Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=3b23c1f5fa7e4c99e9451958a1004ef7434a71f0
Commit: 3b23c1f5fa7e4c99e9451958a1004ef7434a71f0
Parent: c799aca31bfe61ba3a91133acf5a13a0773087d4
Author: Richard Purdie <[EMAIL PROTECTED]>
AuthorDate: Tue Jul 10 10:28:42 2007 +0100
Committer: David Woodhouse <[EMAIL PROTECTED]>
CommitDate: Wed Jul 11 15:04:38 2007 +0100
[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 <[EMAIL PROTECTED]>
Signed-off-by: David Woodhouse <[EMAIL PROTECTED]>
---
fs/Kconfig | 7 +++++++
fs/jffs2/compr.c | 45 ++++++++++++++++++++++++++++++++++++++++-----
fs/jffs2/compr.h | 3 +++
3 files changed, 50 insertions(+), 5 deletions(-)
diff --git a/fs/Kconfig b/fs/Kconfig
index a2ec0b3..42cfb7d 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 bcc28d2..86739ee 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 a54828a..e1b7efb 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;
-
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