On Thu, Dec 07, 2023 at 08:46:14AM -0500, Waiman Long <longman@xxxxxxxxxx> wrote:
> Commit 77070eeb8821 ("cgroup: Avoid false cacheline sharing of read
> mostly rstat_cpu") happens to be the last straw that breaks it.
FTR, when I build kernel from that commit, I can see
> struct cgroup_root {
> struct kernfs_root * kf_root; /* 0 8 */
> unsigned int subsys_mask; /* 8 4 */
> int hierarchy_id; /* 12 4 */
>
> /* XXX 48 bytes hole, try to pack */
>
> /* --- cacheline 1 boundary (64 bytes) --- */
> struct cgroup cgrp __attribute__((__aligned__(64))); /* 64 2368 */
>
> /* XXX last struct has 8 bytes of padding */
>
> /* --- cacheline 38 boundary (2432 bytes) --- */
> struct cgroup * cgrp_ancestor_storage; /* 2432 8 */
> atomic_t nr_cgrps; /* 2440 4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct list_head root_list; /* 2448 16 */
> struct callback_head rcu __attribute__((__aligned__(8))); /* 2464 16 */
> unsigned int flags; /* 2480 4 */
> char release_agent_path[4096]; /* 2484 4096 */
> /* --- cacheline 102 boundary (6528 bytes) was 52 bytes ago --- */
> char name[64]; /* 6580 64 */
>
> /* size: 6656, cachelines: 104, members: 11 */
> /* sum members: 6592, holes: 2, sum holes: 52 */
> /* padding: 12 */
> /* paddings: 1, sum paddings: 8 */
> /* forced alignments: 2, forced holes: 1, sum forced holes: 48 */
> } __attribute__((__aligned__(64)));
2480 has still quite a reserve below 4096. (I can't see an CONFIG_*
affecting this.)
Perhaps, I missed something from the linux-next merging thread?
Michal
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