Messages in this thread | | | From | Yosry Ahmed <> | Date | Fri, 26 Apr 2024 17:58:16 -0700 | Subject | Re: [PATCH v2 5/7] memcg: pr_warn_once for unexpected events and stats |
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On Fri, Apr 26, 2024 at 5:38 PM Shakeel Butt <shakeel.butt@linux.dev> 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@linux.dev> > --- > 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.
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