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UBIFS: slight compression optimization

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If data does not compress, it is better to leave it uncompressed
because we'll read it faster then. So do not compress data if we
save less than 64 bytes.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commit is contained in:
Artem Bityutskiy 2008-10-26 16:58:25 +02:00
parent f6f7b52e2f
commit 062e4fee44
2 changed files with 10 additions and 3 deletions
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6
fs/ubifs/compress.c
View File

@ -119,10 +119,10 @@ void ubifs_compress(const void *in_buf, int in_len, void *out_buf, int *out_len,
} }
/* /*
* Presently, we just require that compression results in less data, * If the data compressed only slightly, it is better to leave it
* rather than any defined minimum compression ratio or amount. * uncompressed to improve read speed.
*/ */
if (ALIGN(*out_len, 8) >= ALIGN(in_len, 8)) if (in_len - *out_len < UBIFS_MIN_COMPRESS_DIFF)
goto no_compr; goto no_compr;
return; return;

7
fs/ubifs/ubifs-media.h
View File

@ -51,6 +51,13 @@
*/ */
#define UBIFS_MIN_COMPR_LEN 128 #define UBIFS_MIN_COMPR_LEN 128
/*
* If compressed data length is less than %UBIFS_MIN_COMPRESS_DIFF bytes
* shorter than uncompressed data length, UBIFS preferes to leave this data
* node uncompress, because it'll be read faster.
*/
#define UBIFS_MIN_COMPRESS_DIFF 64
/* Root inode number */ /* Root inode number */
#define UBIFS_ROOT_INO 1 #define UBIFS_ROOT_INO 1