From: Yufen Yu yuyufen@huawei.com
hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I7Y9JD CVE: NA
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In some scenario, likely spark-sql, almost all meta file's size is less then 2MB and applications read these smaller files in random mode. That means, it may issue multiple times random io to rotate disk, which can cause performance degradation.
To improve the small files random read, we try to read the first 2MB into pagecache on the first time of read. Then it can avoid multiple random io.
In fact, applications can call fadvise system with POSIX_FADV_WILLNEED to achieve this goal. But, some apps may cannot easily do that. So, we provide a new file flag FMODE_CTL_WILLNEED.
Signed-off-by: Yufen Yu yuyufen@huawei.com Reviewed-by: Hou Tao houtao1@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Conflicts: include/linux/fs.h Value '0x40000000' has been used for flag FMODE_BUF_RASYNC. Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Signed-off-by: ZhaoLong Wang wangzhaolong1@huawei.com
Conflicts: include/linux/fs.h mm/readahead.c --- include/linux/fs.h | 7 +++++++ mm/readahead.c | 40 +++++++++++++++++++++++++++++++++++++++- 2 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h index 133f0640fb24..931fe15dd17c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -189,6 +189,12 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, /* File supports async nowait buffered writes */ #define FMODE_BUF_WASYNC ((__force fmode_t)0x80000000)
+/* File mode control flag, expect random access pattern */ +#define FMODE_CTL_RANDOM ((__force fmode_t)0x1) + +/* File mode control flag, will try to read head of the file into pagecache */ +#define FMODE_CTL_WILLNEED ((__force fmode_t)0x2) + /* * Attribute flags. These should be or-ed together to figure out what * has been changed! @@ -974,6 +980,7 @@ struct file { atomic_long_t f_count; unsigned int f_flags; fmode_t f_mode; + fmode_t f_ctl_mode; struct mutex f_pos_lock; loff_t f_pos; struct fown_struct f_owner; diff --git a/mm/readahead.c b/mm/readahead.c index 47afbca1d122..7148f6f42ed4 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -132,6 +132,7 @@
#include "internal.h"
+#define READAHEAD_FIRST_SIZE (2 * 1024 * 1024) /* * Initialise a struct file's readahead state. Assumes that the caller has * memset *ra to zero. @@ -682,10 +683,41 @@ static void ondemand_readahead(struct readahead_control *ractl, page_cache_ra_order(ractl, ra, order); }
+/* + * Try to read first @ra_size from head of the file. + */ +static bool page_cache_readahead_from_head(struct address_space *mapping, + struct file *filp, pgoff_t offset, + unsigned long req_size, + unsigned long ra_size) +{ + struct backing_dev_info *bdi = inode_to_bdi(mapping->host); + struct file_ra_state *ra = &filp->f_ra; + unsigned long size = min_t(unsigned long, ra_size, + file_inode(filp)->i_size); + unsigned long nrpages = (size + PAGE_SIZE - 1) / PAGE_SIZE; + unsigned long max_pages; + unsigned int offs = 0; + + /* Cannot read date over target size, back to normal way */ + if (offset + req_size > nrpages) + return false; + + max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages); + max_pages = min(max_pages, nrpages); + while (offs < nrpages) { + force_page_cache_readahead(mapping, filp, offs, max_pages); + offs += max_pages; + } + return true; +} + void page_cache_sync_ra(struct readahead_control *ractl, unsigned long req_count) { - bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM); + bool do_forced_ra = ractl->file && + ((ractl->file->f_mode & FMODE_RANDOM) || + (ractl->file->f_ctl_mode & FMODE_CTL_RANDOM));
/* * Even if readahead is disabled, issue this request as readahead @@ -700,6 +732,12 @@ void page_cache_sync_ra(struct readahead_control *ractl, do_forced_ra = true; }
+ /* try to read first READAHEAD_FIRST_SIZE into pagecache */ + if (ractl->file && (ractl->file->f_ctl_mode & FMODE_CTL_WILLNEED) && + page_cache_readahead_from_head(ractl->mapping, ractl->file, + ractl->_index, req_count, READAHEAD_FIRST_SIZE)) + return; + /* be dumb */ if (do_forced_ra) { force_page_cache_ra(ractl, req_count);