From 9eec1d897139e5de287af5d559a02b811b844d82 Mon Sep 17 00:00:00 2001 From: Zheng Liang Date: Fri, 14 Jan 2022 14:03:31 -0800 Subject: squashfs: provide backing_dev_info in order to disable read-ahead Commit c1f6925e1091 ("mm: put readahead pages in cache earlier") causes the read performance of squashfs to deteriorate.Through testing, we find that the performance will be back by closing the readahead of squashfs. So we want to learn the way of ubifs, provides backing_dev_info and disable read-ahead We tested the following data by fio. squashfs image blocksize=128K test command: fio --name basic --bs=? --filename="/mnt/test_file" --rw=? --iodepth=1 --ioengine=psync --runtime=200 --time_based turn on squashfs readahead in 5.10 kernel bs(k) read/randread MB/s 4 randread 271 128 randread 231 1024 randread 246 4 read 310 128 read 245 1024 read 247 turn off squashfs readahead in 5.10 kernel bs(k) read/randread MB/s 4 randread 293 128 randread 330 1024 randread 363 4 read 338 128 read 360 1024 read 365 turn on squashfs readahead and revert the commit c1f6925e1091("mm: put readahead pages in cache earlier") in 5.10 kernel bs(k) read/randread MB/s 4 randread 289 128 randread 306 1024 randread 335 4 read 337 128 read 336 1024 read 338 Link: https://lkml.kernel.org/r/20211116113141.1391026-1-zhengliang6@huawei.com Signed-off-by: Zheng Liang Reviewed-by: Phillip Lougher Cc: Zhang Yi Cc: Hou Tao Cc: Miao Xie Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/squashfs/super.c | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'fs/squashfs') diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c index bb44ff4c5cc6..b1b556dbce12 100644 --- a/fs/squashfs/super.c +++ b/fs/squashfs/super.c @@ -29,6 +29,7 @@ #include #include #include +#include #include "squashfs_fs.h" #include "squashfs_fs_sb.h" @@ -112,6 +113,24 @@ static const struct squashfs_decompressor *supported_squashfs_filesystem( return decompressor; } +static int squashfs_bdi_init(struct super_block *sb) +{ + int err; + unsigned int major = MAJOR(sb->s_dev); + unsigned int minor = MINOR(sb->s_dev); + + bdi_put(sb->s_bdi); + sb->s_bdi = &noop_backing_dev_info; + + err = super_setup_bdi_name(sb, "squashfs_%u_%u", major, minor); + if (err) + return err; + + sb->s_bdi->ra_pages = 0; + sb->s_bdi->io_pages = 0; + + return 0; +} static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc) { @@ -127,6 +146,20 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc) TRACE("Entered squashfs_fill_superblock\n"); + /* + * squashfs provides 'backing_dev_info' in order to disable read-ahead. For + * squashfs, I/O is not deferred, it is done immediately in readpage, + * which means the user would always have to wait their own I/O. So the effect + * of readahead is very weak for squashfs. squashfs_bdi_init will set + * sb->s_bdi->ra_pages and sb->s_bdi->io_pages to 0 and close readahead for + * squashfs. + */ + err = squashfs_bdi_init(sb); + if (err) { + errorf(fc, "squashfs init bdi failed"); + return err; + } + sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL); if (sb->s_fs_info == NULL) { ERROR("Failed to allocate squashfs_sb_info\n"); -- cgit v1.2.3