[PATCHv9 1/7] zram: introduce compressing backend abstraction
ZRAM performs direct LZO compression algorithm calls, making it the one and
only option. While LZO is generally performs well, LZ4 algorithm tends to
have a faster decompression (see http://code.google.com/p/lz4/ for full
report)
NameRatio C.speed D.speed
MB/sMB/s
LZ4 (r101) 2.0844221820
LZO 2.062.106414 600
Thus, users who have mostly read (decompress) usage scenarious or mixed
workflow (writes with relatively high read ops number) will benefit from
using LZ4 compression backend.
Introduce compressing backend abstraction zcomp in order to support multiple
compression algorithms with the following set of operations:
.create
.destroy
.compress
.decompress
Schematically zram write() usually contains the following steps:
0) preparation (decompression of partioal IO, etc.)
1) lock buffer_lock mutex (protects meta compress buffers)
2) compress (using meta compress buffers)
3) alloc and map zs_pool object
4) copy compressed data (from meta compress buffers) to object allocated by 3)
5) free previous pool page, assign a new one
6) unlock buffer_lock mutex
As we can see, compressing buffers must remain untouched from 1) to 4),
because, otherwise, concurrent write() can overwrite data. At the same time,
zram_meta must be aware of a) specific compression algorithm memory requirements
and b) necessary locking to protect compression buffers. To remove requirement
a) new struct zcomp_strm introduced, which contains a compress/decompress
`buffer' and compression algorithm `private' part. While struct zcomp implements
zcomp_strm stream handling and locking and removes requirement b) from zram
meta.
zcomp ->create() and ->destroy(), respectively, allocate and deallocate
algorithm
specific zcomp_strm `private' part.
Every zcomp has zcomp stream and mutex to protect its compression stream. Stream
usage semantics remains the same -- only one write can hold stream lock and use
its buffers. zcomp_strm_find() turns caller into exclusive user of a stream
(holding stream mutex until zram release stream), and zcomp_strm_release()
makes zcomp stream available (unlock the stream mutex). Hence no concurrent
write (compression) operations possible at the moment.
iozone -t 3 -R -r 16K -s 60M -I +Z
testbase patched
--
Initial write 597992.91 591660.58
Rewrite 609674.34 616054.97
Read 2404771.75 2452909.12
Re-read 2459216.81 2470074.44
Reverse Read 1652769.66 1589128.66
Stride read 2202441.81 2202173.31
Random read 2236311.47 2276565.31
Mixed workload 1423760.41 1709760.06
Random write 579584.08 615933.86
Pwrite 597550.02 594933.70
Pread 1703672.53 1718126.72
Fwrite 1330497.06 1461054.00
Fread 3922851.00 3957242.62
Usage examples:
comp = zcomp_create(NAME) /* NAME e.g. "lzo" */
which initialises compressing backend if requested algorithm is supported.
Compress:
zstrm = zcomp_strm_find(comp)
zcomp_compress(comp, zstrm, src, _len)
[..] /* copy compressed data */
zcomp_strm_release(comp, zstrm)
Decompress:
zcomp_decompress(comp, src, src_len, dst);
Free compessing backend and its zcomp stream:
zcomp_destroy(comp)
Signed-off-by: Sergey Senozhatsky
---
drivers/block/zram/zcomp.c | 115 +
drivers/block/zram/zcomp.h | 58 +
drivers/block/zram/zcomp_lzo.c | 47 +
drivers/block/zram/zcomp_lzo.h | 17 ++
4 files changed, 237 insertions(+)
create mode 100644 drivers/block/zram/zcomp.c
create mode 100644 drivers/block/zram/zcomp.h
create mode 100644 drivers/block/zram/zcomp_lzo.c
create mode 100644 drivers/block/zram/zcomp_lzo.h
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
new file mode 100644
index 000..22f4ae2
--- /dev/null
+++ b/drivers/block/zram/zcomp.c
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2014 Sergey Senozhatsky.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include
+#include
+#include
+#include
+#include
+
+#include "zcomp.h"
+#include "zcomp_lzo.h"
+
+static struct zcomp_backend *find_backend(const char *compress)
+{
+ if (strncmp(compress, "lzo", 3) == 0)
+ return _lzo;
+ return NULL;
+}
+
+static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
+{
+ if (zstrm->private)
+ comp->backend->destroy(zstrm->private);
+ free_pages((unsigned
[PATCHv9 1/7] zram: introduce compressing backend abstraction
ZRAM performs direct LZO compression algorithm calls, making it the one and
only option. While LZO is generally performs well, LZ4 algorithm tends to
have a faster decompression (see http://code.google.com/p/lz4/ for full
report)
NameRatio C.speed D.speed
MB/sMB/s
LZ4 (r101) 2.0844221820
LZO 2.062.106414 600
Thus, users who have mostly read (decompress) usage scenarious or mixed
workflow (writes with relatively high read ops number) will benefit from
using LZ4 compression backend.
Introduce compressing backend abstraction zcomp in order to support multiple
compression algorithms with the following set of operations:
.create
.destroy
.compress
.decompress
Schematically zram write() usually contains the following steps:
0) preparation (decompression of partioal IO, etc.)
1) lock buffer_lock mutex (protects meta compress buffers)
2) compress (using meta compress buffers)
3) alloc and map zs_pool object
4) copy compressed data (from meta compress buffers) to object allocated by 3)
5) free previous pool page, assign a new one
6) unlock buffer_lock mutex
As we can see, compressing buffers must remain untouched from 1) to 4),
because, otherwise, concurrent write() can overwrite data. At the same time,
zram_meta must be aware of a) specific compression algorithm memory requirements
and b) necessary locking to protect compression buffers. To remove requirement
a) new struct zcomp_strm introduced, which contains a compress/decompress
`buffer' and compression algorithm `private' part. While struct zcomp implements
zcomp_strm stream handling and locking and removes requirement b) from zram
meta.
zcomp -create() and -destroy(), respectively, allocate and deallocate
algorithm
specific zcomp_strm `private' part.
Every zcomp has zcomp stream and mutex to protect its compression stream. Stream
usage semantics remains the same -- only one write can hold stream lock and use
its buffers. zcomp_strm_find() turns caller into exclusive user of a stream
(holding stream mutex until zram release stream), and zcomp_strm_release()
makes zcomp stream available (unlock the stream mutex). Hence no concurrent
write (compression) operations possible at the moment.
iozone -t 3 -R -r 16K -s 60M -I +Z
testbase patched
--
Initial write 597992.91 591660.58
Rewrite 609674.34 616054.97
Read 2404771.75 2452909.12
Re-read 2459216.81 2470074.44
Reverse Read 1652769.66 1589128.66
Stride read 2202441.81 2202173.31
Random read 2236311.47 2276565.31
Mixed workload 1423760.41 1709760.06
Random write 579584.08 615933.86
Pwrite 597550.02 594933.70
Pread 1703672.53 1718126.72
Fwrite 1330497.06 1461054.00
Fread 3922851.00 3957242.62
Usage examples:
comp = zcomp_create(NAME) /* NAME e.g. lzo */
which initialises compressing backend if requested algorithm is supported.
Compress:
zstrm = zcomp_strm_find(comp)
zcomp_compress(comp, zstrm, src, dst_len)
[..] /* copy compressed data */
zcomp_strm_release(comp, zstrm)
Decompress:
zcomp_decompress(comp, src, src_len, dst);
Free compessing backend and its zcomp stream:
zcomp_destroy(comp)
Signed-off-by: Sergey Senozhatsky sergey.senozhat...@gmail.com
---
drivers/block/zram/zcomp.c | 115 +
drivers/block/zram/zcomp.h | 58 +
drivers/block/zram/zcomp_lzo.c | 47 +
drivers/block/zram/zcomp_lzo.h | 17 ++
4 files changed, 237 insertions(+)
create mode 100644 drivers/block/zram/zcomp.c
create mode 100644 drivers/block/zram/zcomp.h
create mode 100644 drivers/block/zram/zcomp_lzo.c
create mode 100644 drivers/block/zram/zcomp_lzo.h
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
new file mode 100644
index 000..22f4ae2
--- /dev/null
+++ b/drivers/block/zram/zcomp.c
@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2014 Sergey Senozhatsky.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include linux/kernel.h
+#include linux/string.h
+#include linux/slab.h
+#include linux/wait.h
+#include linux/sched.h
+
+#include zcomp.h
+#include zcomp_lzo.h
+
+static struct zcomp_backend *find_backend(const char *compress)
+{
+ if (strncmp(compress, lzo, 3) == 0)
+ return zcomp_lzo;
+ return NULL;
+}
+
+static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
+{
+ if (zstrm-private)
