| Message ID | 20190620160719.240682-7-gaoxiang25@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | staging: erofs: decompression inplace approach | expand |
On 2019/6/21 0:07, Gao Xiang wrote: > compressed data will be usually loaded into last pages of > the extent (the last page for 4k) for in-place decompression > (more specifically, in-place IO), as ilustration below, > > start of compressed logical extent > | end of this logical extent > | | > ______v___________________________v________ > ... | page 6 | page 7 | page 8 | page 9 | ... > |__________|__________|__________|__________| > . ^ . ^ > . |compressed| > . | data | > . . . > |< dstsize >|<margin>| > oend iend > op ip > > Therefore, it's possible to do decompression inplace (thus no > memcpy at all) if the margin is sufficient and safe enough [1], > and it can be implemented only for fixed-size output compression > compared with fixed-size input compression. > > No memcpy for most of in-place IO (about 99% of enwik9) after > decompression inplace is implemented and sequential read will > be improved of course (see the following patches for test results). > > [1] https://github.com/lz4/lz4/commit/b17f578a919b7e6b078cede2d52be29dd48c8e8c > https://github.com/lz4/lz4/commit/5997e139f53169fa3a1c1b4418d2452a90b01602 > > Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> Reviewed-by: Chao Yu <yuchao0@huawei.com>
diff --git a/drivers/staging/erofs/compress.h b/drivers/staging/erofs/compress.h index ebeccb1f4eae..c43aa3374d28 100644 --- a/drivers/staging/erofs/compress.h +++ b/drivers/staging/erofs/compress.h @@ -17,6 +17,7 @@ enum { }; struct z_erofs_decompress_req { + struct super_block *sb; struct page **in, **out; unsigned short pageofs_out; diff --git a/drivers/staging/erofs/decompressor.c b/drivers/staging/erofs/decompressor.c index c68d17b579e0..689fb8ec7032 100644 --- a/drivers/staging/erofs/decompressor.c +++ b/drivers/staging/erofs/decompressor.c @@ -14,6 +14,9 @@ #endif #define LZ4_MAX_DISTANCE_PAGES DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) +#ifndef LZ4_DECOMPRESS_INPLACE_MARGIN +#define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize) (((srcsize) >> 8) + 32) +#endif struct z_erofs_decompressor { /* @@ -132,9 +135,21 @@ static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out) copied = false; inlen = rq->inputsize - inputmargin; if (rq->inplace_io) { - src = generic_copy_inplace_data(rq, src, inputmargin); - inputmargin = 0; - copied = true; + const uint oend = (rq->pageofs_out + + rq->outputsize) & ~PAGE_MASK; + const uint nr = PAGE_ALIGN(rq->pageofs_out + + rq->outputsize) >> PAGE_SHIFT; + + if (rq->partial_decoding || + !(EROFS_SB(rq->sb)->requirements & + EROFS_REQUIREMENT_LZ4_0PADDING) || + rq->out[nr - 1] != rq->in[0] || + rq->inputsize - oend < + LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) { + src = generic_copy_inplace_data(rq, src, inputmargin); + inputmargin = 0; + copied = true; + } } ret = LZ4_decompress_safe_partial(src + inputmargin, out, diff --git a/drivers/staging/erofs/erofs_fs.h b/drivers/staging/erofs/erofs_fs.h index a05139f1df60..353322a3206c 100644 --- a/drivers/staging/erofs/erofs_fs.h +++ b/drivers/staging/erofs/erofs_fs.h @@ -21,7 +21,8 @@ * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be * incompatible with this kernel version. */ -#define EROFS_ALL_REQUIREMENTS 0 +#define EROFS_REQUIREMENT_LZ4_0PADDING 0x00000001 +#define EROFS_ALL_REQUIREMENTS EROFS_REQUIREMENT_LZ4_0PADDING struct erofs_super_block { /* 0 */__le32 magic; /* in the little endian */
compressed data will be usually loaded into last pages of the extent (the last page for 4k) for in-place decompression (more specifically, in-place IO), as ilustration below, start of compressed logical extent | end of this logical extent | | ______v___________________________v________ ... | page 6 | page 7 | page 8 | page 9 | ... |__________|__________|__________|__________| . ^ . ^ . |compressed| . | data | . . . |< dstsize >|<margin>| oend iend op ip Therefore, it's possible to do decompression inplace (thus no memcpy at all) if the margin is sufficient and safe enough [1], and it can be implemented only for fixed-size output compression compared with fixed-size input compression. No memcpy for most of in-place IO (about 99% of enwik9) after decompression inplace is implemented and sequential read will be improved of course (see the following patches for test results). [1] https://github.com/lz4/lz4/commit/b17f578a919b7e6b078cede2d52be29dd48c8e8c https://github.com/lz4/lz4/commit/5997e139f53169fa3a1c1b4418d2452a90b01602 Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> --- drivers/staging/erofs/compress.h | 1 + drivers/staging/erofs/decompressor.c | 21 ++++++++++++++++++--- drivers/staging/erofs/erofs_fs.h | 3 ++- 3 files changed, 21 insertions(+), 4 deletions(-)