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AJvYcCU8gDasjbfeBk5Yti5t12lrYHWI0q+ESAaWP0PbGZvZnwZTCGzLadhCVRW4dr57UUthkIDdsCa+9A==@kvack.org X-Gm-Message-State: AOJu0YyLx18uF17cOeJ3vqtS9m+GnYTGcTWIO2Xe7f+dkp7cAQZddVsD gHJK8AgBBmz2J/7S9RlAn54XBmMNF8/sjH+QzZoOgjRDgmzrWVvp5Zg00BJpUiSJiAPiGgRv7ht 16UKjdNw3IXp2H1UswPRfGKo/a7xPKbvGpqdW X-Google-Smtp-Source: AGHT+IGHNioCV05B550z2HqdgbUh0S/Q4eiZK4coivQy8ntPYu+GO8YLiwCo3H1KXVMRJGwT6JD11juuGsuy611LTeQ= X-Received: by 2002:a05:6102:32d2:b0:4a4:7980:b9c7 with SMTP id ada2fe7eead31-4a8cfb83109mr1334887137.14.1729914975276; Fri, 25 Oct 2024 20:56:15 -0700 (PDT) MIME-Version: 1.0 References: <20241025012304.2473312-1-shakeel.butt@linux.dev> <20241025012304.2473312-6-shakeel.butt@linux.dev> In-Reply-To: <20241025012304.2473312-6-shakeel.butt@linux.dev> From: Yu Zhao Date: Fri, 25 Oct 2024 21:55:38 -0600 Message-ID: Subject: Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Hugh Dickins , Yosry Ahmed , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Meta kernel team Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: BCF8840004 X-Stat-Signature: dp7uhnnucwjdasgu9niwkaoughyni4mq X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1729914960-166811 X-HE-Meta: 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 5jHyTBx+ pHeFAl6eKz34ddvG0WWSfLCTl6B3wttGKSjFHMfA4WjRPmHuHttA5G2ZZtRUx+M0wK2YbNIghPZwtzi+2aal/GeKs3d5UdBiD52qEA4EItJJ1NbRcILvmY0uJ6VxivvL7Y+9CE3bURwvWi/rqp+MnxlSqzJUBdJnRh8WJu/FY0I09AvsjKk87PX/40ukcJs/ZJVkT 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 Thu, Oct 24, 2024 at 7:23=E2=80=AFPM Shakeel Butt wrote: > > While updating the generation of the folios, MGLRU requires that the > folio's memcg association remains stable. With the charge migration > deprecated, there is no need for MGLRU to acquire locks to keep the > folio and memcg association stable. > > Signed-off-by: Shakeel Butt > --- > mm/vmscan.c | 11 ----------- > 1 file changed, 11 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 29c098790b01..fd7171658b63 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3662,10 +3662,6 @@ static void walk_mm(struct mm_struct *mm, struct l= ru_gen_mm_walk *walk) > if (walk->seq !=3D max_seq) > break; Please remove the lingering `struct mem_cgroup *memcg` as well as folio_memcg_rcu(). Otherwise it causes both build and lockdep warnings. > - /* folio_update_gen() requires stable folio_memcg() */ > - if (!mem_cgroup_trylock_pages(memcg)) > - break; > - > /* the caller might be holding the lock for write */ > if (mmap_read_trylock(mm)) { > err =3D walk_page_range(mm, walk->next_addr, ULON= G_MAX, &mm_walk_ops, walk); > @@ -3673,8 +3669,6 @@ static void walk_mm(struct mm_struct *mm, struct lr= u_gen_mm_walk *walk) > mmap_read_unlock(mm); > } > > - mem_cgroup_unlock_pages(); > - > if (walk->batched) { > spin_lock_irq(&lruvec->lru_lock); > reset_batch_size(walk); > @@ -4096,10 +4090,6 @@ bool lru_gen_look_around(struct page_vma_mapped_wa= lk *pvmw) > } > } > > - /* folio_update_gen() requires stable folio_memcg() */ > - if (!mem_cgroup_trylock_pages(memcg)) > - return true; > - > arch_enter_lazy_mmu_mode(); > > pte -=3D (addr - start) / PAGE_SIZE; > @@ -4144,7 +4134,6 @@ bool lru_gen_look_around(struct page_vma_mapped_wal= k *pvmw) > } > > arch_leave_lazy_mmu_mode(); > - mem_cgroup_unlock_pages(); > > /* feedback from rmap walkers to page table walkers */ > if (mm_state && suitable_to_scan(i, young)) > -- > 2.43.5 > >