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From: Shakeel Butt To: Roman Gushchin 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: X-Migadu-Flow: FLOW_OUT X-Stat-Signature: h1wyt4c1okmb3t4bfrwdtdhoxhmb88ik X-Rspam-User: X-Rspamd-Queue-Id: 011211A000F X-Rspamd-Server: rspam05 X-HE-Tag: 1714420589-109079 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 Mon, Apr 29, 2024 at 09:06:23AM -0700, Roman Gushchin wrote: > 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. No extra concern, just want this indirection table to be up to date in future.