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authorRichard Purdie <rpurdie@openedhand.com>2007-07-10 10:28:42 +0100
committerDavid Woodhouse <dwmw2@infradead.org>2007-07-11 15:04:38 +0100
commit3b23c1f5fa7e4c99e9451958a1004ef7434a71f0 (patch)
tree2442c774918a422dee47b44d92515fcfb1897f35
parentc799aca31bfe61ba3a91133acf5a13a0773087d4 (diff)
[JFFS2] Add a "favourlzo" compression mode
Add a "favourlzo" compression mode to jffs2 which tries to optimise by size but gives lzo an advantage when comparing sizes. This means the faster lzo algorithm can be preferred when there isn't much difference in compressed size (the exact threshold can be changed). Signed-off-by: Richard Purdie <rpurdie@openedhand.com> Signed-off-by: David Woodhouse <dwmw2@infradead.org>
-rw-r--r--fs/Kconfig7
-rw-r--r--fs/jffs2/compr.c45
-rw-r--r--fs/jffs2/compr.h3
3 files changed, 50 insertions, 5 deletions
diff --git a/fs/Kconfig b/fs/Kconfig
index a2ec0b375df..42cfb7dc95b 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -1364,6 +1364,13 @@ config JFFS2_CMODE_SIZE
Tries all compressors and chooses the one which has the smallest
result.
+config JFFS2_CMODE_FAVOURLZO
+ bool "Favour LZO"
+ help
+ Tries all compressors and chooses the one which has the smallest
+ result but gives some preference to LZO (which has faster
+ decompression) at the expense of size.
+
endchoice
config CRAMFS
diff --git a/fs/jffs2/compr.c b/fs/jffs2/compr.c
index bcc28d266a1..86739ee53b3 100644
--- a/fs/jffs2/compr.c
+++ b/fs/jffs2/compr.c
@@ -24,6 +24,34 @@ static int jffs2_compression_mode = JFFS2_COMPR_MODE_PRIORITY;
/* Statistics for blocks stored without compression */
static uint32_t none_stat_compr_blocks=0,none_stat_decompr_blocks=0,none_stat_compr_size=0;
+
+/*
+ * Return 1 to use this compression
+ */
+static int jffs2_is_best_compression(struct jffs2_compressor *this,
+ struct jffs2_compressor *best, uint32_t size, uint32_t bestsize)
+{
+ switch (jffs2_compression_mode) {
+ case JFFS2_COMPR_MODE_SIZE:
+ if (bestsize > size)
+ return 1;
+ return 0;
+ case JFFS2_COMPR_MODE_FAVOURLZO:
+ if ((this->compr == JFFS2_COMPR_LZO) && (bestsize > size))
+ return 1;
+ if ((best->compr != JFFS2_COMPR_LZO) && (bestsize > size))
+ return 1;
+ if ((this->compr == JFFS2_COMPR_LZO) && (bestsize > (size * FAVOUR_LZO_PERCENT / 100)))
+ return 1;
+ if ((bestsize * FAVOUR_LZO_PERCENT / 100) > size)
+ return 1;
+
+ return 0;
+ }
+ /* Shouldn't happen */
+ return 0;
+}
+
/* jffs2_compress:
* @data: Pointer to uncompressed data
* @cdata: Pointer to returned pointer to buffer for compressed data
@@ -90,6 +118,7 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
kfree(output_buf);
break;
case JFFS2_COMPR_MODE_SIZE:
+ case JFFS2_COMPR_MODE_FAVOURLZO:
orig_slen = *datalen;
orig_dlen = *cdatalen;
spin_lock(&jffs2_compressor_list_lock);
@@ -98,7 +127,7 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
if ((!this->compress)||(this->disabled))
continue;
/* Allocating memory for output buffer if necessary */
- if ((this->compr_buf_size<orig_dlen)&&(this->compr_buf)) {
+ if ((this->compr_buf_size < orig_slen) && (this->compr_buf)) {
spin_unlock(&jffs2_compressor_list_lock);
kfree(this->compr_buf);
spin_lock(&jffs2_compressor_list_lock);
@@ -107,15 +136,15 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
}
if (!this->compr_buf) {
spin_unlock(&jffs2_compressor_list_lock);
- tmp_buf = kmalloc(orig_dlen,GFP_KERNEL);
+ tmp_buf = kmalloc(orig_slen, GFP_KERNEL);
spin_lock(&jffs2_compressor_list_lock);
if (!tmp_buf) {
- printk(KERN_WARNING "JFFS2: No memory for compressor allocation. (%d bytes)\n",orig_dlen);
+ printk(KERN_WARNING "JFFS2: No memory for compressor allocation. (%d bytes)\n", orig_slen);
continue;
}
else {
this->compr_buf = tmp_buf;
- this->compr_buf_size = orig_dlen;
+ this->compr_buf_size = orig_slen;
}
}
this->usecount++;
@@ -126,7 +155,8 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
spin_lock(&jffs2_compressor_list_lock);
this->usecount--;
if (!compr_ret) {
- if ((!best_dlen)||(best_dlen>*cdatalen)) {
+ if (((!best_dlen) || jffs2_is_best_compression(this, best, *cdatalen, best_dlen))
+ && (*cdatalen < *datalen)) {
best_dlen = *cdatalen;
best_slen = *datalen;
best = this;
@@ -298,9 +328,14 @@ int __init jffs2_compressors_init(void)
jffs2_compression_mode = JFFS2_COMPR_MODE_SIZE;
D1(printk(KERN_INFO "JFFS2: default compression mode: size\n");)
#else
+#ifdef CONFIG_JFFS2_CMODE_FAVOURLZO
+ jffs2_compression_mode = JFFS2_COMPR_MODE_FAVOURLZO;
+ D1(printk(KERN_INFO "JFFS2: default compression mode: favourlzo\n");)
+#else
D1(printk(KERN_INFO "JFFS2: default compression mode: priority\n");)
#endif
#endif
+#endif
return 0;
}
diff --git a/fs/jffs2/compr.h b/fs/jffs2/compr.h
index a54828a4e9c..e1b7efb70aa 100644
--- a/fs/jffs2/compr.h
+++ b/fs/jffs2/compr.h
@@ -38,6 +38,9 @@
#define JFFS2_COMPR_MODE_NONE 0
#define JFFS2_COMPR_MODE_PRIORITY 1
#define JFFS2_COMPR_MODE_SIZE 2
+#define JFFS2_COMPR_MODE_FAVOURLZO 3
+
+#define FAVOUR_LZO_PERCENT 80
struct jffs2_compressor {
struct list_head list;