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Thu, 17 Jul 2025 16:26:46 +0800 Message-ID: <631728e2-2808-47af-8db7-28cd8ae17622@linux.alibaba.com> Date: Thu, 17 Jul 2025 16:26:44 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] erofs: support to readahead dirent blocks in erofs_readdir() To: Chao Yu , xiang@kernel.org Cc: linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li References: <20250714093935.200749-1-chao@kernel.org> From: Gao Xiang In-Reply-To: <20250714093935.200749-1-chao@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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//dir_ra_bytes > - default value: 16384 > - disable readahead: set the value to 0 > > Signed-off-by: Chao Yu > --- > 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//dir_ra_bytes > +Date: July 2025 > +Contact: "Chao Yu" > +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/ */ > 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