Re: [PATCH bpf-next v9 02/10] bpf: convert cgroup_bpf.progs to hlist

[Martin KaFai Lau <kafai@fb.com>]

On Fri, Jun 10, 2022 at 09:57:55AM -0700, Stanislav Fomichev wrote:
> This lets us reclaim some space to be used by new cgroup lsm slots.
> 
> Before:
> struct cgroup_bpf {
> 	struct bpf_prog_array *    effective[23];        /*     0   184 */
> 	/* --- cacheline 2 boundary (128 bytes) was 56 bytes ago --- */
> 	struct list_head           progs[23];            /*   184   368 */
> 	/* --- cacheline 8 boundary (512 bytes) was 40 bytes ago --- */
> 	u32                        flags[23];            /*   552    92 */
> 
> 	/* XXX 4 bytes hole, try to pack */
> 
> 	/* --- cacheline 10 boundary (640 bytes) was 8 bytes ago --- */
> 	struct list_head           storages;             /*   648    16 */
> 	struct bpf_prog_array *    inactive;             /*   664     8 */
> 	struct percpu_ref          refcnt;               /*   672    16 */
> 	struct work_struct         release_work;         /*   688    32 */
> 
> 	/* size: 720, cachelines: 12, members: 7 */
> 	/* sum members: 716, holes: 1, sum holes: 4 */
> 	/* last cacheline: 16 bytes */
> };
> 
> After:
> struct cgroup_bpf {
> 	struct bpf_prog_array *    effective[23];        /*     0   184 */
> 	/* --- cacheline 2 boundary (128 bytes) was 56 bytes ago --- */
> 	struct hlist_head          progs[23];            /*   184   184 */
> 	/* --- cacheline 5 boundary (320 bytes) was 48 bytes ago --- */
> 	u8                         flags[23];            /*   368    23 */
> 
> 	/* XXX 1 byte hole, try to pack */
> 
> 	/* --- cacheline 6 boundary (384 bytes) was 8 bytes ago --- */
> 	struct list_head           storages;             /*   392    16 */
> 	struct bpf_prog_array *    inactive;             /*   408     8 */
> 	struct percpu_ref          refcnt;               /*   416    16 */
> 	struct work_struct         release_work;         /*   432    72 */
> 
> 	/* size: 504, cachelines: 8, members: 7 */
> 	/* sum members: 503, holes: 1, sum holes: 1 */
> 	/* last cacheline: 56 bytes */
> };
> 
> Suggested-by: Jakub Sitnicki <jakub@cloudflare.com>
> Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Martin KaFai Lau <kafai@fb.com>