Am Mittwoch, 6. Juni 2007 schrieb Pete Zaitcev:
> So, you add 24 bytes to all URBs, which are... not very thin, to be sure.
> Last time I counted they were 152 bytes apiece. Still, a 15% increase.
> I know you're a good algorithmist, are you sure you don't have any ideas?
>
> The naive approach is to have anchor elements out of line... In a slab,
> since they are fixed-sized. What do you think?
Here's a patch to reduce padding:
--- a/include/linux/usb.h 2007-06-06 13:44:41.000000000 +0200
+++ b/include/linux/usb.h 2007-06-06 14:29:43.000000000 +0200
@@ -1142,24 +1142,24 @@ struct urb
{
/* private: usb core and host controller only fields in the urb */
struct kref kref; /* reference count of the URB */
+ atomic_t use_count; /* concurrent submissions counter */
spinlock_t lock; /* lock for the URB */
void *hcpriv; /* private data for host controller */
- atomic_t use_count; /* concurrent submissions counter */
+ struct list_head anchor_list; /* the URB may be anchored by the
driver */
+ struct usb_anchor *anchor; /* anchor to which we are chained */
u8 reject; /* submissions will fail */
/* public: documented fields in the urb that can be used by drivers */
+ short status; /* (return) non-ISO status */
+ unsigned short transfer_flags; /* (in) URB_SHORT_NOT_OK | ...*/
+ unsigned int pipe; /* (in) pipe information */
+ int transfer_buffer_length; /* (in) data buffer length */
+ int actual_length; /* (return) actual transfer length */
struct list_head urb_list; /* list head for use by the urb's
* current owner */
- struct list_head anchor_list; /* the URB may be anchored by the
driver */
- struct usb_anchor *anchor;
struct usb_device *dev; /* (in) pointer to associated device */
- unsigned int pipe; /* (in) pipe information */
- int status; /* (return) non-ISO status */
- unsigned int transfer_flags; /* (in) URB_SHORT_NOT_OK | ...*/
void *transfer_buffer; /* (in) associated data buffer */
dma_addr_t transfer_dma; /* (in) dma addr for transfer_buffer */
- int transfer_buffer_length; /* (in) data buffer length */
- int actual_length; /* (return) actual transfer length */
unsigned char *setup_packet; /* (in) setup packet (control only) */
dma_addr_t setup_dma; /* (in) dma addr for setup_packet */
int start_frame; /* (modify) start frame (ISO) */
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