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[2003:dc:6f4c:be00:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4ba020433casm132712185e9.7.2026.11.11.04.52.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 04:52:51 -0800 (PST) From: Max Kellermann To: tytso@mit.edu, adilger.kernel@dilger.ca, libaokun@linux.alibaba.com, jack@suse.cz, ojaswin@linux.ibm.com, ritesh.list@gmail.com, yi.zhang@huawei.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Max Kellermann Subject: [PATCH 0/3] ext4: reduce per-inode memory overhead Date: Wed, 11 Nov 2026 13:52:39 +0100 Message-ID: <20261111125242.1078620-1-max.kellermann@ionos.com> X-Mailer: git-send-email 2.53.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This series reduces the size of `struct ext4_inode_info` by improving timestamp packing and allowing fast commit and bigalloc support to be omitted at compile time. The incremental reductions are: Disable CONFIG_EXT4_FS_FAST_COMMIT 48 bytes Disable CONFIG_EXT4_FS_BIGALLOC 8 bytes Compact creation time, with fast commit off 8 bytes -------- Total 64 bytes On our production server with 35 million ext4 inode objects (a big fscache partition), this saves 2.1 GB RAM. Both new Kconfig options default to enabled. Without fast commit support, clean filesystems use ordinary journal commits; journals requiring fast commit recovery are rejected. Without bigalloc support, bigalloc filesystems are rejected before journal recovery, including for read-only mounts. Max Kellermann (3): ext4: make fast commit support optional ext4: make bigalloc support optional ext4: store creation time in separate seconds and nanoseconds Documentation/filesystems/ext4/bigalloc.rst | 6 ++ Documentation/filesystems/ext4/journal.rst | 7 ++ fs/ext4/Kconfig | 31 ++++++++ fs/ext4/Makefile | 3 +- fs/ext4/ext4.h | 83 +++++++++++++++++++-- fs/ext4/extents_status.c | 44 ++++++++++- fs/ext4/extents_status.h | 15 ++++ fs/ext4/ialloc.c | 3 +- fs/ext4/inode.c | 8 +- fs/ext4/super.c | 40 ++++++++-- fs/ext4/sysfs.c | 6 ++ include/trace/events/ext4.h | 3 + 12 files changed, 227 insertions(+), 22 deletions(-) -- 2.53.0