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
Conflicts: include/linux/fs.h mm/readahead.c
Signed-off-by: ZhaoLong Wang wangzhaolong1@huawei.com --- 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 fb5accebdcdf..28b7634a6264 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -185,6 +185,12 @@ 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! @@ -1027,6 +1033,7 @@ struct file { struct address_space *f_mapping; errseq_t f_wb_err; errseq_t f_sb_err; /* for syncfs */ + fmode_t f_ctl_mode; } __randomize_layout __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */
diff --git a/mm/readahead.c b/mm/readahead.c index 6925e6959fd3..a1add9a4f77b 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -131,6 +131,7 @@
#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. @@ -668,10 +669,41 @@ 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, + i_size_read(file_inode(filp))); + unsigned long nrpages = round_up(size, 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 @@ -686,6 +718,12 @@ 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, + readahead_index(ractl), req_count, READAHEAD_FIRST_SIZE)) + return; + /* be dumb */ if (do_forced_ra) { force_page_cache_ra(ractl, req_count);