Hi Daeho,
On 2020/5/8 9:28, Daeho Jeong wrote:
> Hi Chao,
>
> IIUC, you are trying not to use ZSTD_compressBound() to save the memory
> space. Am I right?
>
> Then, how about LZ4_compressBound() for LZ4 and lzo1x_worst_compress() for
> LZO?
Oops, it looks those limits were wrongly used...
#define LZ4_COMPRESSBOUND(isize) (\
(unsigned int)(isize) > (unsigned int)LZ4_MAX_INPUT_SIZE \
? 0 \
: (isize) + ((isize)/255) + 16)
#define lzo1x_worst_compress(x) ((x) + ((x) / 16) + 64 + 3 + 2)
Newly calculated boundary size is larger than target buffer size.
However comments on LZ4_compress_default() said:
...
* @maxOutputSize: full or partial size of buffer 'dest'
* which must be already allocated
...
int LZ4_compress_default(const char *source, char *dest, int inputSize,
int maxOutputSize, void *wrkmem);
And @out_len in lzo1x_1_compress() was passed as an output parameter to
pass length of data that compressor compressed into @out buffer.
Let me know if I missed sth.
Thannks,
> Could we save more memory space for these two cases like ZSTD?
> As you know, we are using 5 pages compression buffer for LZ4 and LZO in
> compress_log_size=2,
> and if the compressed data doesn't fit in 3 pages, it returns -EAGAIN to
> give up compressing that one.
>
> Thanks,
>
> 2020년 5월 8일 (금) 오전 10:17, Chao Yu <yuch...@huawei.com>님이 작성:
>
>> During zstd compression, ZSTD_endStream() may return non-zero value
>> because distination buffer is full, but there is still compressed data
>> remained in intermediate buffer, it means that zstd algorithm can not
>> save at last one block space, let's just writeback raw data instead of
>> compressed one, this can fix data corruption when decompressing
>> incomplete stored compression data.
>>
>> Signed-off-by: Daeho Jeong <daehoje...@google.com>
>> Signed-off-by: Chao Yu <yuch...@huawei.com>
>> ---
>> fs/f2fs/compress.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>> index c22cc0d37369..5e4947250262 100644
>> --- a/fs/f2fs/compress.c
>> +++ b/fs/f2fs/compress.c
>> @@ -358,6 +358,13 @@ static int zstd_compress_pages(struct compress_ctx
>> *cc)
>> return -EIO;
>> }
>>
>> + /*
>> + * there is compressed data remained in intermediate buffer due to
>> + * no more space in cbuf.cdata
>> + */
>> + if (ret)
>> + return -EAGAIN;
>> +
>> cc->clen = outbuf.pos;
>> return 0;
>> }
>> --
>> 2.18.0.rc1
>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> linux-f2fs-de...@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>>
>
