ddidderr/zstd-rs
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XP: add a pre-splitter

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instead of ingesting only full blocks, make an analysis of data, and infer where to split.
This commit is contained in:
Yann Collet
2024-10-23 11:50:56 -07:00
parent dfaf5fafb9
commit a5bce4ae84
3 changed files with 188 additions and 8 deletions
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lib/compress/zstd_compress.c
+23 -8
View File
@@ -883,7 +883,7 @@ size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* CCtxParams,
value = ZSTDMT_JOBSIZE_MIN;
FORWARD_IF_ERROR(ZSTD_cParam_clampBounds(param, &value), "");
assert(value >= 0);
CCtxParams->jobSize = value;
CCtxParams->jobSize = (size_t)value;
return CCtxParams->jobSize;
#endif
@@ -1002,7 +1002,8 @@ size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* CCtxParams,
case ZSTD_c_maxBlockSize:
if (value!=0) /* 0 ==> default */
BOUNDCHECK(ZSTD_c_maxBlockSize, value);
CCtxParams->maxBlockSize = value;
assert(value>=0);
CCtxParams->maxBlockSize = (size_t)value;
return CCtxParams->maxBlockSize;
case ZSTD_c_searchForExternalRepcodes:
@@ -2444,7 +2445,8 @@ static size_t ZSTD_resetCCtx_byCopyingCDict(ZSTD_CCtx* cctx,
}
/* Zero the hashTable3, since the cdict never fills it */
{ int const h3log = cctx->blockState.matchState.hashLog3;
assert(cctx->blockState.matchState.hashLog3 <= 31);
{ U32 const h3log = cctx->blockState.matchState.hashLog3;
size_t const h3Size = h3log ? ((size_t)1 << h3log) : 0;
assert(cdict->matchState.hashLog3 == 0);
ZSTD_memset(cctx->blockState.matchState.hashTable3, 0, h3Size * sizeof(U32));
@@ -4484,6 +4486,18 @@ static void ZSTD_overflowCorrectIfNeeded(ZSTD_matchState_t* ms,
}
}
#include "zstd_preSplit.h"
static size_t ZSTD_optimalBlockSize(const void* src, size_t srcSize, size_t blockSizeMax, ZSTD_strategy strat)
{
if (srcSize <= 128 KB || blockSizeMax < 128 KB)
return MIN(srcSize, blockSizeMax);
(void)strat;
if (strat >= ZSTD_btlazy2)
return ZSTD_splitBlock_4k(src, srcSize, blockSizeMax);
return 92 KB;
}
/*! ZSTD_compress_frameChunk() :
* Compress a chunk of data into one or multiple blocks.
* All blocks will be terminated, all input will be consumed.
@@ -4496,7 +4510,7 @@ static size_t ZSTD_compress_frameChunk(ZSTD_CCtx* cctx,
const void* src, size_t srcSize,
U32 lastFrameChunk)
{
size_t blockSize = cctx->blockSize;
size_t blockSizeMax = cctx->blockSize;
size_t remaining = srcSize;
const BYTE* ip = (const BYTE*)src;
BYTE* const ostart = (BYTE*)dst;
@@ -4505,20 +4519,21 @@ static size_t ZSTD_compress_frameChunk(ZSTD_CCtx* cctx,
assert(cctx->appliedParams.cParams.windowLog <= ZSTD_WINDOWLOG_MAX);
DEBUGLOG(4, "ZSTD_compress_frameChunk (blockSize=%u)", (unsigned)blockSize);
DEBUGLOG(4, "ZSTD_compress_frameChunk (blockSizeMax=%u)", (unsigned)blockSizeMax);
if (cctx->appliedParams.fParams.checksumFlag && srcSize)
XXH64_update(&cctx->xxhState, src, srcSize);
while (remaining) {
ZSTD_matchState_t* const ms = &cctx->blockState.matchState;
U32 const lastBlock = lastFrameChunk & (blockSize >= remaining);
U32 const lastBlock = lastFrameChunk & (blockSizeMax >= remaining);
size_t blockSize = ZSTD_optimalBlockSize(ip, remaining, blockSizeMax, cctx->appliedParams.cParams.strategy);
assert(blockSize <= remaining);
/* TODO: See 3090. We reduced MIN_CBLOCK_SIZE from 3 to 2 so to compensate we are adding
* additional 1. We need to revisit and change this logic to be more consistent */
RETURN_ERROR_IF(dstCapacity < ZSTD_blockHeaderSize + MIN_CBLOCK_SIZE + 1,
dstSize_tooSmall,
"not enough space to store compressed block");
if (remaining < blockSize) blockSize = remaining;
ZSTD_overflowCorrectIfNeeded(
ms, &cctx->workspace, &cctx->appliedParams, ip, ip + blockSize);
@@ -5022,7 +5037,7 @@ size_t ZSTD_loadCEntropy(ZSTD_compressedBlockState_t* bs, void* workspace,
RETURN_ERROR_IF(bs->rep[u] > dictContentSize, dictionary_corrupted, "");
} } }
return dictPtr - (const BYTE*)dict;
return (size_t)(dictPtr - (const BYTE*)dict);
}
/* Dictionary format :
lib/compress/zstd_preSplit.c
+139
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@@ -0,0 +1,139 @@
/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/
#include "../common/mem.h" /* U64 */
#include "zstd_preSplit.h"
#define BLOCKSIZE_MIN 3500
#define THRESHOLD_PENALTY_RATE 16
#define THRESHOLD_BASE (THRESHOLD_PENALTY_RATE - 2)
#define THRESHOLD_PENALTY 4
#define HASHLENGTH 2
#define HASHLOG 10
#define HASHTABLESIZE (1 << HASHLOG)
#define HASHMASK (HASHTABLESIZE - 1)
#define KNUTH 0x9e3779b9
static unsigned hash2(const void *p)
{
return (U32)(MEM_read16(p)) * KNUTH >> (32 - HASHLOG);
}
/* ==================================== */
/* Global array -> for testing only !!! */
/* ==================================== */
typedef struct {
int events[HASHTABLESIZE];
S64 nbEvents;
} FingerPrint;
static FingerPrint pastEvents = {};
static FingerPrint newEvents = {};
static void initStats(void) {
memset(&pastEvents, 0, sizeof(pastEvents));
memset(&newEvents, 0, sizeof(newEvents));
}
/* ==================================== */
static void addToFingerprint(FingerPrint* fp, const void* src, size_t s) {
const char* p = src;
size_t limit = s - HASHLENGTH + 1;
assert(s >= HASHLENGTH);
for (size_t n = 0; n < limit; n++) {
fp->events[hash2(p++)]++;
}
fp->nbEvents += limit;
}
static void recordFingerprint(FingerPrint *fp, const void *src, size_t s) {
memset(fp, 0, sizeof(*fp));
addToFingerprint(fp, src, s);
}
static S64 abs64(S64 i) { return (i < 0) ? -i : i; }
static S64 fpDistance(const FingerPrint *fp1, const FingerPrint *fp2) {
S64 distance = 0;
for (size_t n = 0; n < HASHTABLESIZE; n++) {
distance +=
abs64(fp1->events[n] * fp2->nbEvents - fp2->events[n] * fp1->nbEvents);
}
return distance;
}
// Compare newEvents with pastEvents
// return 1 when considered "too different"
// debug:write Deviation value in %
static int compareFingerprints(const FingerPrint *ref,
const FingerPrint *new,
int penalty)
{
if (ref->nbEvents <= BLOCKSIZE_MIN)
return 0;
{ S64 p50 = ref->nbEvents * new->nbEvents;
S64 deviation = fpDistance(ref, new);
// printf("Deviation: %.2f%% \n", (double)deviation / (double)ref * 100.);
S64 threshold = p50 * (THRESHOLD_BASE + penalty) / THRESHOLD_PENALTY_RATE;
return deviation >= threshold;
}
}
static void mergeEvents(FingerPrint *acc, const FingerPrint *new) {
for (size_t n = 0; n < HASHTABLESIZE; n++) {
acc->events[n] += new->events[n];
}
acc->nbEvents += new->nbEvents;
}
static void flushEvents(void) {
for (size_t n = 0; n < HASHTABLESIZE; n++) {
pastEvents.events[n] = newEvents.events[n];
}
pastEvents.nbEvents = newEvents.nbEvents;
memset(&newEvents, 0, sizeof(newEvents));
}
static void removeEvents(FingerPrint *acc, const FingerPrint *slice) {
for (size_t n = 0; n < HASHTABLESIZE; n++) {
assert(acc->events[n] >= slice->events[n]);
acc->events[n] -= slice->events[n];
}
acc->nbEvents -= slice->nbEvents;
}
#define CHUNKSIZE (8 << 10)
/* Note: technically, we use CHUNKSIZE, so that's 8 KB */
size_t ZSTD_splitBlock_4k(const void* src, size_t srcSize, size_t blockSizeMax)
{
const char* p = src;
int penalty = THRESHOLD_PENALTY;
size_t pos = 0;
if (srcSize <= blockSizeMax) return srcSize;
assert(blockSizeMax == (128 << 10));
initStats();
for (pos = 0; pos < blockSizeMax;) {
assert(pos <= blockSizeMax - CHUNKSIZE);
recordFingerprint(&newEvents, p + pos, CHUNKSIZE);
if (compareFingerprints(&pastEvents, &newEvents, penalty)) {
return pos;
} else {
mergeEvents(&pastEvents, &newEvents);
memset(&newEvents, 0, sizeof(newEvents));
penalty = penalty - 1 + (penalty == 0);
}
pos += CHUNKSIZE;
}
return blockSizeMax;
(void)flushEvents; (void)removeEvents;
}
lib/compress/zstd_preSplit.h
+26
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@@ -0,0 +1,26 @@
/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/
#ifndef ZSTD_PRESPLIT_H
#define ZSTD_PRESPLIT_H
#include <stddef.h> /* size_t */
#if defined (__cplusplus)
extern "C" {
#endif
size_t ZSTD_splitBlock_4k(const void* src, size_t srcSize, size_t blockSizeMax);
#if defined (__cplusplus)
}
#endif
#endif /* ZSTD_PRESPLIT_H */