Messages in this thread | | | Date | Thu, 7 Dec 2023 12:40:33 -0500 | Subject | Re: [PATCH-cgroup v2] cgroup: Move rcu_head up near the top of cgroup_root | From | Waiman Long <> |
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On 12/7/23 11:46, Michal Koutný wrote: > On Thu, Dec 07, 2023 at 08:46:14AM -0500, Waiman Long <longman@redhat.com> 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?
CONFIG_LOCKDEP and some other debug configs are enabled with allmodconfig. This can greatly increase the size of some of the structures. I am not able to use pahole due to missing BTF info so I don't the exact size. However, I can reproduce the build failure and the patch is able to fix it.
Cheers, Longman
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