From: huangjianan <[email protected]> lz4 uses LZ4_DISTANCE_MAX to record history preservation. When using rolling decompression, a block with a higher compression ratio will cause a larger memory allocation (up to 64k). It may cause a large resource burden in extreme cases on devices with small memory and a large number of concurrent IOs. So appropriately reducing this value can improve performance.
Decreasing this value will reduce the compression ratio (except when input_size <LZ4_DISTANCE_MAX). But considering that erofs currently only supports 4k output, reducing this value will not significantly reduce the compression benefits. Signed-off-by: Huang Jianan <[email protected]> Signed-off-by: Guo Weichao <[email protected]> --- changes since previous version - change compr_alg to lz4_max_distance - calculate lz4_max_distance_pages when reading super_block fs/erofs/decompressor.c | 12 ++++++++---- fs/erofs/erofs_fs.h | 3 ++- fs/erofs/internal.h | 3 +++ fs/erofs/super.c | 5 +++++ 4 files changed, 18 insertions(+), 5 deletions(-) diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c index 1cb1ffd10569..fb2b4f1b8806 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -36,22 +36,26 @@ static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq, struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL }; unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES, BITS_PER_LONG)] = { 0 }; + unsigned int lz4_max_distance_pages = LZ4_MAX_DISTANCE_PAGES; void *kaddr = NULL; unsigned int i, j, top; + if (EROFS_SB(rq->sb)->lz4_max_distance_pages) + lz4_max_distance_pages = EROFS_SB(rq->sb)->lz4_max_distance_pages; + top = 0; for (i = j = 0; i < nr; ++i, ++j) { struct page *const page = rq->out[i]; struct page *victim; - if (j >= LZ4_MAX_DISTANCE_PAGES) + if (j >= lz4_max_distance_pages) j = 0; /* 'valid' bounced can only be tested after a complete round */ if (test_bit(j, bounced)) { - DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES); - DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES); - availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES]; + DBG_BUGON(i < lz4_max_distance_pages); + DBG_BUGON(top >= lz4_max_distance_pages); + availables[top++] = rq->out[i - lz4_max_distance_pages]; } if (page) { diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h index 9ad1615f4474..5eb37002b1a3 100644 --- a/fs/erofs/erofs_fs.h +++ b/fs/erofs/erofs_fs.h @@ -39,7 +39,8 @@ struct erofs_super_block { __u8 uuid[16]; /* 128-bit uuid for volume */ __u8 volume_name[16]; /* volume name */ __le32 feature_incompat; - __u8 reserved2[44]; + __le16 lz4_max_distance; /* lz4 max distance */ + __u8 reserved2[42]; }; /* diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h index 67a7ec945686..7457710a763a 100644 --- a/fs/erofs/internal.h +++ b/fs/erofs/internal.h @@ -70,6 +70,9 @@ struct erofs_sb_info { /* pseudo inode to manage cached pages */ struct inode *managed_cache; + + /* lz4 max distance pages */ + u16 lz4_max_distance_pages; #endif /* CONFIG_EROFS_FS_ZIP */ u32 blocks; u32 meta_blkaddr; diff --git a/fs/erofs/super.c b/fs/erofs/super.c index d5a6b9b888a5..3a3d235de7cc 100644 --- a/fs/erofs/super.c +++ b/fs/erofs/super.c @@ -174,6 +174,11 @@ static int erofs_read_superblock(struct super_block *sb) sbi->islotbits = ilog2(sizeof(struct erofs_inode_compact)); sbi->root_nid = le16_to_cpu(dsb->root_nid); sbi->inos = le64_to_cpu(dsb->inos); +#ifdef CONFIG_EROFS_FS_ZIP + if (dsb->lz4_max_distance) + sbi->lz4_max_distance_pages = + DIV_ROUND_UP(le16_to_cpu(dsb->lz4_max_distance), PAGE_SIZE) + 1; +#endif sbi->build_time = le64_to_cpu(dsb->build_time); sbi->build_time_nsec = le32_to_cpu(dsb->build_time_nsec); -- 2.25.1
