[RFC,3/4] PM: hibernate: Add support for LZ4 compression for hibernation
Commit Message
Extend the support for LZ4 compression to be used with hibernation.
The main idea is that different compression algorithms
have different characteristics and hibernation may benefit when it uses
any of these algorithms: a default algorithm, having higher
compression rate but is slower(compression/decompression) and a
secondary algorithm, that is faster(compression/decompression) but has
lower compression rate.
LZ4 algorithm has better decompression speeds over LZO. This reduces
the hibernation image restore time.
As per test results:
LZO LZ4
Size before Compression(bytes) 682696704 682393600
Size after Compression(bytes) 146502402 155993547
Decompression Rate 335.02 MB/s 501.05 MB/s
Restore time 4.4s 3.8s
LZO is the default compression algorithm used for hibernation. Enable
CONFIG_HIBERNATION_COMP_LZ4 to set the default compressor as LZ4.
Signed-off-by: Nikhil V <quic_nprakash@quicinc.com>
---
kernel/power/Kconfig | 5 +++++
kernel/power/hibernate.c | 25 ++++++++++++++++++++++---
kernel/power/power.h | 14 ++++++++++++++
3 files changed, 41 insertions(+), 3 deletions(-)
@@ -100,11 +100,16 @@ config HIBERNATION_COMP_LZO
bool "lzo"
depends on CRYPTO_LZO
+config HIBERNATION_COMP_LZ4
+ bool "lz4"
+ depends on CRYPTO_LZ4
+
endchoice
config HIBERNATION_DEF_COMP
string
default "lzo" if HIBERNATION_COMP_LZO
+ default "lz4" if HIBERNATION_COMP_LZ4
help
Default compressor to be used for hibernation.
@@ -721,6 +721,9 @@ static int load_image_and_restore(bool snapshot_test)
return error;
}
+#define COMPRESSION_ALGO_LZO "lzo"
+#define COMPRESSION_ALGO_LZ4 "lz4"
+
/**
* hibernate - Carry out system hibernation, including saving the image.
*/
@@ -780,11 +783,24 @@ int hibernate(void)
if (hibernation_mode == HIBERNATION_PLATFORM)
flags |= SF_PLATFORM_MODE;
- if (nocompress)
+ if (nocompress) {
flags |= SF_NOCOMPRESS_MODE;
- else
+ } else {
flags |= SF_CRC32_MODE;
+ /*
+ * By default, LZO compression is enabled. Use SF_COMPRESSION_ALG_LZ4
+ * to override this behaviour and use LZ4.
+ *
+ * Refer kernel/power/power.h for more details
+ */
+
+ if (!strcmp(hib_comp_algo, COMPRESSION_ALGO_LZ4))
+ flags |= SF_COMPRESSION_ALG_LZ4;
+ else
+ flags |= SF_COMPRESSION_ALG_LZO;
+ }
+
pm_pr_dbg("Writing hibernation image.\n");
error = swsusp_write(flags);
swsusp_free();
@@ -974,7 +990,10 @@ static int software_resume(void)
* the algorithm support.
*/
if (!(swsusp_header_flags & SF_NOCOMPRESS_MODE)) {
- strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
+ if (swsusp_header_flags & SF_COMPRESSION_ALG_LZ4)
+ strscpy(hib_comp_algo, COMPRESSION_ALGO_LZ4, sizeof(hib_comp_algo));
+ else
+ strscpy(hib_comp_algo, default_compressor, sizeof(hib_comp_algo));
if (crypto_has_comp(hib_comp_algo, 0, 0) != 1) {
pr_err("%s compression is not available\n", hib_comp_algo);
error = -EOPNOTSUPP;
@@ -167,11 +167,25 @@ extern int swsusp_swap_in_use(void);
* Flags that can be passed from the hibernatig hernel to the "boot" kernel in
* the image header.
*/
+#define SF_COMPRESSION_ALG_LZO 0 /* dummy, details given below */
#define SF_PLATFORM_MODE 1
#define SF_NOCOMPRESS_MODE 2
#define SF_CRC32_MODE 4
#define SF_HW_SIG 8
+/*
+ * Bit to indicate the compression algorithm to be used(for LZ4). The same
+ * could be checked while saving/loading image to/from disk to use the
+ * corresponding algorithms.
+ *
+ * By default, LZO compression is enabled if SF_CRC32_MODE is set. Use
+ * SF_COMPRESSION_ALG_LZ4 to override this behaviour and use LZ4.
+ *
+ * SF_CRC32_MODE, SF_COMPRESSION_ALG_LZO(dummy) -> Compression, LZO
+ * SF_CRC32_MODE, SF_COMPRESSION_ALG_LZ4 -> Compression, LZ4
+ */
+#define SF_COMPRESSION_ALG_LZ4 16
+
/* kernel/power/hibernate.c */
int swsusp_check(bool exclusive);
extern void swsusp_free(void);