Hi Chao, On Sat, Mar 27, 2021 at 05:34:33PM +0800, Chao Yu wrote: > On 2021/3/27 11:49, Gao Xiang wrote: > > From: Huang Jianan <huangjia...@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 <huangjia...@oppo.com> > > Signed-off-by: Guo Weichao <guoweic...@oppo.com> > > [ Gao Xiang: introduce struct erofs_sb_lz4_info for configurations. ] > > Signed-off-by: Gao Xiang <hsiang...@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. >
Yes, it needs some inline comment description, will update in the next version. > Reviewed-by: Chao Yu <yuch...@huawei.com> > Thanks for the review! Thanks, Gao Xiang > Thanks, >