[PATCH RFC 3/4] erofs: introduce page cache share feature
Hongzhen Luo
hongzhen at linux.alibaba.com
Mon Jul 22 16:53:53 AEST 2024
Currently, reading files with different paths (or names) but the same
content will consume multiple copies of the page cache, even if the
content of these page caches is the same. For example, reading identical
files (e.g., *.so files) from two different minor versions of container
images will cost multiple copies of the same page cache, since different
containers have different mount points. Therefore, sharing the page cache
for files with the same content can save memory.
This introduces the page cache share feature in erofs. During the mkfs
phase, file content is hashed and the hash value is stored in the
`user.fingerprint` extended attribute. Inodes of files with the same
`user.fingerprint` are mapped to an anonymous inode, whose page cache
stores the actual contents. In this way, a single copy of the anonymous
inode's page cache can serve read requests from several files mapped to it.
Below is the memory usage for reading all files in two different minor
versions of container images:
+-------------------+------------------+-------------+---------------+
| Image | Page Cache Share | Memory (MB) | Memory |
| | | | Reduction (%) |
+-------------------+------------------+-------------+---------------+
| | No | 241 | - |
| redis +------------------+-------------+---------------+
| 7.2.4 & 7.2.5 | Yes | 163 | 33% |
+-------------------+------------------+-------------+---------------+
| | No | 872 | - |
| postgres +------------------+-------------+---------------+
| 16.1 & 16.2 | Yes | 630 | 28% |
+-------------------+------------------+-------------+---------------+
| | No | 2771 | - |
| tensorflow +------------------+-------------+---------------+
| 1.11.0 & 2.11.1 | Yes | 2340 | 16% |
+-------------------+------------------+-------------+---------------+
| | No | 926 | - |
| mysql +------------------+-------------+---------------+
| 8.0.11 & 8.0.12 | Yes | 735 | 21% |
+-------------------+------------------+-------------+---------------+
| | No | 390 | - |
| nginx +------------------+-------------+---------------+
| 7.2.4 & 7.2.5 | Yes | 219 | 44% |
+-------------------+------------------+-------------+---------------+
| tomcat | No | 924 | - |
| 10.1.25 & 10.1.26 +------------------+-------------+---------------+
| | Yes | 474 | 49% |
+-------------------+------------------+-------------+---------------+
Additionally, the table below shows the runtime memory usage of the
container:
+-------------------+------------------+-------------+---------------+
| Image | Page Cache Share | Memory (MB) | Memory |
| | | | Reduction (%) |
+-------------------+------------------+-------------+---------------+
| | No | 34.9 | - |
| redis +------------------+-------------+---------------+
| 7.2.4 & 7.2.5 | Yes | 33.6 | 4% |
+-------------------+------------------+-------------+---------------+
| | No | 149.1 | - |
| postgres +------------------+-------------+---------------+
| 16.1 & 16.2 | Yes | 95 | 37% |
+-------------------+------------------+-------------+---------------+
| | No | 1027.9 | - |
| tensorflow +------------------+-------------+---------------+
| 1.11.0 & 2.11.1 | Yes | 934.3 | 10% |
+-------------------+------------------+-------------+---------------+
| | No | 155.0 | - |
| mysql +------------------+-------------+---------------+
| 8.0.11 & 8.0.12 | Yes | 139.1 | 11% |
+-------------------+------------------+-------------+---------------+
| | No | 25.4 | - |
| nginx +------------------+-------------+---------------+
| 7.2.4 & 7.2.5 | Yes | 18.8 | 26% |
+-------------------+------------------+-------------+---------------+
| tomcat | No | 186 | - |
| 10.1.25 & 10.1.26 +------------------+-------------+---------------+
| | Yes | 99 | 47% |
+-------------------+------------------+-------------+---------------+
Signed-off-by: Hongzhen Luo <hongzhen at linux.alibaba.com>
---
fs/erofs/Kconfig | 10 ++
fs/erofs/Makefile | 1 +
fs/erofs/internal.h | 8 +
fs/erofs/pagecache_share.c | 313 +++++++++++++++++++++++++++++++++++++
fs/erofs/pagecache_share.h | 20 +++
5 files changed, 352 insertions(+)
create mode 100644 fs/erofs/pagecache_share.c
create mode 100644 fs/erofs/pagecache_share.h
diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
index 7dcdce660cac..756a74de623c 100644
--- a/fs/erofs/Kconfig
+++ b/fs/erofs/Kconfig
@@ -158,3 +158,13 @@ config EROFS_FS_PCPU_KTHREAD_HIPRI
at higher priority.
If unsure, say N.
+
+config EROFS_FS_PAGE_CACHE_SHARE
+ bool "EROFS page cache share support"
+ depends on EROFS_FS
+ default n
+ help
+ This permits EROFS to share page cache for files with same
+ fingerprints.
+
+ If unsure, say N.
diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
index 097d672e6b14..f14a2ac0e561 100644
--- a/fs/erofs/Makefile
+++ b/fs/erofs/Makefile
@@ -8,3 +8,4 @@ erofs-$(CONFIG_EROFS_FS_ZIP_LZMA) += decompressor_lzma.o
erofs-$(CONFIG_EROFS_FS_ZIP_DEFLATE) += decompressor_deflate.o
erofs-$(CONFIG_EROFS_FS_ZIP_ZSTD) += decompressor_zstd.o
erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o
+erofs-$(CONFIG_EROFS_FS_PAGE_CACHE_SHARE) += pagecache_share.o
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 2c695ec6ee71..136d6bed417b 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -288,6 +288,12 @@ struct erofs_inode {
};
#endif /* CONFIG_EROFS_FS_ZIP */
};
+#ifdef CONFIG_EROFS_FS_PAGE_CACHE_SHARE
+ struct list_head pcs_list;
+ char *fprt;
+ int fprt_len;
+ unsigned long fprt_hash;
+#endif
/* the corresponding vfs inode */
struct inode vfs_inode;
};
@@ -376,6 +382,7 @@ extern const struct super_operations erofs_sops;
extern const struct address_space_operations erofs_raw_access_aops;
extern const struct address_space_operations z_erofs_aops;
extern const struct address_space_operations erofs_fscache_access_aops;
+extern const struct address_space_operations erofs_pcs_aops;
extern const struct inode_operations erofs_generic_iops;
extern const struct inode_operations erofs_symlink_iops;
@@ -384,6 +391,7 @@ extern const struct inode_operations erofs_dir_iops;
extern const struct file_operations erofs_file_fops;
extern const struct file_operations erofs_dir_fops;
+extern const struct file_operations erofs_pcs_file_fops;
extern const struct iomap_ops z_erofs_iomap_report_ops;
diff --git a/fs/erofs/pagecache_share.c b/fs/erofs/pagecache_share.c
new file mode 100644
index 000000000000..e8c8fe16cda5
--- /dev/null
+++ b/fs/erofs/pagecache_share.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024, Alibaba Cloud
+ */
+#include <linux/xxhash.h>
+#include "pagecache_share.h"
+#include "internal.h"
+#include "xattr.h"
+
+#define PCS_FPRT_IDX 1
+#define PCS_FPRT_NAME "fingerprint"
+#define PCS_FPRT_MAXLEN 1024
+
+struct erofs_pcs {
+ struct erofs_inode *cur;
+ struct rw_semaphore rw_sem;
+ struct mutex list_mutex;
+ struct list_head list;
+};
+
+static DEFINE_MUTEX(pseudo_mnt_lock);
+static unsigned long pseudo_mnt_count;
+static struct vfsmount *erofs_pcs_mnt;
+
+int erofs_pcs_init_mnt(void)
+{
+ mutex_lock(&pseudo_mnt_lock);
+ if (!erofs_pcs_mnt) {
+ erofs_pcs_mnt = kern_mount(&erofs_anon_fs_type);
+ if (IS_ERR(erofs_pcs_mnt))
+ return PTR_ERR(erofs_pcs_mnt);
+ pseudo_mnt_count = 1;
+ } else
+ pseudo_mnt_count += 1;
+ mutex_unlock(&pseudo_mnt_lock);
+ return 0;
+}
+
+int erofs_pcs_free_mnt(void)
+{
+ mutex_lock(&pseudo_mnt_lock);
+ pseudo_mnt_count -= 1;
+ if (pseudo_mnt_count < 0)
+ return -EINVAL;
+ if (pseudo_mnt_count == 0) {
+ kern_unmount(erofs_pcs_mnt);
+ erofs_pcs_mnt = NULL;
+ }
+ mutex_unlock(&pseudo_mnt_lock);
+ return 0;
+}
+
+void erofs_pcs_fill_inode(struct inode *inode)
+{
+ struct erofs_inode *vi = EROFS_I(inode);
+ char fprt[PCS_FPRT_MAXLEN];
+
+ vi->fprt_len = erofs_getxattr(inode, PCS_FPRT_IDX, PCS_FPRT_NAME, fprt,
+ PCS_FPRT_MAXLEN);
+ if (vi->fprt_len > 0 && vi->fprt_len <= PCS_FPRT_MAXLEN) {
+ vi->fprt = kmalloc(vi->fprt_len, GFP_KERNEL);
+ if (IS_ERR(vi->fprt)) {
+ vi->fprt_len = -1;
+ return;
+ }
+ memcpy(vi->fprt, fprt, vi->fprt_len);
+ vi->fprt_hash = xxh32(vi->fprt, vi->fprt_len, 0);
+ }
+}
+
+static int erofs_pcs_eq(struct inode *ano_inode, void *data)
+{
+ struct erofs_pcs *pcs = ano_inode->i_private;
+ struct erofs_inode *vi = (struct erofs_inode *)data;
+
+ return pcs && pcs->cur && pcs->cur->fprt_len == vi->fprt_len &&
+ memcmp(pcs->cur->fprt, vi->fprt, vi->fprt_len) == 0 ? 1 : 0;
+}
+
+static int erofs_pcs_set_aops(struct inode *ano_inode, void *data)
+{
+ ano_inode->i_mapping->a_ops = &erofs_pcs_aops;
+ ano_inode->i_size = ((struct erofs_inode *)data)->vfs_inode.i_size;
+ return 0;
+}
+
+int erofs_pcs_add(struct inode *inode)
+{
+ struct erofs_inode *vi = EROFS_I(inode);
+ struct inode *ano_inode;
+ struct erofs_pcs *pcs;
+
+ ano_inode = iget5_locked(erofs_pcs_mnt->mnt_sb, vi->fprt_hash,
+ erofs_pcs_eq, erofs_pcs_set_aops, vi);
+ spin_lock(&ano_inode->i_lock);
+ if (!ano_inode->i_private) {
+ pcs = kzalloc(sizeof(struct erofs_pcs), GFP_KERNEL);
+ if (IS_ERR(pcs))
+ return -ENOMEM;
+ INIT_LIST_HEAD(&pcs->list);
+ mutex_init(&pcs->list_mutex);
+ init_rwsem(&pcs->rw_sem);
+ ano_inode->i_private = pcs;
+ }
+ spin_unlock(&ano_inode->i_lock);
+ pcs = ano_inode->i_private;
+ mutex_lock(&pcs->list_mutex);
+ list_add_tail(&vi->pcs_list, &pcs->list);
+ if (!pcs->cur) {
+ pcs->cur = list_first_entry(&pcs->list,
+ struct erofs_inode, pcs_list);
+ }
+ mutex_unlock(&pcs->list_mutex);
+ if (ano_inode->i_state & I_NEW)
+ unlock_new_inode(ano_inode);
+ return 0;
+}
+
+int erofs_pcs_remove(struct inode *inode)
+{
+ struct erofs_inode *vi = EROFS_I(inode), *p, *tmp;
+ struct inode *ano_inode;
+ struct erofs_pcs *pcs;
+
+ ano_inode = iget5_locked(erofs_pcs_mnt->mnt_sb, vi->fprt_hash,
+ erofs_pcs_eq, erofs_pcs_set_aops, vi);
+ iput(ano_inode);
+ pcs = ano_inode->i_private;
+ if (!pcs)
+ return -EINVAL;
+ mutex_lock(&pcs->list_mutex);
+ if (vi == pcs->cur) {
+ /* synchronize with reads using pcs->cur */
+ down_write(&pcs->rw_sem);
+ list_del(&pcs->cur->pcs_list);
+ if (list_empty(&pcs->list)) {
+ pcs->cur = NULL;
+ up_write(&pcs->rw_sem);
+ goto free_ano_inode;
+ }
+ pcs->cur = list_first_entry(&pcs->list, struct erofs_inode,
+ pcs_list);
+ up_write(&pcs->rw_sem);
+ } else {
+ list_for_each_entry_safe(p, tmp, &pcs->list, pcs_list) {
+ if (p == vi) {
+ list_del(&p->pcs_list);
+ break;
+ }
+ }
+ }
+ iput(ano_inode);
+ mutex_unlock(&pcs->list_mutex);
+ return 0;
+
+free_ano_inode:
+ mutex_unlock(&pcs->list_mutex);
+ spin_lock(&ano_inode->i_lock);
+ if (atomic_read(&ano_inode->i_count) == 1) {
+ ano_inode->i_private = NULL;
+ kfree(pcs);
+ }
+ spin_unlock(&ano_inode->i_lock);
+ iput(ano_inode);
+ return 0;
+}
+
+static int erofs_pcs_iomap_begin(struct inode *ano_inode, loff_t offset,
+ loff_t length, unsigned int flags,
+ struct iomap *iomap, struct iomap *srcmap)
+{
+ struct erofs_pcs *pcs;
+
+ pcs = ano_inode->i_private;
+ if (!pcs || !pcs->cur)
+ return -EINVAL;
+
+ return erofs_iomap_begin(&pcs->cur->vfs_inode, offset, length, flags,
+ iomap, srcmap);
+}
+
+static int erofs_pcs_iomap_end(struct inode *ano_inode, loff_t pos,
+ loff_t length, ssize_t written,
+ unsigned int flags, struct iomap *iomap)
+{
+ struct erofs_pcs *pcs;
+
+ pcs = ano_inode->i_private;
+ if (!pcs)
+ return -EINVAL;
+
+ return erofs_iomap_end(&pcs->cur->vfs_inode, pos, length, written,
+ flags, iomap);
+}
+
+const struct iomap_ops erofs_pcs_iomap_ops = {
+ .iomap_begin = erofs_pcs_iomap_begin,
+ .iomap_end = erofs_pcs_iomap_end,
+};
+
+static int erofs_pcs_read_folio(struct file *file, struct folio *folio)
+{
+ int err;
+ struct erofs_pcs *pcs;
+
+ pcs = file->f_inode->i_private;
+ if (!pcs)
+ return -EINVAL;
+ down_read(&pcs->rw_sem);
+ err = iomap_read_folio(folio, &erofs_pcs_iomap_ops);
+ up_read(&pcs->rw_sem);
+ return err;
+}
+
+static void erofs_pcs_readahead(struct readahead_control *rac)
+{
+ struct erofs_pcs *pcs;
+
+ pcs = rac->file->f_inode->i_private;
+ if (!pcs)
+ return;
+ down_read(&pcs->rw_sem);
+ iomap_readahead(rac, &erofs_pcs_iomap_ops);
+ up_read(&pcs->rw_sem);
+}
+
+const struct address_space_operations erofs_pcs_aops = {
+ .read_folio = erofs_pcs_read_folio,
+ .readahead = erofs_pcs_readahead,
+};
+
+static struct file *erofs_pcs_alloc_file(struct file *file,
+ struct inode *ano_inode)
+{
+ struct file *ano_file;
+
+ ano_file = alloc_file_pseudo(ano_inode, erofs_pcs_mnt, "[erofs_pcs_f]",
+ O_RDONLY, &erofs_file_fops);
+ file_ra_state_init(&ano_file->f_ra, file->f_mapping);
+ return ano_file;
+}
+
+static int erofs_pcs_file_open(struct inode *inode, struct file *file)
+{
+ struct file *ano_file;
+ struct inode *ano_inode;
+ struct erofs_inode *vi = EROFS_I(inode);
+
+ ano_inode = iget5_locked(erofs_pcs_mnt->mnt_sb, vi->fprt_hash,
+ erofs_pcs_eq, erofs_pcs_set_aops, vi);
+ if (!ano_inode)
+ return -EINVAL;
+ ano_file = erofs_pcs_alloc_file(file, ano_inode);
+ file->private_data = (void *)ano_file;
+ return 0;
+}
+
+static int erofs_pcs_file_release(struct inode *inode, struct file *file)
+{
+ if (!file->private_data)
+ return -EINVAL;
+ fput((struct file *)file->private_data);
+ file->private_data = NULL;
+ return 0;
+}
+
+static ssize_t erofs_pcs_file_read_iter(struct kiocb *iocb,
+ struct iov_iter *to)
+{
+ struct file *file, *ano_file;
+ struct kiocb ano_iocb;
+ ssize_t res;
+
+ memcpy(&ano_iocb, iocb, sizeof(struct kiocb));
+ file = iocb->ki_filp;
+ ano_file = file->private_data;
+ if (!ano_file)
+ return -EINVAL;
+ ano_iocb.ki_filp = ano_file;
+ res = filemap_read(&ano_iocb, to, 0);
+ memcpy(iocb, &ano_iocb, sizeof(struct kiocb));
+ iocb->ki_filp = file;
+ file_accessed(file);
+ return res;
+}
+
+static vm_fault_t erofs_pcs_fault(struct vm_fault *vmf)
+{
+ return filemap_fault(vmf);
+}
+
+static const struct vm_operations_struct erofs_pcs_file_vm_ops = {
+ .fault = erofs_pcs_fault,
+};
+
+static int erofs_pcs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct file *ano_file = file->private_data;
+
+ vma_set_file(vma, ano_file);
+ vma->vm_ops = &erofs_pcs_file_vm_ops;
+ return 0;
+}
+
+const struct file_operations erofs_pcs_file_fops = {
+ .open = erofs_pcs_file_open,
+ .llseek = generic_file_llseek,
+ .read_iter = erofs_pcs_file_read_iter,
+ .mmap = erofs_pcs_mmap,
+ .release = erofs_pcs_file_release,
+ .get_unmapped_area = thp_get_unmapped_area,
+ .splice_read = filemap_splice_read,
+};
diff --git a/fs/erofs/pagecache_share.h b/fs/erofs/pagecache_share.h
new file mode 100644
index 000000000000..a7affb0382bd
--- /dev/null
+++ b/fs/erofs/pagecache_share.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2024, Alibaba Cloud
+ */
+#ifndef __EROFS_PAGECACHE_SHARE_H
+#define __EROFS_PAGECACHE_SHARE_H
+
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/rwlock.h>
+#include <linux/mutex.h>
+#include "internal.h"
+
+int erofs_pcs_init_mnt(void);
+int erofs_pcs_free_mnt(void);
+void erofs_pcs_fill_inode(struct inode *inode);
+int erofs_pcs_add(struct inode *inode);
+int erofs_pcs_remove(struct inode *inode);
+
+#endif
--
2.43.5
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