* [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir()
@ 2025-07-14 9:39 Chao Yu
2025-07-17 8:26 ` Gao Xiang
0 siblings, 1 reply; 4+ messages in thread
From: Chao Yu @ 2025-07-14 9:39 UTC (permalink / raw)
To: xiang
Cc: linux-erofs, linux-kernel, Yue Hu, Jeffle Xu, Sandeep Dhavale,
Hongbo Li, Chao Yu
This patch supports to readahead more blocks in erofs_readdir(), it can
enhance readdir performance in large direcotry.
readdir test in a large directory which contains 12000 sub-files.
files_per_second
Before: 926385.54
After: 2380435.562
Meanwhile, let's introduces a new sysfs entry to control readahead
bytes to provide more flexible policy for readahead of readdir().
- location: /sys/fs/erofs/<disk>/dir_ra_bytes
- default value: 16384
- disable readahead: set the value to 0
Signed-off-by: Chao Yu <chao@kernel.org>
---
v3:
- add EROFS prefix for macro
- update new sysfs interface to 1) use bytes instead of pages
2) remove upper boundary limitation
- fix bug of pageidx calculation
Documentation/ABI/testing/sysfs-fs-erofs | 8 ++++++++
fs/erofs/dir.c | 13 +++++++++++++
fs/erofs/internal.h | 4 ++++
fs/erofs/super.c | 2 ++
fs/erofs/sysfs.c | 2 ++
5 files changed, 29 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
index bf3b6299c15e..85fa56ca092c 100644
--- a/Documentation/ABI/testing/sysfs-fs-erofs
+++ b/Documentation/ABI/testing/sysfs-fs-erofs
@@ -35,3 +35,11 @@ Description: Used to set or show hardware accelerators in effect
and multiple accelerators are separated by '\n'.
Supported accelerator(s): qat_deflate.
Disable all accelerators with an empty string (echo > accel).
+
+What: /sys/fs/erofs/<disk>/dir_ra_bytes
+Date: July 2025
+Contact: "Chao Yu" <chao@kernel.org>
+Description: Used to set or show readahead bytes during readdir(), by
+ default the value is 16384.
+
+ - 0: disable readahead.
diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
index 3e4b38bec0aa..950d6b0046f4 100644
--- a/fs/erofs/dir.c
+++ b/fs/erofs/dir.c
@@ -47,8 +47,10 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
struct inode *dir = file_inode(f);
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
struct super_block *sb = dir->i_sb;
+ struct file_ra_state *ra = &f->f_ra;
unsigned long bsz = sb->s_blocksize;
unsigned int ofs = erofs_blkoff(sb, ctx->pos);
+ unsigned long nr_pages = DIV_ROUND_UP_POW2(dir->i_size, PAGE_SIZE);
int err = 0;
bool initial = true;
@@ -63,6 +65,17 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
break;
}
+ /* readahead blocks to enhance performance in large directory */
+ if (EROFS_I_SB(dir)->dir_ra_bytes) {
+ unsigned long idx = DIV_ROUND_UP(ctx->pos, PAGE_SIZE);
+ pgoff_t ra_pages = DIV_ROUND_UP(
+ EROFS_I_SB(dir)->dir_ra_bytes, PAGE_SIZE);
+
+ if (nr_pages - idx > 1 && !ra_has_index(ra, idx))
+ page_cache_sync_readahead(dir->i_mapping, ra,
+ f, idx, min(nr_pages - idx, ra_pages));
+ }
+
de = erofs_bread(&buf, dbstart, true);
if (IS_ERR(de)) {
erofs_err(sb, "failed to readdir of logical block %llu of nid %llu",
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 0d19bde8c094..4399b9332307 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -157,6 +157,7 @@ struct erofs_sb_info {
/* sysfs support */
struct kobject s_kobj; /* /sys/fs/erofs/<devname> */
struct completion s_kobj_unregister;
+ erofs_off_t dir_ra_bytes;
/* fscache support */
struct fscache_volume *volume;
@@ -238,6 +239,9 @@ EROFS_FEATURE_FUNCS(xattr_filter, compat, COMPAT_XATTR_FILTER)
#define EROFS_I_BL_XATTR_BIT (BITS_PER_LONG - 1)
#define EROFS_I_BL_Z_BIT (BITS_PER_LONG - 2)
+/* default readahead size of directory */
+#define EROFS_DIR_RA_BYTES 16384
+
struct erofs_inode {
erofs_nid_t nid;
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index e1e9f06e8342..38fc4813a896 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -715,6 +715,8 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
if (err)
return err;
+ sbi->dir_ra_bytes = EROFS_DIR_RA_BYTES;
+
erofs_info(sb, "mounted with root inode @ nid %llu.", sbi->root_nid);
return 0;
}
diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index eed8797a193f..9d9f820a5621 100644
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -65,12 +65,14 @@ EROFS_ATTR_FUNC(drop_caches, 0200);
#ifdef CONFIG_EROFS_FS_ZIP_ACCEL
EROFS_ATTR_FUNC(accel, 0644);
#endif
+EROFS_ATTR_RW_UI(dir_ra_bytes, erofs_sb_info);
static struct attribute *erofs_sb_attrs[] = {
#ifdef CONFIG_EROFS_FS_ZIP
ATTR_LIST(sync_decompress),
ATTR_LIST(drop_caches),
#endif
+ ATTR_LIST(dir_ra_bytes),
NULL,
};
ATTRIBUTE_GROUPS(erofs_sb);
--
2.49.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir()
2025-07-14 9:39 [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir() Chao Yu
@ 2025-07-17 8:26 ` Gao Xiang
2025-07-18 1:52 ` Chao Yu
0 siblings, 1 reply; 4+ messages in thread
From: Gao Xiang @ 2025-07-17 8:26 UTC (permalink / raw)
To: Chao Yu, xiang
Cc: linux-erofs, linux-kernel, Yue Hu, Jeffle Xu, Sandeep Dhavale,
Hongbo Li
Hi Chao,
On 2025/7/14 17:39, Chao Yu wrote:
> This patch supports to readahead more blocks in erofs_readdir(), it can
> enhance readdir performance in large direcotry.
>
> readdir test in a large directory which contains 12000 sub-files.
>
> files_per_second
> Before: 926385.54
> After: 2380435.562
>
> Meanwhile, let's introduces a new sysfs entry to control readahead
> bytes to provide more flexible policy for readahead of readdir().
> - location: /sys/fs/erofs/<disk>/dir_ra_bytes
> - default value: 16384
> - disable readahead: set the value to 0
>
> Signed-off-by: Chao Yu <chao@kernel.org>
> ---
> v3:
> - add EROFS prefix for macro
> - update new sysfs interface to 1) use bytes instead of pages
> 2) remove upper boundary limitation
> - fix bug of pageidx calculation
> Documentation/ABI/testing/sysfs-fs-erofs | 8 ++++++++
> fs/erofs/dir.c | 13 +++++++++++++
> fs/erofs/internal.h | 4 ++++
> fs/erofs/super.c | 2 ++
> fs/erofs/sysfs.c | 2 ++
> 5 files changed, 29 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ABI/testing/sysfs-fs-erofs
> index bf3b6299c15e..85fa56ca092c 100644
> --- a/Documentation/ABI/testing/sysfs-fs-erofs
> +++ b/Documentation/ABI/testing/sysfs-fs-erofs
> @@ -35,3 +35,11 @@ Description: Used to set or show hardware accelerators in effect
> and multiple accelerators are separated by '\n'.
> Supported accelerator(s): qat_deflate.
> Disable all accelerators with an empty string (echo > accel).
> +
> +What: /sys/fs/erofs/<disk>/dir_ra_bytes
> +Date: July 2025
> +Contact: "Chao Yu" <chao@kernel.org>
> +Description: Used to set or show readahead bytes during readdir(), by
> + default the value is 16384.
> +
> + - 0: disable readahead.
> diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
> index 3e4b38bec0aa..950d6b0046f4 100644
> --- a/fs/erofs/dir.c
> +++ b/fs/erofs/dir.c
> @@ -47,8 +47,10 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
> struct inode *dir = file_inode(f);
> struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
> struct super_block *sb = dir->i_sb;
> + struct file_ra_state *ra = &f->f_ra;
> unsigned long bsz = sb->s_blocksize;
> unsigned int ofs = erofs_blkoff(sb, ctx->pos);
> + unsigned long nr_pages = DIV_ROUND_UP_POW2(dir->i_size, PAGE_SIZE);
pgoff_t ra_pages = PAGE_ALIGN(EROFS_SB(dir)->dir_ra_bytes);
> int err = 0;
> bool initial = true;
>
> @@ -63,6 +65,17 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
> break;
> }
>
> + /* readahead blocks to enhance performance in large directory */
> + if (EROFS_I_SB(dir)->dir_ra_bytes) {
if (ra_pages) {
> + unsigned long idx = DIV_ROUND_UP(ctx->pos, PAGE_SIZE);
> + pgoff_t ra_pages = DIV_ROUND_UP(
> + EROFS_I_SB(dir)->dir_ra_bytes, PAGE_SIZE);
pgoff_t idx = PAGE_ALIGN(ctx->pos);
pgoff_t pages = min(nr_pages - idx, ra_pages);
> +
> + if (nr_pages - idx > 1 && !ra_has_index(ra, idx))
if (pages > 1 && !ra_has_index(ra, idx))
page_cache_sync_readahead(dir->i_mapping, ra,
f, idx, pages)?
> + page_cache_sync_readahead(dir->i_mapping, ra,
> + f, idx, min(nr_pages - idx, ra_pages));
> + }
> +
> de = erofs_bread(&buf, dbstart, true);
> if (IS_ERR(de)) {
> erofs_err(sb, "failed to readdir of logical block %llu of nid %llu",
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 0d19bde8c094..4399b9332307 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -157,6 +157,7 @@ struct erofs_sb_info {
> /* sysfs support */
> struct kobject s_kobj; /* /sys/fs/erofs/<devname> */
> struct completion s_kobj_unregister;
> + erofs_off_t dir_ra_bytes;
>
> /* fscache support */
> struct fscache_volume *volume;
> @@ -238,6 +239,9 @@ EROFS_FEATURE_FUNCS(xattr_filter, compat, COMPAT_XATTR_FILTER)
> #define EROFS_I_BL_XATTR_BIT (BITS_PER_LONG - 1)
> #define EROFS_I_BL_Z_BIT (BITS_PER_LONG - 2)
>
> +/* default readahead size of directory */
/* default readahead size of directories */
Otherwise it looks good to me.
Thanks,
Gao Xiang
> +#define EROFS_DIR_RA_BYTES 16384
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir()
2025-07-17 8:26 ` Gao Xiang
@ 2025-07-18 1:52 ` Chao Yu
2025-07-18 2:45 ` Gao Xiang
0 siblings, 1 reply; 4+ messages in thread
From: Chao Yu @ 2025-07-18 1:52 UTC (permalink / raw)
To: Gao Xiang, xiang
Cc: chao, linux-erofs, linux-kernel, Yue Hu, Jeffle Xu,
Sandeep Dhavale, Hongbo Li
Hi Xiang,
On 2025/7/17 16:26, Gao Xiang wrote:
> Hi Chao,
>
> On 2025/7/14 17:39, Chao Yu wrote:
>> This patch supports to readahead more blocks in erofs_readdir(), it can
>> enhance readdir performance in large direcotry.
>>
>> readdir test in a large directory which contains 12000 sub-files.
>>
>> files_per_second
>> Before: 926385.54
>> After: 2380435.562
>>
>> Meanwhile, let's introduces a new sysfs entry to control readahead
>> bytes to provide more flexible policy for readahead of readdir().
>> - location: /sys/fs/erofs/<disk>/dir_ra_bytes
>> - default value: 16384
>> - disable readahead: set the value to 0
>>
>> Signed-off-by: Chao Yu <chao@kernel.org>
>> ---
>> v3:
>> - add EROFS prefix for macro
>> - update new sysfs interface to 1) use bytes instead of pages
>> 2) remove upper boundary limitation
>> - fix bug of pageidx calculation
>> Documentation/ABI/testing/sysfs-fs-erofs | 8 ++++++++
>> fs/erofs/dir.c | 13 +++++++++++++
>> fs/erofs/internal.h | 4 ++++
>> fs/erofs/super.c | 2 ++
>> fs/erofs/sysfs.c | 2 ++
>> 5 files changed, 29 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/
>> ABI/testing/sysfs-fs-erofs
>> index bf3b6299c15e..85fa56ca092c 100644
>> --- a/Documentation/ABI/testing/sysfs-fs-erofs
>> +++ b/Documentation/ABI/testing/sysfs-fs-erofs
>> @@ -35,3 +35,11 @@ Description: Used to set or show hardware
>> accelerators in effect
>> and multiple accelerators are separated by '\n'.
>> Supported accelerator(s): qat_deflate.
>> Disable all accelerators with an empty string (echo > accel).
>> +
>> +What: /sys/fs/erofs/<disk>/dir_ra_bytes
>> +Date: July 2025
>> +Contact: "Chao Yu" <chao@kernel.org>
>> +Description: Used to set or show readahead bytes during readdir(), by
>> + default the value is 16384.
>> +
>> + - 0: disable readahead.
>> diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
>> index 3e4b38bec0aa..950d6b0046f4 100644
>> --- a/fs/erofs/dir.c
>> +++ b/fs/erofs/dir.c
>> @@ -47,8 +47,10 @@ static int erofs_readdir(struct file *f, struct
>> dir_context *ctx)
>> struct inode *dir = file_inode(f);
>> struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
>> struct super_block *sb = dir->i_sb;
>> + struct file_ra_state *ra = &f->f_ra;
>> unsigned long bsz = sb->s_blocksize;
>> unsigned int ofs = erofs_blkoff(sb, ctx->pos);
>> + unsigned long nr_pages = DIV_ROUND_UP_POW2(dir->i_size, PAGE_SIZE);
>
> pgoff_t ra_pages = PAGE_ALIGN(EROFS_SB(dir)->dir_ra_bytes);
Do you mean?
pgoff_t ra_pages = PAGE_ALIGN(EROFS_SB(dir)->dir_ra_bytes) >> PAGE_SHIFT?
>
>> int err = 0;
>> bool initial = true;
>> @@ -63,6 +65,17 @@ static int erofs_readdir(struct file *f, struct
>> dir_context *ctx)
>> break;
>> }
>> + /* readahead blocks to enhance performance in large directory */
>> + if (EROFS_I_SB(dir)->dir_ra_bytes) {
> > if (ra_pages) {
>
>> + unsigned long idx = DIV_ROUND_UP(ctx->pos, PAGE_SIZE);
>> + pgoff_t ra_pages = DIV_ROUND_UP(
>> + EROFS_I_SB(dir)->dir_ra_bytes, PAGE_SIZE);
I put calculation here because if the value is zero, we don't need
unnecessary calculation above, anyway, will update as you suggested, but
let me know if you have any other concerns. :)
>
> pgoff_t idx = PAGE_ALIGN(ctx->pos);
Ditto,
Thanks,
> pgoff_t pages = min(nr_pages - idx, ra_pages);
>
>> +
>> + if (nr_pages - idx > 1 && !ra_has_index(ra, idx))
>
> if (pages > 1 && !ra_has_index(ra, idx))
> page_cache_sync_readahead(dir->i_mapping, ra,
> f, idx, pages)?
>
>
>> + page_cache_sync_readahead(dir->i_mapping, ra,
>> + f, idx, min(nr_pages - idx, ra_pages));
>> + }
>> +
>> de = erofs_bread(&buf, dbstart, true);
>> if (IS_ERR(de)) {
>> erofs_err(sb, "failed to readdir of logical block %llu
>> of nid %llu",
>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
>> index 0d19bde8c094..4399b9332307 100644
>> --- a/fs/erofs/internal.h
>> +++ b/fs/erofs/internal.h
>> @@ -157,6 +157,7 @@ struct erofs_sb_info {
>> /* sysfs support */
>> struct kobject s_kobj; /* /sys/fs/erofs/<devname> */
>> struct completion s_kobj_unregister;
>> + erofs_off_t dir_ra_bytes;
>> /* fscache support */
>> struct fscache_volume *volume;
>> @@ -238,6 +239,9 @@ EROFS_FEATURE_FUNCS(xattr_filter, compat,
>> COMPAT_XATTR_FILTER)
>> #define EROFS_I_BL_XATTR_BIT (BITS_PER_LONG - 1)
>> #define EROFS_I_BL_Z_BIT (BITS_PER_LONG - 2)
>> +/* default readahead size of directory */
>
> /* default readahead size of directories */
>
> Otherwise it looks good to me.
>
> Thanks,
> Gao Xiang
>
>> +#define EROFS_DIR_RA_BYTES 16384
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir()
2025-07-18 1:52 ` Chao Yu
@ 2025-07-18 2:45 ` Gao Xiang
0 siblings, 0 replies; 4+ messages in thread
From: Gao Xiang @ 2025-07-18 2:45 UTC (permalink / raw)
To: Chao Yu, xiang
Cc: linux-erofs, linux-kernel, Yue Hu, Jeffle Xu, Sandeep Dhavale,
Hongbo Li
On 2025/7/18 09:52, Chao Yu wrote:
> Hi Xiang,
>
> On 2025/7/17 16:26, Gao Xiang wrote:
>> Hi Chao,
>>
>> On 2025/7/14 17:39, Chao Yu wrote:
>>> This patch supports to readahead more blocks in erofs_readdir(), it can
>>> enhance readdir performance in large direcotry.
>>>
>>> readdir test in a large directory which contains 12000 sub-files.
>>>
>>> files_per_second
>>> Before: 926385.54
>>> After: 2380435.562
>>>
>>> Meanwhile, let's introduces a new sysfs entry to control readahead
>>> bytes to provide more flexible policy for readahead of readdir().
>>> - location: /sys/fs/erofs/<disk>/dir_ra_bytes
>>> - default value: 16384
>>> - disable readahead: set the value to 0
>>>
>>> Signed-off-by: Chao Yu <chao@kernel.org>
>>> ---
>>> v3:
>>> - add EROFS prefix for macro
>>> - update new sysfs interface to 1) use bytes instead of pages
>>> 2) remove upper boundary limitation
>>> - fix bug of pageidx calculation
>>> Documentation/ABI/testing/sysfs-fs-erofs | 8 ++++++++
>>> fs/erofs/dir.c | 13 +++++++++++++
>>> fs/erofs/internal.h | 4 ++++
>>> fs/erofs/super.c | 2 ++
>>> fs/erofs/sysfs.c | 2 ++
>>> 5 files changed, 29 insertions(+)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-fs-erofs b/Documentation/ ABI/testing/sysfs-fs-erofs
>>> index bf3b6299c15e..85fa56ca092c 100644
>>> --- a/Documentation/ABI/testing/sysfs-fs-erofs
>>> +++ b/Documentation/ABI/testing/sysfs-fs-erofs
>>> @@ -35,3 +35,11 @@ Description: Used to set or show hardware accelerators in effect
>>> and multiple accelerators are separated by '\n'.
>>> Supported accelerator(s): qat_deflate.
>>> Disable all accelerators with an empty string (echo > accel).
>>> +
>>> +What: /sys/fs/erofs/<disk>/dir_ra_bytes
>>> +Date: July 2025
>>> +Contact: "Chao Yu" <chao@kernel.org>
>>> +Description: Used to set or show readahead bytes during readdir(), by
>>> + default the value is 16384.
>>> +
>>> + - 0: disable readahead.
>>> diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
>>> index 3e4b38bec0aa..950d6b0046f4 100644
>>> --- a/fs/erofs/dir.c
>>> +++ b/fs/erofs/dir.c
>>> @@ -47,8 +47,10 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
>>> struct inode *dir = file_inode(f);
>>> struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
>>> struct super_block *sb = dir->i_sb;
>>> + struct file_ra_state *ra = &f->f_ra;
>>> unsigned long bsz = sb->s_blocksize;
>>> unsigned int ofs = erofs_blkoff(sb, ctx->pos);
>>> + unsigned long nr_pages = DIV_ROUND_UP_POW2(dir->i_size, PAGE_SIZE);
>>
>> pgoff_t ra_pages = PAGE_ALIGN(EROFS_SB(dir)->dir_ra_bytes);
>
> Do you mean?
>
> pgoff_t ra_pages = PAGE_ALIGN(EROFS_SB(dir)->dir_ra_bytes) >> PAGE_SHIFT?
That seems more complicated, sigh, I think the original
DIV_ROUND_UP_POW2() is better.
>
>>
>>> int err = 0;
>>> bool initial = true;
>>> @@ -63,6 +65,17 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
>>> break;
>>> }
>>> + /* readahead blocks to enhance performance in large directory */
>>> + if (EROFS_I_SB(dir)->dir_ra_bytes) {
> > > if (ra_pages) {
>>
>>> + unsigned long idx = DIV_ROUND_UP(ctx->pos, PAGE_SIZE);
>>> + pgoff_t ra_pages = DIV_ROUND_UP(
>>> + EROFS_I_SB(dir)->dir_ra_bytes, PAGE_SIZE);
>
> I put calculation here because if the value is zero, we don't need unnecessary calculation above, anyway, will update as you suggested, but let me know if you have any other concerns. :)
If only shift calculatiion is needed, I guess it
should not have much overhead, like:
if (ra_pages) {
pgoff_t idx = DIV_ROUND_UP_POW2(ctx->pos, PAGE_SIZE);
pgoff_t pages = min(nr_pages - idx, ra_pages);
...
Thanks,
Gao Xiang
^ permalink raw reply [flat|nested] 4+ messages in thread
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2025-07-14 9:39 [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir() Chao Yu
2025-07-17 8:26 ` Gao Xiang
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