From: Tejun Heo <tj@xxxxxxxxxx> Subject: mm, memcontrol: implement memory.swap.events Add swap max and fail events so that userland can monitor and respond to running out of swap. I'm not too sure about the fail event. Right now, it's a bit confusing which stats / events are recursive and which aren't and also which ones reflect events which originate from a given cgroup and which targets the cgroup. No idea what the right long term solution is and it could just be that growing them organically is actually the only right thing to do. Link: http://lkml.kernel.org/r/20180416231151.GI1911913@xxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Cc: <linux-api@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/cgroup-v2.rst | 16 ++++++++++++++ include/linux/memcontrol.h | 5 ++++ mm/memcontrol.c | 24 +++++++++++++++++++++- 3 files changed, 44 insertions(+), 1 deletion(-) diff -puN Documentation/admin-guide/cgroup-v2.rst~mm-memcontrol-implement-memoryswapevents Documentation/admin-guide/cgroup-v2.rst --- a/Documentation/admin-guide/cgroup-v2.rst~mm-memcontrol-implement-memoryswapevents +++ a/Documentation/admin-guide/cgroup-v2.rst @@ -1199,6 +1199,22 @@ PAGE_SIZE multiple when read back. Swap usage hard limit. If a cgroup's swap usage reaches this limit, anonymous memory of the cgroup will not be swapped out. + memory.swap.events + A read-only flat-keyed file which exists on non-root cgroups. + The following entries are defined. Unless specified + otherwise, a value change in this file generates a file + modified event. + + max + The number of times the cgroup's swap usage was about + to go over the max boundary and swap allocation + failed. + + fail + The number of times swap allocation failed either + because of running out of swap system-wide or max + limit. + Usage Guidelines ~~~~~~~~~~~~~~~~ diff -puN include/linux/memcontrol.h~mm-memcontrol-implement-memoryswapevents include/linux/memcontrol.h --- a/include/linux/memcontrol.h~mm-memcontrol-implement-memoryswapevents +++ a/include/linux/memcontrol.h @@ -53,6 +53,8 @@ enum memcg_memory_event { MEMCG_HIGH, MEMCG_MAX, MEMCG_OOM, + MEMCG_SWAP_MAX, + MEMCG_SWAP_FAIL, MEMCG_NR_MEMORY_EVENTS, }; @@ -208,6 +210,9 @@ struct mem_cgroup { atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS]; struct cgroup_file events_file; + /* handle for "memory.swap.events" */ + struct cgroup_file swap_events_file; + /* protect arrays of thresholds */ struct mutex thresholds_lock; diff -puN mm/memcontrol.c~mm-memcontrol-implement-memoryswapevents mm/memcontrol.c --- a/mm/memcontrol.c~mm-memcontrol-implement-memoryswapevents +++ a/mm/memcontrol.c @@ -6012,13 +6012,17 @@ int mem_cgroup_try_charge_swap(struct pa if (!memcg) return 0; - if (!entry.val) + if (!entry.val) { + memcg_memory_event(memcg, MEMCG_SWAP_FAIL); return 0; + } memcg = mem_cgroup_id_get_online(memcg); if (!mem_cgroup_is_root(memcg) && !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) { + memcg_memory_event(memcg, MEMCG_SWAP_MAX); + memcg_memory_event(memcg, MEMCG_SWAP_FAIL); mem_cgroup_id_put(memcg); return -ENOMEM; } @@ -6156,6 +6160,18 @@ static ssize_t swap_max_write(struct ker return nbytes; } +static int swap_events_show(struct seq_file *m, void *v) +{ + struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m)); + + seq_printf(m, "max %lu\n", + atomic_long_read(&memcg->memory_events[MEMCG_SWAP_MAX])); + seq_printf(m, "fail %lu\n", + atomic_long_read(&memcg->memory_events[MEMCG_SWAP_FAIL])); + + return 0; +} + static struct cftype swap_files[] = { { .name = "swap.current", @@ -6168,6 +6184,12 @@ static struct cftype swap_files[] = { .seq_show = swap_max_show, .write = swap_max_write, }, + { + .name = "swap.events", + .flags = CFTYPE_NOT_ON_ROOT, + .file_offset = offsetof(struct mem_cgroup, swap_events_file), + .seq_show = swap_events_show, + }, { } /* terminate */ }; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
