From 062e4fee4400f283307cf8ac1b7931c939010229 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Sun, 26 Oct 2008 16:58:25 +0200 Subject: UBIFS: slight compression optimization 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 --- fs/ubifs/compress.c | 6 +++--- fs/ubifs/ubifs-media.h | 7 +++++++ 2 files changed, 10 insertions(+), 3 deletions(-) (limited to 'fs/ubifs') diff --git a/fs/ubifs/compress.c b/fs/ubifs/compress.c index a0ada596b17c..6414d50780e1 100644 --- a/fs/ubifs/compress.c +++ b/fs/ubifs/compress.c @@ -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, - * rather than any defined minimum compression ratio or amount. + * If the data compressed only slightly, it is better to leave it + * 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; return; diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h index 0b378042a3a2..b25fc36cf72f 100644 --- a/fs/ubifs/ubifs-media.h +++ b/fs/ubifs/ubifs-media.h @@ -51,6 +51,13 @@ */ #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 */ #define UBIFS_ROOT_INO 1 -- cgit v1.2.3