On Fri, Apr 26, 2024 at 5:38 PM Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote:
>
> To reduce memory usage by the memcg events and stats, the kernel uses
> indirection table and only allocate stats and events which are being
> used by the memcg code. To make this more robust, let's add warnings
> where unexpected stats and events indexes are used.
>
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> ---
> mm/memcontrol.c | 43 ++++++++++++++++++++++++++++++++++---------
> 1 file changed, 34 insertions(+), 9 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 103e0e53e20a..36145089dcf5 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -671,9 +671,11 @@ unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx)
> return node_page_state(lruvec_pgdat(lruvec), idx);
>
> i = memcg_stats_index(idx);
> - if (i >= 0) {
> + if (likely(i >= 0)) {
> pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
> x = READ_ONCE(pn->lruvec_stats->state[i]);
> + } else {
> + pr_warn_once("%s: stat item index: %d\n", __func__, idx);
> }
Can we make these more compact by using WARN_ON_ONCE() instead:
if (WARN_ON_ONCE(i < 0))
return 0;
I guess the advantage of using pr_warn_once() is that we get to print
the exact stat index, but the stack trace from WARN_ON_ONCE() should
make it obvious in most cases AFAICT.
No strong opinions either way.
