Messages in this thread | | | Subject | Re: [PATCH 2/4] erofs: support adjust lz4 history window size | From | Chao Yu <> | Date | Sat, 27 Mar 2021 17:34:33 +0800 |
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On 2021/3/27 11:49, Gao Xiang wrote: > From: Huang Jianan <huangjianan@oppo.com> > > 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. > > The maximum value of LZ4_DISTANCE_MAX defined by lz4 is 64k, and > we can only reduce this value. For the old kernel, it just can't > reduce the memory allocation during rolling decompression without > affecting the decompression result. > > Signed-off-by: Huang Jianan <huangjianan@oppo.com> > Signed-off-by: Guo Weichao <guoweichao@oppo.com> > [ Gao Xiang: introduce struct erofs_sb_lz4_info for configurations. ] > Signed-off-by: Gao Xiang <hsiangkao@redhat.com> > --- > fs/erofs/decompressor.c | 21 +++++++++++++++++---- > fs/erofs/erofs_fs.h | 3 ++- > fs/erofs/internal.h | 19 +++++++++++++++++++ > fs/erofs/super.c | 4 +++- > 4 files changed, 41 insertions(+), 6 deletions(-) > > diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c > index 80e8871aef71..93411e9df9b6 100644 > --- a/fs/erofs/decompressor.c > +++ b/fs/erofs/decompressor.c > @@ -28,6 +28,17 @@ struct z_erofs_decompressor { > char *name; > }; > > +int z_erofs_load_lz4_config(struct super_block *sb, > + struct erofs_super_block *dsb) > +{ > + u16 distance = le16_to_cpu(dsb->lz4_max_distance); > + > + EROFS_SB(sb)->lz4.max_distance_pages = distance ? > + DIV_ROUND_UP(distance, PAGE_SIZE) + 1 : > + LZ4_MAX_DISTANCE_PAGES; > + return 0; > +} > + > static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq, > struct list_head *pagepool) > { > @@ -36,6 +47,8 @@ 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 = > + EROFS_SB(rq->sb)->lz4.max_distance_pages; > void *kaddr = NULL; > unsigned int i, j, top; > > @@ -44,14 +57,14 @@ static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq, > 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..b27d0e4e4ab5 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;
It missed to add comments, otherwise it looks good to me.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Thanks,
> + __u8 reserved2[42]; > }; > > /* > diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h > index d29fc0c56032..1de60992c3dd 100644 > --- a/fs/erofs/internal.h > +++ b/fs/erofs/internal.h > @@ -59,6 +59,12 @@ struct erofs_fs_context { > unsigned int mount_opt; > }; > > +/* all filesystem-wide lz4 configurations */ > +struct erofs_sb_lz4_info { > + /* # of pages needed for EROFS lz4 rolling decompression */ > + u16 max_distance_pages; > +}; > + > struct erofs_sb_info { > #ifdef CONFIG_EROFS_FS_ZIP > /* list for all registered superblocks, mainly for shrinker */ > @@ -72,6 +78,8 @@ struct erofs_sb_info { > > /* pseudo inode to manage cached pages */ > struct inode *managed_cache; > + > + struct erofs_sb_lz4_info lz4; > #endif /* CONFIG_EROFS_FS_ZIP */ > u32 blocks; > u32 meta_blkaddr; > @@ -432,6 +440,8 @@ int erofs_try_to_free_all_cached_pages(struct erofs_sb_info *sbi, > struct erofs_workgroup *egrp); > int erofs_try_to_free_cached_page(struct address_space *mapping, > struct page *page); > +int z_erofs_load_lz4_config(struct super_block *sb, > + struct erofs_super_block *dsb); > #else > static inline void erofs_shrinker_register(struct super_block *sb) {} > static inline void erofs_shrinker_unregister(struct super_block *sb) {} > @@ -439,6 +449,15 @@ static inline int erofs_init_shrinker(void) { return 0; } > static inline void erofs_exit_shrinker(void) {} > static inline int z_erofs_init_zip_subsystem(void) { return 0; } > static inline void z_erofs_exit_zip_subsystem(void) {} > +static inline int z_erofs_load_lz4_config(struct super_block *sb, > + struct erofs_super_block *dsb) > +{ > + if (dsb->lz4_max_distance) { > + erofs_err(sb, "lz4 algorithm isn't enabled"); > + return -EINVAL; > + } > + return 0; > +} > #endif /* !CONFIG_EROFS_FS_ZIP */ > > #define EFSCORRUPTED EUCLEAN /* Filesystem is corrupted */ > diff --git a/fs/erofs/super.c b/fs/erofs/super.c > index 991b99eaf22a..3212e4f73f85 100644 > --- a/fs/erofs/super.c > +++ b/fs/erofs/super.c > @@ -187,7 +187,9 @@ static int erofs_read_superblock(struct super_block *sb) > ret = -EFSCORRUPTED; > goto out; > } > - ret = 0; > + > + /* parse on-disk compression configurations */ > + ret = z_erofs_load_lz4_config(sb, dsb); > out: > kunmap(page); > put_page(page); >
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