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AJvYcCUgZHWeIYo9cRz0EcSdK5TU8S0nWgQ7Dj+Q1aIgwB33Iu50qRlzVNcjGNb7LtOC8xUjSV7i8ub4Wi06sNNiPCjFLGs= X-Gm-Message-State: AOJu0YySfn2Ag1K9wkSYyk2D6Oz98CRApt7PQoIxqAnPWZpkNS9mOARw v/mSnYQZjEGCyuAvk+P6UsC+Tx86NBzOa7dodzS5dodsZWpOPfK86JkEd83Bcj/IuStOknB2Eej jkerQKDXh8C45fkTile58w++7zlXyu0UCbQlD X-Google-Smtp-Source: AGHT+IHvTq7qhe5Gj4WiZ0O8rfvc72H94d5tMQE1Rjx0WZKcH4BC6WYPuiGa8QxBJcIIiaX/2Rd+QFMNsz7dirDTnlw= X-Received: by 2002:a17:906:2dda:b0:a55:9e16:f005 with SMTP id h26-20020a1709062dda00b00a559e16f005mr2853749eji.57.1714178606615; Fri, 26 Apr 2024 17:43:26 -0700 (PDT) MIME-Version: 1.0 References: <20240427003733.3898961-1-shakeel.butt@linux.dev> <20240427003733.3898961-2-shakeel.butt@linux.dev> In-Reply-To: <20240427003733.3898961-2-shakeel.butt@linux.dev> From: Yosry Ahmed Date: Fri, 26 Apr 2024 17:42:48 -0700 Message-ID: Subject: Re: [PATCH v2 1/7] memcg: reduce memory size of mem_cgroup_events_index To: Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 82C391C000D X-Rspamd-Server: rspam06 X-Stat-Signature: xfwq7wbdf98dh1bz899aa6mtzm3zbpq8 X-HE-Tag: 1714178608-168868 X-HE-Meta: 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 J8zaN3qX 5rH5CLHLNGzi6u1flBiicEWQyMwoncImW81TSbzLkRx7mBZBM5fd9NHul5w8LECp/AAjEnsvhE4+9w3lYibHokRgkobK4VEEzL4DdfeocobbwOjWRzUFzR01XYm7vKZ746BfX0aTlV6YS0CbA+JKBQgXak1hpn2C0uSGl16IAdsDjaYa6JGQYgyZw234UWBcr4wskVR40XCc2CwJmkeRTtBybkU3J9QzPIenpCtPwXuI+eef8LisY6d5jIa2+3ZlCouVoAORgMvtZQvY= 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 5:37=E2=80=AFPM Shakeel Butt wrote: > > mem_cgroup_events_index is a translation table to get the right index of > the memcg relevant entry for the general vm_event_item. At the moment, > it is defined as integer array. However on a typical system the max > entry of vm_event_item (NR_VM_EVENT_ITEMS) is 113, so we don't need to > use int as storage type of the array. For now just use int8_t as type > and add a BUILD_BUG_ON() and will switch to short once NR_VM_EVENT_ITEMS > touches 127. Any reason not to use uint8_t (or simply u8) and U8_MAX (instead of the hardcoded 127)? > > Signed-off-by: Shakeel Butt > --- > mm/memcontrol.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 602ad5faad4d..53769d06053f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -607,11 +607,14 @@ static const unsigned int memcg_vm_event_stat[] =3D= { > }; > > #define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat) > -static int mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; > +static int8_t mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly; > > static void init_memcg_events(void) > { > - int i; > + int8_t i; > + > + /* Switch to short once this failure occurs. */ > + BUILD_BUG_ON(NR_VM_EVENT_ITEMS >=3D 127 /* INT8_MAX */); > > for (i =3D 0; i < NR_MEMCG_EVENTS; ++i) > mem_cgroup_events_index[memcg_vm_event_stat[i]] =3D i + 1= ; > -- > 2.43.0 > >