /* 0 4 */ bool device_fc; /* 4 1 */
/* XXX 3 bytes hole, try to pack */
phys_addr_t src_addr; /* 8 8 */ phys_addr_t dst_addr; /* 16 8 */ enum dma_slave_buswidth src_addr_width; /* 24 4 */ enum dma_slave_buswidth dst_addr_width; /* 28 4 */ u32 src_maxburst; /* 32 4 */ u32 dst_maxburst; /* 36 4 */ u32 src_port_window_size; /* 40 4 */ u32 dst_port_window_size; /* 44 4 */ void * peripheral_config; /* 48 8 */ size_t peripheral_size; /* 56 8 */
/* size: 64, cachelines: 1, members: 12 */ /* sum members: 61, holes: 1, sum holes: 3 */ }; --- include/linux/dmaengine.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index c3656e590213..61e1d1da4446 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -390,6 +390,9 @@ enum dma_slave_buswidth { * legal values. DEPRECATED, drivers should use the direction argument * to the device_prep_slave_sg and device_prep_dma_cyclic functions or * the dir field in the dma_interleaved_template structure. + * @device_fc: Flow Controller Settings. Only valid for slave channels. Fill + * with 'true' if peripheral should be flow controller. Direction will be + * selected at Runtime. * @src_addr: this is the physical address where DMA slave data * should be read (RX), if the source is memory this argument is * ignored. @@ -415,9 +418,6 @@ enum dma_slave_buswidth { * loops in this area in order to transfer the data. * @dst_port_window_size: same as src_port_window_size but for the destination * port. - * @device_fc: Flow Controller Settings. Only valid for slave channels. Fill - * with 'true' if peripheral should be flow controller. Direction will be - * selected at Runtime. * @peripheral_config: peripheral configuration for programming peripheral * for dmaengine transfer * @peripheral_size: peripheral configuration buffer size @@ -436,6 +436,7 @@ enum dma_slave_buswidth { */ struct dma_slave_config { enum dma_transfer_direction direction; + bool device_fc; phys_addr_t src_addr; phys_addr_t dst_addr; enum dma_slave_buswidth src_addr_width; @@ -444,7 +445,6 @@ struct dma_slave_config { u32 dst_maxburst; u32 src_port_window_size; u32 dst_port_window_size; - bool device_fc; void *peripheral_config; size_t peripheral_size; }; -- 2.34.1
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