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[109.81.25.183]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a18bf214a1sm499703195e9.7.2026.10.14.04.29.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Oct 2026 04:29:28 -0700 (PDT) Date: Wed, 14 Oct 2026 13:29:26 +0200 From: Michal Hocko To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Roman Gushchin , Muchun Song , Tejun Heo , Meta kernel team , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH for-7.5 3/5] memcg: use high_work for remote charges Message-ID: References: <20261010210957.1350874-1-shakeel.butt@linux.dev> <20261010210957.1350874-4-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261010210957.1350874-4-shakeel.butt@linux.dev> On Sat 10-10-26 14:09:55, Shakeel Butt wrote: > Some charges go to a cgroup outside the current mm's cgroup and its > ancestors. The high handler uses current->mm, so it cannot handle these > overages. Filesystem notifications and remote page faults can take > this path. Hmm, you made me look at other places in the charge path where we are assuming current->memcg == memcg. We have reclaim recursion and oom checks. The former makes sense, for the latter it is likely not harmful. > Use mm_match_cgroup() before checking the high limits. If it does not > match, use high_work instead of recording task overage or doing > synchronous reclaim and throttling. Charges to the same cgroup or an > ancestor keep their current handling. Tasks without an mm also use the > worker. > > Like kernel threads, remote chargers skip memory.swap.high throttling > and its high-event reporting, and a fast allocator can outrun the worker. > The memory.max and memory.swap.max checks stay the same. Makes sense. > Suggested-by: Tejun Heo > Signed-off-by: Shakeel Butt Acked-by: Michal Hocko Thanks! > --- > mm/memcontrol.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 8116fce6ab96..3456960cbe68 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2705,7 +2705,8 @@ static void memcg_enforce_high(struct mem_cgroup *memcg, unsigned int nr_pages, > gfp_t gfp_mask) > { > bool allow_spinning = gfpflags_allow_spinning(gfp_mask); > - bool use_worker = !in_task() || (current->flags & PF_KTHREAD); > + bool use_worker = !in_task() || (current->flags & PF_KTHREAD) || > + !current->mm || !mm_match_cgroup(current->mm, memcg); > > /* > * If the hierarchy is above the normal consumption range, schedule > @@ -2728,6 +2729,7 @@ static void memcg_enforce_high(struct mem_cgroup *memcg, unsigned int nr_pages, > * Don't make an unrelated interrupted task handle this charge. > * Kernel threads may be working for other tasks, so let a worker > * reclaim instead. > + * Remote charges need reclaim from their charged hierarchy. > */ > if (use_worker) { > if (mem_high) { > @@ -2756,7 +2758,7 @@ static void memcg_enforce_high(struct mem_cgroup *memcg, unsigned int nr_pages, > } > } while ((memcg = parent_mem_cgroup(memcg))); > > - /* Interrupts and kernel threads stop here. */ > + /* Interrupts, kernel threads, and remote chargers stop here. */ > if (use_worker) > return; > > -- > 2.53.0-Meta -- Michal Hocko SUSE Labs