Re: [PATCH] libceph: improve packing in struct ceph_osd_req_op

[Josh Durgin <josh.durgin@inktank.com>]

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

On 02/16/2013 08:24 AM, Alex Elder wrote:
> The layout of struct ceph_osd_req_op leaves lots of holes.
> Rearranging things a little for better field alignment
> reduces the size by a third.
>
> Signed-off-by: Alex Elder <elder@inktank.com>
> ---
>   include/linux/ceph/osd_client.h |   15 ++++++++-------
>   1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/ceph/osd_client.h
> b/include/linux/ceph/osd_client.h
> index 69287cc..82bf633 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -157,6 +157,7 @@ struct ceph_osd_client {
>
>   struct ceph_osd_req_op {
>   	u16 op;           /* CEPH_OSD_OP_* */
> +	u32 payload_len;
>   	union {
>   		struct {
>   			u64 offset, length;
> @@ -165,23 +166,24 @@ struct ceph_osd_req_op {
>   		} extent;
>   		struct {
>   			const char *name;
> -			u32 name_len;
>   			const char  *val;
> +			u32 name_len;
>   			u32 value_len;
>   			__u8 cmp_op;       /* CEPH_OSD_CMPXATTR_OP_* */
>   			__u8 cmp_mode;     /* CEPH_OSD_CMPXATTR_MODE_* */
>   		} xattr;
>   		struct {
>   			const char *class_name;
> -			__u8 class_len;
>   			const char *method_name;
> -			__u8 method_len;
> -			__u8 argc;
>   			const char *indata;
>   			u32 indata_len;
> +			__u8 class_len;
> +			__u8 method_len;
> +			__u8 argc;
>   		} cls;
>   		struct {
> -			u64 cookie, count;
> +			u64 cookie;
> +			u64 count;
>   		} pgls;
>   	        struct {
>   		        u64 snapid;
> @@ -189,12 +191,11 @@ struct ceph_osd_req_op {
>   		struct {
>   			u64 cookie;
>   			u64 ver;
> -			__u8 flag;
>   			u32 prot_ver;
>   			u32 timeout;
> +			__u8 flag;
>   		} watch;
>   	};
> -	u32 payload_len;
>   };
>
>   extern int ceph_osdc_init(struct ceph_osd_client *osdc,
>