Expose per-page memcg information to BPF programs, so that a bpf_iter over page_owner can aggregate and filter allocations by memcg. Attributing an allocation to a specific cgroup needs its full cgroup path, not just the memcg name.
Split memcg info collection out of print_page_owner_memcg() into get_page_memcg_info(), which fills struct memcg_info and, when given a caller-provided buffer, writes the full cgroup path via cgroup_path(). print_page_owner_memcg() now consumes the struct; this introduces no functional change to the debugfs output. The helper takes a single READ_ONCE snapshot within one RCU read-side critical section, so the flags and cgroup path reflect a consistent view of the page. cgroup_path() returns the path relative to the cgroup hierarchy root, so memcg attribution works on both cgroup v1 and v2. Signed-off-by: Zhen Ni <[email protected]> --- kernel/bpf/helpers.c | 1 + mm/page_owner.c | 85 ++++++++++++++++++++++++++++++++++---------- mm/page_owner.h | 9 +++++ mm/page_owner_iter.c | 7 ++++ 4 files changed, 83 insertions(+), 19 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 3e8afd19a1f4..b07a4dc46b58 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -4952,6 +4952,7 @@ BTF_ID_FLAGS(func, bpf_iter_page_owner_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLE BTF_ID_FLAGS(func, bpf_iter_page_owner_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_page_owner_stack_snprint, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_page_owner_get_nid, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_page_owner_get_memcg_info, KF_SLEEPABLE) #endif BTF_ID_FLAGS(func, __bpf_trap) BTF_ID_FLAGS(func, bpf_strcmp, KF_PERFMON); diff --git a/mm/page_owner.c b/mm/page_owner.c index 43a722678acc..ad503422b0c4 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -538,16 +538,22 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m, #ifdef CONFIG_MEMCG /* - * Looking for memcg information and print it out + * Collect memcg information of @page into @info; when @buf and a + * nonzero @size are given, also copy the full cgroup path of the + * charged memcg into @buf. + * + * Return: 0 if @page is charged to an attributable memcg; -ENODATA + * otherwise. */ -static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, - struct page *page) +int get_page_memcg_info(struct page *page, struct memcg_info *info, + char *buf, int size) { unsigned long memcg_data; struct obj_cgroup *objcg; struct mem_cgroup *memcg; - bool online; - char name[80]; + int ret = -ENODATA; + + *info = (struct memcg_info){}; rcu_read_lock(); memcg_data = READ_ONCE(page->memcg_data); @@ -555,31 +561,68 @@ static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, goto out_unlock; if (memcg_data & MEMCG_DATA_OBJEXTS) { - ret += scnprintf(kbuf + ret, count - ret, - "Slab cache page\n"); + info->is_slab = true; goto out_unlock; } objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK); - memcg = objcg ? obj_cgroup_memcg(objcg) : NULL; + if (!objcg) + goto out_unlock; + + memcg = obj_cgroup_memcg(objcg); if (!memcg) goto out_unlock; - online = css_is_online(&memcg->css); - cgroup_name(memcg->css.cgroup, name, sizeof(name)); - ret += scnprintf(kbuf + ret, count - ret, - "Charged %sto %smemcg %s\n", - (memcg_data & MEMCG_DATA_KMEM) ? "(via objcg) " : "", - online ? "" : "offline ", - name); + info->is_kmem = (memcg_data & MEMCG_DATA_KMEM) != 0; + info->is_online = css_is_online(&memcg->css); + cgroup_name(memcg->css.cgroup, info->name, sizeof(info->name)); + + if (buf && size) + cgroup_path(memcg->css.cgroup, buf, size); + ret = 0; out_unlock: rcu_read_unlock(); + if (ret < 0 && buf && size) + buf[0] = '\0'; + + return ret; +} + +/* + * Print memcg information from memcg_info + */ +static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, + const struct memcg_info *info) +{ + if (!info) + return ret; + + if (info->is_slab) + ret += scnprintf(kbuf + ret, count - ret, + "Slab cache page\n"); + + if (info->name[0]) + ret += scnprintf(kbuf + ret, count - ret, + "Charged %sto %smemcg %s\n", + info->is_kmem ? "(via objcg) " : "", + info->is_online ? "" : "offline ", + info->name); + return ret; } #else +int get_page_memcg_info(struct page *page, struct memcg_info *info, + char *buf, int size) +{ + *info = (struct memcg_info){}; + if (buf && size) + buf[0] = '\0'; + return -EOPNOTSUPP; +} + static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, - struct page *page) + const struct memcg_info *info) { return ret; } @@ -589,7 +632,8 @@ static ssize_t print_page_owner(char __user *buf, size_t count, unsigned long pfn, struct page *page, struct page_owner *page_owner, depot_stack_handle_t handle, - struct page_owner_filter_state *state) + struct page_owner_filter_state *state, + const struct memcg_info *memcg_info) { int ret, pageblock_mt, page_mt; char *kbuf; @@ -639,7 +683,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, migrate_reason_names[page_owner->last_migrate_reason]); } - ret = print_page_owner_memcg(kbuf, count, ret, page); + ret = print_page_owner_memcg(kbuf, count, ret, memcg_info); ret += snprintf(kbuf + ret, count - ret, "\n"); if (ret >= count) @@ -810,6 +854,7 @@ static ssize_t read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct page_owner_scan scan; + struct memcg_info memcg_info; struct page_owner_filter_state *state = file->private_data; if (!static_branch_unlikely(&page_owner_inited)) @@ -832,8 +877,10 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) /* Record the next PFN to read in the file offset */ *ppos = scan.pfn + 1; + get_page_memcg_info(scan.page, &memcg_info, NULL, 0); return print_page_owner(buf, count, scan.pfn, scan.page, - &scan.po_snap, scan.po_snap.handle, state); + &scan.po_snap, scan.po_snap.handle, state, + &memcg_info); skip_continue: scan.pfn++; cond_resched(); diff --git a/mm/page_owner.h b/mm/page_owner.h index c57859d18dc3..e74fc664d9b1 100644 --- a/mm/page_owner.h +++ b/mm/page_owner.h @@ -38,8 +38,17 @@ struct page_owner_scan { struct page_owner po_snap; }; +struct memcg_info { + char name[80]; + bool is_slab; + bool is_kmem; + bool is_online; +}; + bool page_owner_next_eligible(struct page_owner_scan *scan); int page_owner_get_nid(struct page *page); +int get_page_memcg_info(struct page *page, struct memcg_info *info, + char *buf, int size); /* * mm/page_owner_iter.c diff --git a/mm/page_owner_iter.c b/mm/page_owner_iter.c index 907517a29144..e7a8ca1e90e8 100644 --- a/mm/page_owner_iter.c +++ b/mm/page_owner_iter.c @@ -170,4 +170,11 @@ __bpf_kfunc int bpf_page_owner_get_nid(struct page_owner_scan *scan) return page_owner_get_nid(scan->page); } +__bpf_kfunc int bpf_page_owner_get_memcg_info(struct page_owner_scan *scan, + struct memcg_info *info, + char *buf, u32 size) +{ + return get_page_memcg_info(scan->page, info, buf, size); +} + __bpf_kfunc_end_defs(); -- 2.20.1
