[PATCH v5 0/3]: lib/lzo: run-length encoding support

[PATCH v5 0/3]: lib/lzo: run-length encoding support

[Dave Rodgman]

Hi,

Following on from the previous lzo-rle patchset:

https://lkml.org/lkml/2018/11/30/972

This patchset contains only the RLE patches, and should be applied on top of
the non-RLE patches ( https://lkml.org/lkml/2019/2/5/366 ).


Previously, some questions were raised around the RLE patches. I've done some
additional benchmarking to answer these questions. In short:

 - RLE offers significant additional performance (data-dependent)
 - I didn't measure any regressions that were clearly outside the noise


One concern with this patchset was around performance - specifically, measuring
RLE impact separately from Matt Sealey's patches (CTZ & fast copy). I have done
some additional benchmarking which I hope clarifies the benefits of each part
of the patchset.

Firstly, I've captured some memory via /dev/fmem from a Chromebook with many
tabs open which is starting to swap, and then split this into 4178 4k pages.
I've excluded the all-zero pages (as zram does), and also the no-zero pages
(which won't tell us anything about RLE performance). This should give a
realistic test dataset for zram. What I found was that the data is VERY
bimodal: 44% of pages in this dataset contain 5% or fewer zeros, and 44%
contain over 90% zeros (30% if you include the no-zero pages). This supports
the idea of special-casing zeros in zram.

Next, I've benchmarked four variants of lzo on these pages (on 64-bit Arm at
max frequency): baseline LZO; baseline + Matt Sealey's patches (aka MS);
baseline + RLE only; baseline + MS + RLE. Numbers are for weighted roundtrip
throughput (the weighting reflects that zram does more compression than
decompression).

https://drive.google.com/file/d/1VLtLjRVxgUNuWFOxaGPwJYhl_hMQXpHe/view?usp=sharing

Matt's patches help in all cases for Arm (and no effect on Intel), as expected.

RLE also behaves as expected: with few zeros present, it makes no difference;
above ~75%, it gives a good improvement (50 - 300 MB/s on top of the benefit
from Matt's patches).

Best performance is seen with both MS and RLE patches.

Finally, I have benchmarked the same dataset on an x86-64 device. Here, the
MS patches make no difference (as expected); RLE helps, similarly as on Arm.
There were no definite regressions; allowing for observational error, 0.1%
(3/4178) of cases had a regression > 1 standard deviation, of which the largest
was 4.6% (1.2 standard deviations). I think this is probably within the noise.

https://drive.google.com/file/d/1xCUVwmiGD0heEMx5gcVEmLBI4eLaageV/view?usp=sharing

One point to note is that the graphs show RLE appears to help very slightly
with no zeros present! This is because the extra code causes the clang
optimiser to change code layout in a way that happens to have a significant
benefit. Taking baseline LZO and adding a do-nothing line like
"__builtin_prefetch(out_len);" immediately before the "goto next" has the same
effect. So this is a real, but basically spurious effect - it's small enough
not to upset the overall findings.

Dave

[PATCH v5 1/3] lib/lzo: implement run-length encoding

[Dave Rodgman]

When using zram, we frequently encounter long runs of zero bytes.
This adds a special case which identifies runs of zeros and encodes
them using run-length encoding.

This is faster for both compression and decompresion. For
high-entropy data which doesn't hit this case, impact is minimal.

Compression ratio is within a few percent in all cases.

This modifies the bitstream in a way which is backwards compatible
(i.e., we can decompress old bitstreams, but old versions of lzo
cannot decompress new bitstreams).

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Markus F.X.J. Oberhumer <markus@oberhumer.com>
Cc: Matt Sealey <matt.sealey@arm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <nitingupta910@gmail.com>
Cc: Richard Purdie <rpurdie@openedhand.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sonny Rao <sonnyrao@google.com>
---
 Documentation/lzo.txt           |  35 ++++++++---
 include/linux/lzo.h             |   2 +-
 lib/lzo/lzo1x_compress.c        | 100 ++++++++++++++++++++++++++++----
 lib/lzo/lzo1x_decompress_safe.c |  75 ++++++++++++++++--------
 lib/lzo/lzodefs.h               |  12 +++-
 5 files changed, 181 insertions(+), 43 deletions(-)

diff --git a/Documentation/lzo.txt b/Documentation/lzo.txt
index 6fa6a93d0949..306c60344ca7 100644
--- a/Documentation/lzo.txt
+++ b/Documentation/lzo.txt
@@ -78,16 +78,30 @@ Description
      is an implementation design choice independent on the algorithm or
      encoding.
 
+Versions
+
+0: Original version
+1: LZO-RLE
+
+Version 1 of LZO implements an extension to encode runs of zeros using run
+length encoding. This improves speed for data with many zeros, which is a
+common case for zram. This modifies the bitstream in a backwards compatible way
+(v1 can correctly decompress v0 compressed data, but v0 cannot read v1 data).
+
 Byte sequences
 ==============
 
   First byte encoding::
 
-      0..17   : follow regular instruction encoding, see below. It is worth
-                noting that codes 16 and 17 will represent a block copy from
-                the dictionary which is empty, and that they will always be
+      0..16   : follow regular instruction encoding, see below. It is worth
+                noting that code 16 will represent a block copy from the
+                dictionary which is empty, and that it will always be
                 invalid at this place.
 
+      17      : bitstream version. If the first byte is 17, the next byte
+                gives the bitstream version. If the first byte is not 17,
+                the bitstream version is 0.
+
       18..21  : copy 0..3 literals
                 state = (byte - 17) = 0..3  [ copy <state> literals ]
                 skip byte
@@ -140,6 +154,11 @@ Byte sequences
            state = S (copy S literals after this block)
            End of stream is reached if distance == 16384
 
+        In version 1, this instruction is also used to encode a run of zeros if
+        distance = 0xbfff, i.e. H = 1 and the D bits are all 1.
+           In this case, it is followed by a fourth byte, X.
+           run length = ((X << 3) | (0 0 0 0 0 L L L)) + 4.
+
       0 0 1 L L L L L  (32..63)
            Copy of small block within 16kB distance (preferably less than 34B)
            length = 2 + (L ?: 31 + (zero_bytes * 255) + non_zero_byte)
@@ -165,7 +184,9 @@ Authors
 =======
 
   This document was written by Willy Tarreau <w@1wt.eu> on 2014/07/19 during an
-  analysis of the decompression code available in Linux 3.16-rc5. The code is
-  tricky, it is possible that this document contains mistakes or that a few
-  corner cases were overlooked. In any case, please report any doubt, fix, or
-  proposed updates to the author(s) so that the document can be updated.
+  analysis of the decompression code available in Linux 3.16-rc5, and updated
+  by Dave Rodgman <dave.rodgman@arm.com> on 2018/10/30 to introduce run-length
+  encoding. The code is tricky, it is possible that this document contains
+  mistakes or that a few corner cases were overlooked. In any case, please
+  report any doubt, fix, or proposed updates to the author(s) so that the
+  document can be updated.
diff --git a/include/linux/lzo.h b/include/linux/lzo.h
index 2ae27cb89927..547a86c71e1b 100644
--- a/include/linux/lzo.h
+++ b/include/linux/lzo.h
@@ -18,7 +18,7 @@
 #define LZO1X_1_MEM_COMPRESS	(8192 * sizeof(unsigned short))
 #define LZO1X_MEM_COMPRESS	LZO1X_1_MEM_COMPRESS
 
-#define lzo1x_worst_compress(x) ((x) + ((x) / 16) + 64 + 3)
+#define lzo1x_worst_compress(x) ((x) + ((x) / 16) + 64 + 3 + 2)
 
 /* This requires 'wrkmem' of size LZO1X_1_MEM_COMPRESS */
 int lzo1x_1_compress(const unsigned char *src, size_t src_len,
diff --git a/lib/lzo/lzo1x_compress.c b/lib/lzo/lzo1x_compress.c
index 236eb21167b5..89cd561201ff 100644
--- a/lib/lzo/lzo1x_compress.c
+++ b/lib/lzo/lzo1x_compress.c
@@ -20,7 +20,7 @@
 static noinline size_t
 lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 		    unsigned char *out, size_t *out_len,
-		    size_t ti, void *wrkmem)
+		    size_t ti, void *wrkmem, signed char *state_offset)
 {
 	const unsigned char *ip;
 	unsigned char *op;
@@ -35,27 +35,85 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 	ip += ti < 4 ? 4 - ti : 0;
 
 	for (;;) {
-		const unsigned char *m_pos;
+		const unsigned char *m_pos = NULL;
 		size_t t, m_len, m_off;
 		u32 dv;
+		u32 run_length = 0;
 literal:
 		ip += 1 + ((ip - ii) >> 5);
 next:
 		if (unlikely(ip >= ip_end))
 			break;
 		dv = get_unaligned_le32(ip);
-		t = ((dv * 0x1824429d) >> (32 - D_BITS)) & D_MASK;
-		m_pos = in + dict[t];
-		dict[t] = (lzo_dict_t) (ip - in);
-		if (unlikely(dv != get_unaligned_le32(m_pos)))
-			goto literal;
+
+		if (dv == 0) {
+			const unsigned char *ir = ip + 4;
+			const unsigned char *limit = ip_end
+				< (ip + MAX_ZERO_RUN_LENGTH + 1)
+				? ip_end : ip + MAX_ZERO_RUN_LENGTH + 1;
+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && \
+	defined(LZO_FAST_64BIT_MEMORY_ACCESS)
+			u64 dv64;
+
+			for (; (ir + 32) <= limit; ir += 32) {
+				dv64 = get_unaligned((u64 *)ir);
+				dv64 |= get_unaligned((u64 *)ir + 1);
+				dv64 |= get_unaligned((u64 *)ir + 2);
+				dv64 |= get_unaligned((u64 *)ir + 3);
+				if (dv64)
+					break;
+			}
+			for (; (ir + 8) <= limit; ir += 8) {
+				dv64 = get_unaligned((u64 *)ir);
+				if (dv64) {
+#  if defined(__LITTLE_ENDIAN)
+					ir += __builtin_ctzll(dv64) >> 3;
+#  elif defined(__BIG_ENDIAN)
+					ir += __builtin_clzll(dv64) >> 3;
+#  else
+#    error "missing endian definition"
+#  endif
+					break;
+				}
+			}
+#else
+			while ((ir < (const unsigned char *)
+					ALIGN((uintptr_t)ir, 4)) &&
+					(ir < limit) && (*ir == 0))
+				ir++;
+			for (; (ir + 4) <= limit; ir += 4) {
+				dv = *((u32 *)ir);
+				if (dv) {
+#  if defined(__LITTLE_ENDIAN)
+					ir += __builtin_ctz(dv) >> 3;
+#  elif defined(__BIG_ENDIAN)
+					ir += __builtin_clz(dv) >> 3;
+#  else
+#    error "missing endian definition"
+#  endif
+					break;
+				}
+			}
+#endif
+			while (likely(ir < limit) && unlikely(*ir == 0))
+				ir++;
+			run_length = ir - ip;
+			if (run_length > MAX_ZERO_RUN_LENGTH)
+				run_length = MAX_ZERO_RUN_LENGTH;
+		} else {
+			t = ((dv * 0x1824429d) >> (32 - D_BITS)) & D_MASK;
+			m_pos = in + dict[t];
+			dict[t] = (lzo_dict_t) (ip - in);
+			if (unlikely(dv != get_unaligned_le32(m_pos)))
+				goto literal;
+		}
 
 		ii -= ti;
 		ti = 0;
 		t = ip - ii;
 		if (t != 0) {
 			if (t <= 3) {
-				op[-2] |= t;
+				op[*state_offset] |= t;
 				COPY4(op, ii);
 				op += t;
 			} else if (t <= 16) {
@@ -88,6 +146,17 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 			}
 		}
 
+		if (unlikely(run_length)) {
+			ip += run_length;
+			run_length -= MIN_ZERO_RUN_LENGTH;
+			put_unaligned_le32((run_length << 21) | 0xfffc18
+					   | (run_length & 0x7), op);
+			op += 4;
+			run_length = 0;
+			*state_offset = -3;
+			goto finished_writing_instruction;
+		}
+
 		m_len = 4;
 		{
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && defined(LZO_USE_CTZ64)
@@ -170,7 +239,6 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 
 		m_off = ip - m_pos;
 		ip += m_len;
-		ii = ip;
 		if (m_len <= M2_MAX_LEN && m_off <= M2_MAX_OFFSET) {
 			m_off -= 1;
 			*op++ = (((m_len - 1) << 5) | ((m_off & 7) << 2));
@@ -207,6 +275,9 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 			*op++ = (m_off << 2);
 			*op++ = (m_off >> 6);
 		}
+		*state_offset = -2;
+finished_writing_instruction:
+		ii = ip;
 		goto next;
 	}
 	*out_len = op - out;
@@ -221,6 +292,12 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len,
 	unsigned char *op = out;
 	size_t l = in_len;
 	size_t t = 0;
+	signed char state_offset = -2;
+
+	// LZO v0 will never write 17 as first byte,
+	// so this is used to version the bitstream
+	*op++ = 17;
+	*op++ = LZO_VERSION;
 
 	while (l > 20) {
 		size_t ll = l <= (M4_MAX_OFFSET + 1) ? l : (M4_MAX_OFFSET + 1);
@@ -229,7 +306,8 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len,
 			break;
 		BUILD_BUG_ON(D_SIZE * sizeof(lzo_dict_t) > LZO1X_1_MEM_COMPRESS);
 		memset(wrkmem, 0, D_SIZE * sizeof(lzo_dict_t));
-		t = lzo1x_1_do_compress(ip, ll, op, out_len, t, wrkmem);
+		t = lzo1x_1_do_compress(ip, ll, op, out_len,
+					t, wrkmem, &state_offset);
 		ip += ll;
 		op += *out_len;
 		l  -= ll;
@@ -242,7 +320,7 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len,
 		if (op == out && t <= 238) {
 			*op++ = (17 + t);
 		} else if (t <= 3) {
-			op[-2] |= t;
+			op[state_offset] |= t;
 		} else if (t <= 18) {
 			*op++ = (t - 3);
 		} else {
diff --git a/lib/lzo/lzo1x_decompress_safe.c b/lib/lzo/lzo1x_decompress_safe.c
index a1c387f6afba..6d2600ea3b55 100644
--- a/lib/lzo/lzo1x_decompress_safe.c
+++ b/lib/lzo/lzo1x_decompress_safe.c
@@ -46,11 +46,23 @@ int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
 	const unsigned char * const ip_end = in + in_len;
 	unsigned char * const op_end = out + *out_len;
 
+	unsigned char bitstream_version;
+
 	op = out;
 	ip = in;
 
 	if (unlikely(in_len < 3))
 		goto input_overrun;
+
+	if (likely(*ip == 17)) {
+		bitstream_version = ip[1];
+		ip += 2;
+		if (unlikely(in_len < 5))
+			goto input_overrun;
+	} else {
+		bitstream_version = 0;
+	}
+
 	if (*ip > 17) {
 		t = *ip++ - 17;
 		if (t < 4) {
@@ -154,32 +166,49 @@ int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
 			m_pos -= next >> 2;
 			next &= 3;
 		} else {
-			m_pos = op;
-			m_pos -= (t & 8) << 11;
-			t = (t & 7) + (3 - 1);
-			if (unlikely(t == 2)) {
-				size_t offset;
-				const unsigned char *ip_last = ip;
+			NEED_IP(2);
+			next = get_unaligned_le16(ip);
+			if (((next & 0xfffc) == 0xfffc) &&
+			    ((t & 0xf8) == 0x18) &&
+			    likely(bitstream_version)) {
+				NEED_IP(3);
+				t &= 7;
+				t |= ip[2] << 3;
+				t += MIN_ZERO_RUN_LENGTH;
+				NEED_OP(t);
+				memset(op, 0, t);
+				op += t;
+				next &= 3;
+				ip += 3;
+				goto match_next;
+			} else {
+				m_pos = op;
+				m_pos -= (t & 8) << 11;
+				t = (t & 7) + (3 - 1);
+				if (unlikely(t == 2)) {
+					size_t offset;
+					const unsigned char *ip_last = ip;
 
-				while (unlikely(*ip == 0)) {
-					ip++;
-					NEED_IP(1);
-				}
-				offset = ip - ip_last;
-				if (unlikely(offset > MAX_255_COUNT))
-					return LZO_E_ERROR;
+					while (unlikely(*ip == 0)) {
+						ip++;
+						NEED_IP(1);
+					}
+					offset = ip - ip_last;
+					if (unlikely(offset > MAX_255_COUNT))
+						return LZO_E_ERROR;
 
-				offset = (offset << 8) - offset;
-				t += offset + 7 + *ip++;
-				NEED_IP(2);
+					offset = (offset << 8) - offset;
+					t += offset + 7 + *ip++;
+					NEED_IP(2);
+					next = get_unaligned_le16(ip);
+				}
+				ip += 2;
+				m_pos -= next >> 2;
+				next &= 3;
+				if (m_pos == op)
+					goto eof_found;
+				m_pos -= 0x4000;
 			}
-			next = get_unaligned_le16(ip);
-			ip += 2;
-			m_pos -= next >> 2;
-			next &= 3;
-			if (m_pos == op)
-				goto eof_found;
-			m_pos -= 0x4000;
 		}
 		TEST_LB(m_pos);
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
diff --git a/lib/lzo/lzodefs.h b/lib/lzo/lzodefs.h
index fa0a45fed8c4..ac64159ee344 100644
--- a/lib/lzo/lzodefs.h
+++ b/lib/lzo/lzodefs.h
@@ -13,6 +13,12 @@
  */
 
 
+/* Version
+ * 0: original lzo version
+ * 1: lzo with support for RLE
+ */
+#define LZO_VERSION 1
+
 #define COPY4(dst, src)	\
 		put_unaligned(get_unaligned((const u32 *)(src)), (u32 *)(dst))
 #if defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
@@ -28,6 +34,7 @@
 #elif defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
 #define LZO_USE_CTZ64	1
 #define LZO_USE_CTZ32	1
+#define LZO_FAST_64BIT_MEMORY_ACCESS
 #elif defined(CONFIG_X86) || defined(CONFIG_PPC)
 #define LZO_USE_CTZ32	1
 #elif defined(CONFIG_ARM) && (__LINUX_ARM_ARCH__ >= 5)
@@ -37,7 +44,7 @@
 #define M1_MAX_OFFSET	0x0400
 #define M2_MAX_OFFSET	0x0800
 #define M3_MAX_OFFSET	0x4000
-#define M4_MAX_OFFSET	0xbfff
+#define M4_MAX_OFFSET	0xbffe
 
 #define M1_MIN_LEN	2
 #define M1_MAX_LEN	2
@@ -53,6 +60,9 @@
 #define M3_MARKER	32
 #define M4_MARKER	16
 
+#define MIN_ZERO_RUN_LENGTH	4
+#define MAX_ZERO_RUN_LENGTH	(2047 + MIN_ZERO_RUN_LENGTH)
+
 #define lzo_dict_t      unsigned short
 #define D_BITS		13
 #define D_SIZE		(1u << D_BITS)
-- 
2.17.1

[PATCH v5 2/3] lib/lzo: separate lzo-rle from lzo

[Dave Rodgman]

To prevent any issues with persistent data, separate lzo-rle
from lzo so that it is treated as a separate algorithm, and
lzo is still available.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Markus F.X.J. Oberhumer <markus@oberhumer.com>
Cc: Matt Sealey <matt.sealey@arm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <nitingupta910@gmail.com>
Cc: Richard Purdie <rpurdie@openedhand.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sonny Rao <sonnyrao@google.com>
---
 Documentation/lzo.txt      |  12 ++-
 crypto/Makefile            |   2 +-
 crypto/lzo-rle.c           | 175 +++++++++++++++++++++++++++++++++++++
 crypto/tcrypt.c            |   4 +-
 drivers/block/zram/zcomp.c |   1 +
 include/linux/lzo.h        |   4 +
 lib/lzo/lzo1x_compress.c   |  42 +++++++--
 lib/lzo/lzodefs.h          |   3 +-
 8 files changed, 226 insertions(+), 17 deletions(-)
 create mode 100644 crypto/lzo-rle.c

diff --git a/Documentation/lzo.txt b/Documentation/lzo.txt
index 306c60344ca7..f79934225d8d 100644
--- a/Documentation/lzo.txt
+++ b/Documentation/lzo.txt
@@ -88,6 +88,10 @@ length encoding. This improves speed for data with many zeros, which is a
 common case for zram. This modifies the bitstream in a backwards compatible way
 (v1 can correctly decompress v0 compressed data, but v0 cannot read v1 data).
 
+For maximum compatibility, both versions are available under different names
+(lzo and lzo-rle). Differences in the encoding are noted in this document with
+e.g.: version 1 only.
+
 Byte sequences
 ==============
 
@@ -99,8 +103,8 @@ Byte sequences
                 invalid at this place.
 
       17      : bitstream version. If the first byte is 17, the next byte
-                gives the bitstream version. If the first byte is not 17,
-                the bitstream version is 0.
+                gives the bitstream version (version 1 only). If the first byte
+                is not 17, the bitstream version is 0.
 
       18..21  : copy 0..3 literals
                 state = (byte - 17) = 0..3  [ copy <state> literals ]
@@ -154,8 +158,8 @@ Byte sequences
            state = S (copy S literals after this block)
            End of stream is reached if distance == 16384
 
-        In version 1, this instruction is also used to encode a run of zeros if
-        distance = 0xbfff, i.e. H = 1 and the D bits are all 1.
+        In version 1 only, this instruction is also used to encode a run of
+        zeros if distance = 0xbfff, i.e. H = 1 and the D bits are all 1.
            In this case, it is followed by a fourth byte, X.
            run length = ((X << 3) | (0 0 0 0 0 L L L)) + 4.
 
diff --git a/crypto/Makefile b/crypto/Makefile
index 799ed5e94606..fb5bf2a3a666 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -128,7 +128,7 @@ obj-$(CONFIG_CRYPTO_CRC32C) += crc32c_generic.o
 obj-$(CONFIG_CRYPTO_CRC32) += crc32_generic.o
 obj-$(CONFIG_CRYPTO_CRCT10DIF) += crct10dif_common.o crct10dif_generic.o
 obj-$(CONFIG_CRYPTO_AUTHENC) += authenc.o authencesn.o
-obj-$(CONFIG_CRYPTO_LZO) += lzo.o
+obj-$(CONFIG_CRYPTO_LZO) += lzo.o lzo-rle.o
 obj-$(CONFIG_CRYPTO_LZ4) += lz4.o
 obj-$(CONFIG_CRYPTO_LZ4HC) += lz4hc.o
 obj-$(CONFIG_CRYPTO_842) += 842.o
diff --git a/crypto/lzo-rle.c b/crypto/lzo-rle.c
new file mode 100644
index 000000000000..ea9c75b1db49
--- /dev/null
+++ b/crypto/lzo-rle.c
@@ -0,0 +1,175 @@
+/*
+ * Cryptographic API.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/crypto.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <linux/lzo.h>
+#include <crypto/internal/scompress.h>
+
+struct lzorle_ctx {
+	void *lzorle_comp_mem;
+};
+
+static void *lzorle_alloc_ctx(struct crypto_scomp *tfm)
+{
+	void *ctx;
+
+	ctx = kvmalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
+	if (!ctx)
+		return ERR_PTR(-ENOMEM);
+
+	return ctx;
+}
+
+static int lzorle_init(struct crypto_tfm *tfm)
+{
+	struct lzorle_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	ctx->lzorle_comp_mem = lzorle_alloc_ctx(NULL);
+	if (IS_ERR(ctx->lzorle_comp_mem))
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void lzorle_free_ctx(struct crypto_scomp *tfm, void *ctx)
+{
+	kvfree(ctx);
+}
+
+static void lzorle_exit(struct crypto_tfm *tfm)
+{
+	struct lzorle_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	lzorle_free_ctx(NULL, ctx->lzorle_comp_mem);
+}
+
+static int __lzorle_compress(const u8 *src, unsigned int slen,
+			  u8 *dst, unsigned int *dlen, void *ctx)
+{
+	size_t tmp_len = *dlen; /* size_t(ulong) <-> uint on 64 bit */
+	int err;
+
+	err = lzorle1x_1_compress(src, slen, dst, &tmp_len, ctx);
+
+	if (err != LZO_E_OK)
+		return -EINVAL;
+
+	*dlen = tmp_len;
+	return 0;
+}
+
+static int lzorle_compress(struct crypto_tfm *tfm, const u8 *src,
+			unsigned int slen, u8 *dst, unsigned int *dlen)
+{
+	struct lzorle_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	return __lzorle_compress(src, slen, dst, dlen, ctx->lzorle_comp_mem);
+}
+
+static int lzorle_scompress(struct crypto_scomp *tfm, const u8 *src,
+			 unsigned int slen, u8 *dst, unsigned int *dlen,
+			 void *ctx)
+{
+	return __lzorle_compress(src, slen, dst, dlen, ctx);
+}
+
+static int __lzorle_decompress(const u8 *src, unsigned int slen,
+			    u8 *dst, unsigned int *dlen)
+{
+	int err;
+	size_t tmp_len = *dlen; /* size_t(ulong) <-> uint on 64 bit */
+
+	err = lzo1x_decompress_safe(src, slen, dst, &tmp_len);
+
+	if (err != LZO_E_OK)
+		return -EINVAL;
+
+	*dlen = tmp_len;
+	return 0;
+}
+
+static int lzorle_decompress(struct crypto_tfm *tfm, const u8 *src,
+			  unsigned int slen, u8 *dst, unsigned int *dlen)
+{
+	return __lzorle_decompress(src, slen, dst, dlen);
+}
+
+static int lzorle_sdecompress(struct crypto_scomp *tfm, const u8 *src,
+			   unsigned int slen, u8 *dst, unsigned int *dlen,
+			   void *ctx)
+{
+	return __lzorle_decompress(src, slen, dst, dlen);
+}
+
+static struct crypto_alg alg = {
+	.cra_name		= "lzo-rle",
+	.cra_flags		= CRYPTO_ALG_TYPE_COMPRESS,
+	.cra_ctxsize		= sizeof(struct lzorle_ctx),
+	.cra_module		= THIS_MODULE,
+	.cra_init		= lzorle_init,
+	.cra_exit		= lzorle_exit,
+	.cra_u			= { .compress = {
+	.coa_compress		= lzorle_compress,
+	.coa_decompress		= lzorle_decompress } }
+};
+
+static struct scomp_alg scomp = {
+	.alloc_ctx		= lzorle_alloc_ctx,
+	.free_ctx		= lzorle_free_ctx,
+	.compress		= lzorle_scompress,
+	.decompress		= lzorle_sdecompress,
+	.base			= {
+		.cra_name	= "lzo-rle",
+		.cra_driver_name = "lzo-rle-scomp",
+		.cra_module	 = THIS_MODULE,
+	}
+};
+
+static int __init lzorle_mod_init(void)
+{
+	int ret;
+
+	ret = crypto_register_alg(&alg);
+	if (ret)
+		return ret;
+
+	ret = crypto_register_scomp(&scomp);
+	if (ret) {
+		crypto_unregister_alg(&alg);
+		return ret;
+	}
+
+	return ret;
+}
+
+static void __exit lzorle_mod_fini(void)
+{
+	crypto_unregister_alg(&alg);
+	crypto_unregister_scomp(&scomp);
+}
+
+module_init(lzorle_mod_init);
+module_exit(lzorle_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("LZO-RLE Compression Algorithm");
+MODULE_ALIAS_CRYPTO("lzo-rle");
diff --git a/crypto/tcrypt.c b/crypto/tcrypt.c
index e7fb87e114a5..1ea2d5007ff5 100644
--- a/crypto/tcrypt.c
+++ b/crypto/tcrypt.c
@@ -76,8 +76,8 @@ static char *check[] = {
 	"cast6", "arc4", "michael_mic", "deflate", "crc32c", "tea", "xtea",
 	"khazad", "wp512", "wp384", "wp256", "tnepres", "xeta",  "fcrypt",
 	"camellia", "seed", "salsa20", "rmd128", "rmd160", "rmd256", "rmd320",
-	"lzo", "cts", "sha3-224", "sha3-256", "sha3-384", "sha3-512",
-	"streebog256", "streebog512",
+	"lzo", "lzo-rle", "cts", "sha3-224", "sha3-256", "sha3-384",
+	"sha3-512", "streebog256", "streebog512",
 	NULL
 };
 
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 4ed0a78fdc09..4d9a38890965 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -20,6 +20,7 @@
 
 static const char * const backends[] = {
 	"lzo",
+	"lzo-rle",
 #if IS_ENABLED(CONFIG_CRYPTO_LZ4)
 	"lz4",
 #endif
diff --git a/include/linux/lzo.h b/include/linux/lzo.h
index 547a86c71e1b..e95c7d1092b2 100644
--- a/include/linux/lzo.h
+++ b/include/linux/lzo.h
@@ -24,6 +24,10 @@
 int lzo1x_1_compress(const unsigned char *src, size_t src_len,
 		     unsigned char *dst, size_t *dst_len, void *wrkmem);
 
+/* This requires 'wrkmem' of size LZO1X_1_MEM_COMPRESS */
+int lzorle1x_1_compress(const unsigned char *src, size_t src_len,
+		     unsigned char *dst, size_t *dst_len, void *wrkmem);
+
 /* safe decompression with overrun testing */
 int lzo1x_decompress_safe(const unsigned char *src, size_t src_len,
 			  unsigned char *dst, size_t *dst_len);
diff --git a/lib/lzo/lzo1x_compress.c b/lib/lzo/lzo1x_compress.c
index 89cd561201ff..4525fb094844 100644
--- a/lib/lzo/lzo1x_compress.c
+++ b/lib/lzo/lzo1x_compress.c
@@ -20,7 +20,8 @@
 static noinline size_t
 lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 		    unsigned char *out, size_t *out_len,
-		    size_t ti, void *wrkmem, signed char *state_offset)
+		    size_t ti, void *wrkmem, signed char *state_offset,
+		    const unsigned char bitstream_version)
 {
 	const unsigned char *ip;
 	unsigned char *op;
@@ -46,7 +47,7 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 			break;
 		dv = get_unaligned_le32(ip);
 
-		if (dv == 0) {
+		if (dv == 0 && bitstream_version) {
 			const unsigned char *ir = ip + 4;
 			const unsigned char *limit = ip_end
 				< (ip + MAX_ZERO_RUN_LENGTH + 1)
@@ -284,30 +285,36 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
 	return in_end - (ii - ti);
 }
 
-int lzo1x_1_compress(const unsigned char *in, size_t in_len,
+int lzogeneric1x_1_compress(const unsigned char *in, size_t in_len,
 		     unsigned char *out, size_t *out_len,
-		     void *wrkmem)
+		     void *wrkmem, const unsigned char bitstream_version)
 {
 	const unsigned char *ip = in;
 	unsigned char *op = out;
 	size_t l = in_len;
 	size_t t = 0;
 	signed char state_offset = -2;
+	unsigned int m4_max_offset;
 
 	// LZO v0 will never write 17 as first byte,
 	// so this is used to version the bitstream
-	*op++ = 17;
-	*op++ = LZO_VERSION;
+	if (bitstream_version > 0) {
+		*op++ = 17;
+		*op++ = bitstream_version;
+		m4_max_offset = M4_MAX_OFFSET_V1;
+	} else {
+		m4_max_offset = M4_MAX_OFFSET_V0;
+	}
 
 	while (l > 20) {
-		size_t ll = l <= (M4_MAX_OFFSET + 1) ? l : (M4_MAX_OFFSET + 1);
+		size_t ll = l <= (m4_max_offset + 1) ? l : (m4_max_offset + 1);
 		uintptr_t ll_end = (uintptr_t) ip + ll;
 		if ((ll_end + ((t + ll) >> 5)) <= ll_end)
 			break;
 		BUILD_BUG_ON(D_SIZE * sizeof(lzo_dict_t) > LZO1X_1_MEM_COMPRESS);
 		memset(wrkmem, 0, D_SIZE * sizeof(lzo_dict_t));
-		t = lzo1x_1_do_compress(ip, ll, op, out_len,
-					t, wrkmem, &state_offset);
+		t = lzo1x_1_do_compress(ip, ll, op, out_len, t, wrkmem,
+					&state_offset, bitstream_version);
 		ip += ll;
 		op += *out_len;
 		l  -= ll;
@@ -351,7 +358,24 @@ int lzo1x_1_compress(const unsigned char *in, size_t in_len,
 	*out_len = op - out;
 	return LZO_E_OK;
 }
+
+int lzo1x_1_compress(const unsigned char *in, size_t in_len,
+		     unsigned char *out, size_t *out_len,
+		     void *wrkmem)
+{
+	return lzogeneric1x_1_compress(in, in_len, out, out_len, wrkmem, 0);
+}
+
+int lzorle1x_1_compress(const unsigned char *in, size_t in_len,
+		     unsigned char *out, size_t *out_len,
+		     void *wrkmem)
+{
+	return lzogeneric1x_1_compress(in, in_len, out, out_len,
+				       wrkmem, LZO_VERSION);
+}
+
 EXPORT_SYMBOL_GPL(lzo1x_1_compress);
+EXPORT_SYMBOL_GPL(lzorle1x_1_compress);
 
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("LZO1X-1 Compressor");
diff --git a/lib/lzo/lzodefs.h b/lib/lzo/lzodefs.h
index ac64159ee344..b60851fcf6ce 100644
--- a/lib/lzo/lzodefs.h
+++ b/lib/lzo/lzodefs.h
@@ -44,7 +44,8 @@
 #define M1_MAX_OFFSET	0x0400
 #define M2_MAX_OFFSET	0x0800
 #define M3_MAX_OFFSET	0x4000
-#define M4_MAX_OFFSET	0xbffe
+#define M4_MAX_OFFSET_V0	0xbfff
+#define M4_MAX_OFFSET_V1	0xbffe
 
 #define M1_MIN_LEN	2
 #define M1_MAX_LEN	2
-- 
2.17.1

[PATCH v5 3/3] zram: default to lzo-rle instead of lzo

[Dave Rodgman]

lzo-rle gives higher performance and similar compression ratios to lzo.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
---
 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 04ca65912638..e7a5f1d1c314 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -41,7 +41,7 @@ static DEFINE_IDR(zram_index_idr);
 static DEFINE_MUTEX(zram_index_mutex);
 
 static int zram_major;
-static const char *default_compressor = "lzo";
+static const char *default_compressor = "lzo-rle";
 
 /* Module params (documentation at end) */
 static unsigned int num_devices = 1;
-- 
2.17.1

Re: [PATCH v5 0/3]: lib/lzo: run-length encoding support

[Tao Liu]

Hi Dave,

On Tue, Feb 05, 2019 at 03:59:59PM +0000, Dave Rodgman wrote:
> Hi,
> 
> Following on from the previous lzo-rle patchset:
> 
> https://lkml.org/lkml/2018/11/30/972
> 
> This patchset contains only the RLE patches, and should be applied on top of
> the non-RLE patches ( https://lkml.org/lkml/2019/2/5/366 ).
> 

Sorry for the interruption, since it is an old patchset and discussion.
I have a few questions on lzo-rle support, hope you can give me some
directions, thanks in advance!

1) Is lzo-rle suitable for userspace library? I've checked the current
userspace lzo library lzo-2.10, it seems no lzo-rle support (Please
correct me if I'm wrong). If lzo-rle have better performance in kernel,
then is it possible to implement one in userspace and gain better
performance as well?

2) Currently Yulong TANG have encountered problem that, crash utility
cannot decompress a lzo-rle compressed zram since kernel 5.1 [1], since
there is no lzo-rle support for current lzo library, crash have to
import the kernel source code directly into crash, which is not good for
crash utility code maintainance. It will be better if we can update lzo
library with lzo-rle support. I guess not only crash, but also other
kernel debugging tools running in userspace such as drgn may also need
this feature.

Do you have any suggestions on for these?

[1]: https://www.mail-archive.com/devel@lists.crash-utility.osci.io/msg00475.html

Thanks,
Tao Liu 


> 
> Previously, some questions were raised around the RLE patches. I've done some
> additional benchmarking to answer these questions. In short:
> 
>  - RLE offers significant additional performance (data-dependent)
>  - I didn't measure any regressions that were clearly outside the noise
> 
> 
> One concern with this patchset was around performance - specifically, measuring
> RLE impact separately from Matt Sealey's patches (CTZ & fast copy). I have done
> some additional benchmarking which I hope clarifies the benefits of each part
> of the patchset.
> 
> Firstly, I've captured some memory via /dev/fmem from a Chromebook with many
> tabs open which is starting to swap, and then split this into 4178 4k pages.
> I've excluded the all-zero pages (as zram does), and also the no-zero pages
> (which won't tell us anything about RLE performance). This should give a
> realistic test dataset for zram. What I found was that the data is VERY
> bimodal: 44% of pages in this dataset contain 5% or fewer zeros, and 44%
> contain over 90% zeros (30% if you include the no-zero pages). This supports
> the idea of special-casing zeros in zram.
> 
> Next, I've benchmarked four variants of lzo on these pages (on 64-bit Arm at
> max frequency): baseline LZO; baseline + Matt Sealey's patches (aka MS);
> baseline + RLE only; baseline + MS + RLE. Numbers are for weighted roundtrip
> throughput (the weighting reflects that zram does more compression than
> decompression).
> 
> https://drive.google.com/file/d/1VLtLjRVxgUNuWFOxaGPwJYhl_hMQXpHe/view?usp=sharing
> 
> Matt's patches help in all cases for Arm (and no effect on Intel), as expected.
> 
> RLE also behaves as expected: with few zeros present, it makes no difference;
> above ~75%, it gives a good improvement (50 - 300 MB/s on top of the benefit
> from Matt's patches).
> 
> Best performance is seen with both MS and RLE patches.
> 
> Finally, I have benchmarked the same dataset on an x86-64 device. Here, the
> MS patches make no difference (as expected); RLE helps, similarly as on Arm.
> There were no definite regressions; allowing for observational error, 0.1%
> (3/4178) of cases had a regression > 1 standard deviation, of which the largest
> was 4.6% (1.2 standard deviations). I think this is probably within the noise.
> 
> https://drive.google.com/file/d/1xCUVwmiGD0heEMx5gcVEmLBI4eLaageV/view?usp=sharing
> 
> One point to note is that the graphs show RLE appears to help very slightly
> with no zeros present! This is because the extra code causes the clang
> optimiser to change code layout in a way that happens to have a significant
> benefit. Taking baseline LZO and adding a do-nothing line like
> "__builtin_prefetch(out_len);" immediately before the "goto next" has the same
> effect. So this is a real, but basically spurious effect - it's small enough
> not to upset the overall findings.
> 
> Dave
> 
> 

Re: [PATCH v5 0/3]: lib/lzo: run-length encoding support

[Tao Liu]

On Fri, Mar 8, 2024 at 8:32 PM Dave Rodgman <dave.rodgman@arm.com> wrote:
>
> Hi Tao,
>
>
> I don’t see any reason for the upstream LZO library not to pick up the lzo-rle algorithm from the kernel, and I would expect the same performance benefit in userspace. This is really a question for Markus (the owner/maintainer of that library).
>
Hi Markus,

Is it possible to port the lzo-rle algorithm to the lzo library, so
userspace programs such as crash-utility or drgn can use it to
decompress the kernel data? Thanks in advance!

>
> I think the simplest short-term option would be to pull in the lzo library as source into crash-utility, and carry a patch against it to add support for lzo-rle.

Hi Dave,

Thanks for the suggestion! I agree with your short-term option, this
is what we are planning to do for now. If lzo-rle has been integrated
into the lzo library, we can then delete the patch from crash-utility
code.

Thanks,
Tao Liu

>
>
> Dave
>
>
> From: Tao Liu <ltao@redhat.com>
> Date: Friday, 8 March 2024 at 03:26
> To: Dave Rodgman <dave.rodgman@arm.com>
> Cc: linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>, Matt Sealey <Matt.Sealey@arm.com>, davem@davemloft.net <davem@davemloft.net>, gregkh@linuxfoundation.org <gregkh@linuxfoundation.org>, herbert@gondor.apana.org.au <herbert@gondor.apana.org.au>, markus@oberhumer.com <markus@oberhumer.com>, minchan@kernel.org <minchan@kernel.org>, nitingupta910@gmail.com <nitingupta910@gmail.com>, rpurdie@openedhand.com <rpurdie@openedhand.com>, sergey.senozhatsky.work@gmail.com <sergey.senozhatsky.work@gmail.com>, sonnyrao@google.com <sonnyrao@google.com>, akpm@linux-foundation.org <akpm@linux-foundation.org>, sfr@canb.auug.org.au <sfr@canb.auug.org.au>, nd <nd@arm.com>
> Subject: Re: [PATCH v5 0/3]: lib/lzo: run-length encoding support
>
> Hi Dave,
>
> On Tue, Feb 05, 2019 at 03:59:59PM +0000, Dave Rodgman wrote:
> > Hi,
> >
> > Following on from the previous lzo-rle patchset:
> >
> > https://lkml.org/lkml/2018/11/30/972
> >
> > This patchset contains only the RLE patches, and should be applied on top of
> > the non-RLE patches ( https://lkml.org/lkml/2019/2/5/366 ).
> >
>
> Sorry for the interruption, since it is an old patchset and discussion.
> I have a few questions on lzo-rle support, hope you can give me some
> directions, thanks in advance!
>
> 1) Is lzo-rle suitable for userspace library? I've checked the current
> userspace lzo library lzo-2.10, it seems no lzo-rle support (Please
> correct me if I'm wrong). If lzo-rle have better performance in kernel,
> then is it possible to implement one in userspace and gain better
> performance as well?
>
> 2) Currently Yulong TANG have encountered problem that, crash utility
> cannot decompress a lzo-rle compressed zram since kernel 5.1 [1], since
> there is no lzo-rle support for current lzo library, crash have to
> import the kernel source code directly into crash, which is not good for
> crash utility code maintainance. It will be better if we can update lzo
> library with lzo-rle support. I guess not only crash, but also other
> kernel debugging tools running in userspace such as drgn may also need
> this feature.
>
> Do you have any suggestions on for these?
>
> [1]: https://www.mail-archive.com/devel@lists.crash-utility.osci.io/msg00475.html
>
>
> Thanks,
> Tao Liu
>
>
> >
> > Previously, some questions were raised around the RLE patches. I've done some
> > additional benchmarking to answer these questions. In short:
> >
> >  - RLE offers significant additional performance (data-dependent)
> >  - I didn't measure any regressions that were clearly outside the noise
> >
> >
> > One concern with this patchset was around performance - specifically, measuring
> > RLE impact separately from Matt Sealey's patches (CTZ & fast copy). I have done
> > some additional benchmarking which I hope clarifies the benefits of each part
> > of the patchset.
> >
> > Firstly, I've captured some memory via /dev/fmem from a Chromebook with many
> > tabs open which is starting to swap, and then split this into 4178 4k pages.
> > I've excluded the all-zero pages (as zram does), and also the no-zero pages
> > (which won't tell us anything about RLE performance). This should give a
> > realistic test dataset for zram. What I found was that the data is VERY
> > bimodal: 44% of pages in this dataset contain 5% or fewer zeros, and 44%
> > contain over 90% zeros (30% if you include the no-zero pages). This supports
> > the idea of special-casing zeros in zram.
> >
> > Next, I've benchmarked four variants of lzo on these pages (on 64-bit Arm at
> > max frequency): baseline LZO; baseline + Matt Sealey's patches (aka MS);
> > baseline + RLE only; baseline + MS + RLE. Numbers are for weighted roundtrip
> > throughput (the weighting reflects that zram does more compression than
> > decompression).
> >
> > https://drive.google.com/file/d/1VLtLjRVxgUNuWFOxaGPwJYhl_hMQXpHe/view?usp=sharing
> >
> > Matt's patches help in all cases for Arm (and no effect on Intel), as expected.
> >
> > RLE also behaves as expected: with few zeros present, it makes no difference;
> > above ~75%, it gives a good improvement (50 - 300 MB/s on top of the benefit
> > from Matt's patches).
> >
> > Best performance is seen with both MS and RLE patches.
> >
> > Finally, I have benchmarked the same dataset on an x86-64 device. Here, the
> > MS patches make no difference (as expected); RLE helps, similarly as on Arm.
> > There were no definite regressions; allowing for observational error, 0.1%
> > (3/4178) of cases had a regression > 1 standard deviation, of which the largest
> > was 4.6% (1.2 standard deviations). I think this is probably within the noise.
> >
> > https://drive.google.com/file/d/1xCUVwmiGD0heEMx5gcVEmLBI4eLaageV/view?usp=sharing
> >
> > One point to note is that the graphs show RLE appears to help very slightly
> > with no zeros present! This is because the extra code causes the clang
> > optimiser to change code layout in a way that happens to have a significant
> > benefit. Taking baseline LZO and adding a do-nothing line like
> > "__builtin_prefetch(out_len);" immediately before the "goto next" has the same
> > effect. So this is a real, but basically spurious effect - it's small enough
> > not to upset the overall findings.
> >
> > Dave
> >
> >