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[2003:dc:6f45:eb00:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47a9de1d905sm22324916f8f.2.2026.07.06.00.24.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Jul 2026 00:24:55 -0700 (PDT) From: Max Kellermann To: idryomov@gmail.com, amarkuze@redhat.com, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Max Kellermann Subject: [PATCH v2 00/18] fs/ceph: optimize struct layouts Date: Mon, 6 Jul 2026 09:24:31 +0200 Message-ID: <20260706072450.3920010-1-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This patch set aims to reduce the memory usage of the Ceph filesystems by optimizing the layout of structs, most importantly struct ceph_inode_info: - use `bool` instead of `int` for booelans - use `u32` instead of `u64` where possible - reorder fields to eliminate padding holes - eliminate redundant fields Without this patch set, ceph_inode_info looks like this with pahole: /* size: 1456, cachelines: 23, members: 79 */ /* sum members: 1424, holes: 8, sum holes: 32 */ /* member types with holes: 3, total: 3 */ With this patch set, struct ceph_inode_info got smaller by 96 bytes: /* size: 1360, cachelines: 22, members: 76 */ /* member types with holes: 1, total: 1 */ struct ceph_cap shrinks by 24 bytes: /* size: 120, cachelines: 2, members: 12 */ /* size: 96, cachelines: 2, members: 10 */ struct ceph_snap_realm shrinks by 24 bytes, too: /* size: 232, cachelines: 4, members: 21 */ /* sum members: 216, holes: 3, sum holes: 12 */ /* size: 208, cachelines: 4, members: 20 */ --- v1->v2: - fix CONFIG_FS_ENCRYPTION check in "i_truncate_pagecache_size" patch - add patches to shrink ceph_cap and ceph_snap_realm Max Kellermann (18): fs/ceph/super: remove unused field `i_cap_migration_resv` fs/ceph/super: make field `i_truncate_pagecache_size` optional include/ceph/ceph_fs.h: convert `pool_id` to u32 fs/ceph/super.h: convert ceph_inode_xattr fields to `bool` fs/ceph/super.h: convert ceph_cap_snap.writing fields to `bool` fs/ceph: consistently use `u32` for `time_warp_seq` fs/ceph/super: reorder fields to eliminate padding holes fs/ceph: remove i_truncate_mutex, use i_fragtree_mutex for both fs/ceph/super.h: add `const` to helpers fs/ceph/super.h: add helper ceph_in_snap() fs/ceph: use ceph_vino() etc. instead of accessing i_vino directly fs/ceph: remove redundant inode number from ceph_inode_info fs/ceph: remove unused field `ceph_cap.last_used` fs/ceph: convert ceph_cap.queue_release to bool fs/ceph/super: move `ceph_cap.caps_item` into the union fs/ceph/snap: add a kmem_cache for struct ceph_snap_realm fs/ceph/super: reorder struct ceph_snap_realm fields fs/ceph/super: remove redundant field `ceph_snap_realm.parent_ino` fs/ceph/acl.c | 2 +- fs/ceph/addr.c | 23 ++++--- fs/ceph/cache.c | 4 +- fs/ceph/caps.c | 14 ++-- fs/ceph/dir.c | 20 +++--- fs/ceph/export.c | 8 +-- fs/ceph/file.c | 28 ++++---- fs/ceph/inode.c | 38 +++++++---- fs/ceph/mds_client.c | 16 ++--- fs/ceph/mds_client.h | 2 +- fs/ceph/quota.c | 6 +- fs/ceph/snap.c | 17 +++-- fs/ceph/super.c | 9 +++ fs/ceph/super.h | 123 +++++++++++++++++++++++++---------- fs/ceph/util.c | 8 +-- fs/ceph/xattr.c | 18 ++--- include/linux/ceph/ceph_fs.h | 2 +- include/linux/ceph/libceph.h | 1 + 18 files changed, 204 insertions(+), 135 deletions(-) -- 2.47.3