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erofs: use buffered I/O for file-backed mounts by default

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For many use cases (e.g. container images are just fetched from remote),
performance will be impacted if underlay page cache is up-to-date but
direct i/o flushes dirty pages first.

Instead, let's use buffered I/O by default to keep in sync with loop
devices and add a (re)mount option to explicitly give a try to use
direct I/O if supported by the underlying files.

The container startup time is improved as below:
[workload] docker.io/library/workpress:latest
                                     unpack        1st run  non-1st runs
EROFS snapshotter buffered I/O file  4.586404265s  0.308s   0.198s
EROFS snapshotter direct I/O file    4.581742849s  2.238s   0.222s
EROFS snapshotter loop               4.596023152s  0.346s   0.201s
Overlayfs snapshotter                5.382851037s  0.206s   0.214s

Fixes: fb17675026 ("erofs: add file-backed mount support")
Cc: Derek McGowan <derek@mcg.dev>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241212134336.2059899-1-hsiangkao@linux.alibaba.com
This commit is contained in:
Gao Xiang 2024-12-12 21:43:36 +08:00
parent f8d920a402
commit 6422cde1b0
3 changed files with 21 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fs/erofs/fileio.c
View File

@ -9,6 +9,7 @@ struct erofs_fileio_rq {
struct bio_vec bvecs[BIO_MAX_VECS];
struct bio bio;
struct kiocb iocb;
struct super_block *sb;
};
struct erofs_fileio {
@ -52,8 +53,9 @@ static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq)
rq->iocb.ki_pos = rq->bio.bi_iter.bi_sector << SECTOR_SHIFT;
rq->iocb.ki_ioprio = get_current_ioprio();
rq->iocb.ki_complete = erofs_fileio_ki_complete;
rq->iocb.ki_flags = (rq->iocb.ki_filp->f_mode & FMODE_CAN_ODIRECT) ?
IOCB_DIRECT : 0;
if (test_opt(&EROFS_SB(rq->sb)->opt, DIRECT_IO) &&
rq->iocb.ki_filp->f_mode & FMODE_CAN_ODIRECT)
rq->iocb.ki_flags = IOCB_DIRECT;
iov_iter_bvec(&iter, ITER_DEST, rq->bvecs, rq->bio.bi_vcnt,
rq->bio.bi_iter.bi_size);
ret = vfs_iocb_iter_read(rq->iocb.ki_filp, &rq->iocb, &iter);
@ -68,6 +70,7 @@ static struct erofs_fileio_rq *erofs_fileio_rq_alloc(struct erofs_map_dev *mdev)
bio_init(&rq->bio, NULL, rq->bvecs, BIO_MAX_VECS, REQ_OP_READ);
rq->iocb.ki_filp = mdev->m_dif->file;
rq->sb = mdev->m_sb;
return rq;
}

1
fs/erofs/internal.h
View File

@ -176,6 +176,7 @@ struct erofs_sb_info {
#define EROFS_MOUNT_POSIX_ACL 0x00000020
#define EROFS_MOUNT_DAX_ALWAYS 0x00000040
#define EROFS_MOUNT_DAX_NEVER 0x00000080
#define EROFS_MOUNT_DIRECT_IO 0x00000100
#define clear_opt(opt, option) ((opt)->mount_opt &= ~EROFS_MOUNT_##option)
#define set_opt(opt, option) ((opt)->mount_opt |= EROFS_MOUNT_##option)

23
fs/erofs/super.c
View File

@ -364,14 +364,8 @@ static void erofs_default_options(struct erofs_sb_info *sbi)
}
enum {
Opt_user_xattr,
Opt_acl,
Opt_cache_strategy,
Opt_dax,
Opt_dax_enum,
Opt_device,
Opt_fsid,
Opt_domain_id,
Opt_user_xattr, Opt_acl, Opt_cache_strategy, Opt_dax, Opt_dax_enum,
Opt_device, Opt_fsid, Opt_domain_id, Opt_directio,
Opt_err
};
@ -398,6 +392,7 @@ static const struct fs_parameter_spec erofs_fs_parameters[] = {
fsparam_string("device", Opt_device),
fsparam_string("fsid", Opt_fsid),
fsparam_string("domain_id", Opt_domain_id),
fsparam_flag_no("directio", Opt_directio),
{}
};
@ -511,6 +506,16 @@ static int erofs_fc_parse_param(struct fs_context *fc,
errorfc(fc, "%s option not supported", erofs_fs_parameters[opt].name);
break;
#endif
case Opt_directio:
#ifdef CONFIG_EROFS_FS_BACKED_BY_FILE
if (result.boolean)
set_opt(&sbi->opt, DIRECT_IO);
else
clear_opt(&sbi->opt, DIRECT_IO);
#else
errorfc(fc, "%s option not supported", erofs_fs_parameters[opt].name);
#endif
break;
default:
return -ENOPARAM;
}
@ -948,6 +953,8 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root)
seq_puts(seq, ",dax=always");
if (test_opt(opt, DAX_NEVER))
seq_puts(seq, ",dax=never");
if (erofs_is_fileio_mode(sbi) && test_opt(opt, DIRECT_IO))
seq_puts(seq, ",directio");
#ifdef CONFIG_EROFS_FS_ONDEMAND
if (sbi->fsid)
seq_printf(seq, ",fsid=%s", sbi->fsid);