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From: Roman Gushchin To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 5/7] memcg: pr_warn_once for unexpected events and stats Message-ID: References: <20240427003733.3898961-1-shakeel.butt@linux.dev> <20240427003733.3898961-6-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240427003733.3898961-6-shakeel.butt@linux.dev> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: C18B6C000A X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 7n38io9z6y58kbk1e59yq4fpngskt8dm X-HE-Tag: 1714406788-701694 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 26, 2024 at 05:37:31PM -0700, Shakeel Butt 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 > --- > 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); > } I think it's generally a CONFIG_DEBUG_VM material. Do we have some extra concerns here? Having pr_warn_on_once() would be nice here.