[PATCH RFC 3/4] erofs: introduce page cache share feature
Hongbo Li
lihongbo22 at huawei.com
Thu Jul 25 17:43:31 AEST 2024
On 2024/7/22 14:53, Hongzhen Luo wrote:
> 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
Does this mean the hash is calculated at the file granularity?
> `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;
Why we should cur to pointer the inode? I think we only need to record
the fprt of the content. When we need inode, we can check the
list_empty, and to get the any inode to use.
> + 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))
Not unlock here.
> + 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;
May be we just need compare vi->fprt_hash, no need memcmp?
> +}
> +
> +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))
should call spin_unlock when failed
> + 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;
pcs = ano_inode->i_private;
spin_lock(&ano_inode->i_lock);
if (!pcs) {
xxx
}
spin_unlock(&ano_inode->i_lock);
> + 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,
Does this work on on-demand mode over fscache? As I know, this io path
is only for erofs, not for erofs over fscache.
> +};
> +
> +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
Thanks,
Hongbo
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