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| author |   Huang Jianan <huangjianan@oppo.com> | 2021-03-29 09:23:06 +0800 |
|---|---|---|
| committer |   Gao Xiang <hsiangkao@redhat.com> | 2021-03-29 10:24:58 +0800 |
| commit | 5d50538fc567c6f3692dec1825fb38c5a0884d93 (patch) | |
| tree | 93389d04bec73677d08776d3306b8288949d192e /fs/erofs/decompressor.c | |
| parent | erofs: introduce erofs_sb_has_xxx() helpers (diff) | |
| download | linux-dev-5d50538fc567c6f3692dec1825fb38c5a0884d93.tar.xz linux-dev-5d50538fc567c6f3692dec1825fb38c5a0884d93.zip | |
erofs: support adjust lz4 history window size
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.
Link: https://lore.kernel.org/r/20210329012308.28743-3-hsiangkao@aol.com
Reviewed-by: Chao Yu <yuchao0@huawei.com>
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>
Diffstat (limited to 'fs/erofs/decompressor.c')
| -rw-r--r-- | fs/erofs/decompressor.c | 21 |
1 files changed, 17 insertions, 4 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) { |