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Merge pull request #3917 from facebook/targetCBlock_moreRegular

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More regular block sizes with `targetCBlockSize`
This commit is contained in:
Yann Collet
2024-02-26 15:38:00 -08:00
committed by GitHub
parent 5c5c1b0d90 8d31e8ec42
commit 34cf4c139e
1 changed files with 159 additions and 81 deletions
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lib/compress/zstd_compress_superblock.c
+159 -81
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@@ -390,7 +390,11 @@ static size_t ZSTD_estimateSubBlockSize_sequences(const BYTE* ofCodeTable,
return cSeqSizeEstimate + sequencesSectionHeaderSize; return cSeqSizeEstimate + sequencesSectionHeaderSize;
} }
static size_t ZSTD_estimateSubBlockSize(const BYTE* literals, size_t litSize, typedef struct {
size_t estLitSize;
size_t estBlockSize;
} EstimatedBlockSize;
static EstimatedBlockSize ZSTD_estimateSubBlockSize(const BYTE* literals, size_t litSize,
const BYTE* ofCodeTable, const BYTE* ofCodeTable,
const BYTE* llCodeTable, const BYTE* llCodeTable,
const BYTE* mlCodeTable, const BYTE* mlCodeTable,
@@ -398,15 +402,17 @@ static size_t ZSTD_estimateSubBlockSize(const BYTE* literals, size_t litSize,
const ZSTD_entropyCTables_t* entropy, const ZSTD_entropyCTables_t* entropy,
const ZSTD_entropyCTablesMetadata_t* entropyMetadata, const ZSTD_entropyCTablesMetadata_t* entropyMetadata,
void* workspace, size_t wkspSize, void* workspace, size_t wkspSize,
int writeLitEntropy, int writeSeqEntropy) { int writeLitEntropy, int writeSeqEntropy)
size_t cSizeEstimate = 0; {
cSizeEstimate += ZSTD_estimateSubBlockSize_literal(literals, litSize, EstimatedBlockSize ebs;
&entropy->huf, &entropyMetadata->hufMetadata, ebs.estLitSize = ZSTD_estimateSubBlockSize_literal(literals, litSize,
workspace, wkspSize, writeLitEntropy); &entropy->huf, &entropyMetadata->hufMetadata,
cSizeEstimate += ZSTD_estimateSubBlockSize_sequences(ofCodeTable, llCodeTable, mlCodeTable, workspace, wkspSize, writeLitEntropy);
ebs.estBlockSize = ZSTD_estimateSubBlockSize_sequences(ofCodeTable, llCodeTable, mlCodeTable,
nbSeq, &entropy->fse, &entropyMetadata->fseMetadata, nbSeq, &entropy->fse, &entropyMetadata->fseMetadata,
workspace, wkspSize, writeSeqEntropy); workspace, wkspSize, writeSeqEntropy);
return cSizeEstimate + ZSTD_blockHeaderSize; ebs.estBlockSize += ebs.estLitSize + ZSTD_blockHeaderSize;
return ebs;
} }
static int ZSTD_needSequenceEntropyTables(ZSTD_fseCTablesMetadata_t const* fseMetadata) static int ZSTD_needSequenceEntropyTables(ZSTD_fseCTablesMetadata_t const* fseMetadata)
@@ -427,17 +433,51 @@ static size_t countLiterals(seqStore_t const* seqStore, const seqDef* sp, size_t
for (n=0; n<seqCount; n++) { for (n=0; n<seqCount; n++) {
total += ZSTD_getSequenceLength(seqStore, sp+n).litLength; total += ZSTD_getSequenceLength(seqStore, sp+n).litLength;
} }
DEBUGLOG(5, "countLiterals for %zu sequences from %p => %zu bytes", seqCount, (const void*)sp, total); DEBUGLOG(6, "countLiterals for %zu sequences from %p => %zu bytes", seqCount, (const void*)sp, total);
return total; return total;
} }
#define BYTESCALE 256
static size_t sizeBlockSequences(const seqDef* sp, size_t nbSeqs,
size_t targetBudget, size_t avgLitCost, size_t avgSeqCost,
int firstSubBlock)
{
size_t n, budget = 0, inSize=0;
/* entropy headers */
size_t const headerSize = (size_t)firstSubBlock * 120 * BYTESCALE; /* generous estimate */
assert(firstSubBlock==0 || firstSubBlock==1);
budget += headerSize;
/* first sequence => at least one sequence*/
budget += sp[0].litLength * avgLitCost + avgSeqCost;
if (budget > targetBudget) return 1;
inSize = sp[0].litLength + (sp[0].mlBase+MINMATCH);
/* loop over sequences */
for (n=1; n<nbSeqs; n++) {
size_t currentCost = sp[n].litLength * avgLitCost + avgSeqCost;
budget += currentCost;
inSize += sp[n].litLength + (sp[n].mlBase+MINMATCH);
/* stop when sub-block budget is reached */
if ( (budget > targetBudget)
/* though continue to expand until the sub-block is deemed compressible */
&& (budget < inSize * BYTESCALE) )
break;
}
return n;
}
#define CBLOCK_TARGET_SIZE_MIN 1340 /* suitable to fit into an ethernet / wifi / 4G transport frame */
/** ZSTD_compressSubBlock_multi() : /** ZSTD_compressSubBlock_multi() :
* Breaks super-block into multiple sub-blocks and compresses them. * Breaks super-block into multiple sub-blocks and compresses them.
* Entropy will be written to the first block. * Entropy will be written into the first block.
* The following blocks will use repeat mode to compress. * The following blocks use repeat_mode to compress.
* All sub-blocks are compressed blocks (no raw or rle blocks). * Sub-blocks are all compressed, except the last one when beneficial.
* @return : compressed size of the super block (which is multiple ZSTD blocks) * @return : compressed size of the super block (which features multiple ZSTD blocks)
* Or 0 if it failed to compress. */ * or 0 if it failed to compress. */
static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr, static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
const ZSTD_compressedBlockState_t* prevCBlock, const ZSTD_compressedBlockState_t* prevCBlock,
ZSTD_compressedBlockState_t* nextCBlock, ZSTD_compressedBlockState_t* nextCBlock,
@@ -452,7 +492,6 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
const seqDef* const send = seqStorePtr->sequences; const seqDef* const send = seqStorePtr->sequences;
const seqDef* sp = sstart; /* tracks progresses within seqStorePtr->sequences */ const seqDef* sp = sstart; /* tracks progresses within seqStorePtr->sequences */
size_t const nbSeqs = (size_t)(send - sstart); size_t const nbSeqs = (size_t)(send - sstart);
size_t nbSeqsPerBlock = nbSeqs;
const BYTE* const lstart = seqStorePtr->litStart; const BYTE* const lstart = seqStorePtr->litStart;
const BYTE* const lend = seqStorePtr->lit; const BYTE* const lend = seqStorePtr->lit;
const BYTE* lp = lstart; const BYTE* lp = lstart;
@@ -465,90 +504,129 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
const BYTE* llCodePtr = seqStorePtr->llCode; const BYTE* llCodePtr = seqStorePtr->llCode;
const BYTE* mlCodePtr = seqStorePtr->mlCode; const BYTE* mlCodePtr = seqStorePtr->mlCode;
const BYTE* ofCodePtr = seqStorePtr->ofCode; const BYTE* ofCodePtr = seqStorePtr->ofCode;
size_t const minTarget = 1300; /* enforce minimum size, to reduce undesirable side effects */ size_t const minTarget = CBLOCK_TARGET_SIZE_MIN; /* enforce minimum size, to reduce undesirable side effects */
size_t const targetCBlockSize = MAX(minTarget, cctxParams->targetCBlockSize); size_t const targetCBlockSize = MAX(minTarget, cctxParams->targetCBlockSize);
int writeLitEntropy = (entropyMetadata->hufMetadata.hType == set_compressed); int writeLitEntropy = (entropyMetadata->hufMetadata.hType == set_compressed);
int writeSeqEntropy = 1; int writeSeqEntropy = 1;
size_t nbSubBlocks = 1;
DEBUGLOG(5, "ZSTD_compressSubBlock_multi (srcSize=%u, litSize=%u, nbSeq=%u)", DEBUGLOG(5, "ZSTD_compressSubBlock_multi (srcSize=%u, litSize=%u, nbSeq=%u)",
(unsigned)srcSize, (unsigned)(lend-lstart), (unsigned)(send-sstart)); (unsigned)srcSize, (unsigned)(lend-lstart), (unsigned)(send-sstart));
if (nbSeqs == 0) {
/* special case : no sequence */
nbSeqsPerBlock = 0;
nbSubBlocks = 1;
} else {
/* let's start by a general estimation for the full block */ /* let's start by a general estimation for the full block */
size_t const cBlockSizeEstimate = if (nbSeqs > 0) {
EstimatedBlockSize const ebs =
ZSTD_estimateSubBlockSize(lp, nbLiterals, ZSTD_estimateSubBlockSize(lp, nbLiterals,
ofCodePtr, llCodePtr, mlCodePtr, nbSeqs, ofCodePtr, llCodePtr, mlCodePtr, nbSeqs,
&nextCBlock->entropy, entropyMetadata, &nextCBlock->entropy, entropyMetadata,
workspace, wkspSize, workspace, wkspSize,
writeLitEntropy, writeSeqEntropy); writeLitEntropy, writeSeqEntropy);
/* quick estimation */ /* quick estimation */
nbSubBlocks = (cBlockSizeEstimate + (targetCBlockSize-1)) / targetCBlockSize; size_t const avgLitCost = nbLiterals ? (ebs.estLitSize * BYTESCALE) / nbLiterals : BYTESCALE;
assert(nbSubBlocks > 0); size_t const avgSeqCost = ((ebs.estBlockSize - ebs.estLitSize) * BYTESCALE) / nbSeqs;
if (nbSeqs > nbSubBlocks) { const size_t nbSubBlocks = MAX((ebs.estBlockSize + (targetCBlockSize/2)) / targetCBlockSize, 1);
nbSeqsPerBlock = nbSeqs / nbSubBlocks; size_t n, avgBlockBudget, blockBudgetSupp=0;
} else { avgBlockBudget = (ebs.estBlockSize * BYTESCALE) / nbSubBlocks;
nbSeqsPerBlock = 1; DEBUGLOG(5, "estimated fullblock size=%u bytes ; avgLitCost=%.2f ; avgSeqCost=%.2f ; targetCBlockSize=%u, nbSubBlocks=%u ; avgBlockBudget=%.0f bytes",
nbSubBlocks = nbSeqs; (unsigned)ebs.estBlockSize, (double)avgLitCost/BYTESCALE, (double)avgSeqCost/BYTESCALE,
(unsigned)targetCBlockSize, (unsigned)nbSubBlocks, (double)avgBlockBudget/BYTESCALE);
/* simplification: if estimates states that the full superblock doesn't compress, just bail out immediately
* this will result in the production of a single uncompressed block covering @srcSize.*/
if (ebs.estBlockSize > srcSize) return 0;
/* compress and write sub-blocks */
assert(nbSubBlocks>0);
for (n=0; n < nbSubBlocks-1; n++) {
/* determine nb of sequences for current sub-block + nbLiterals from next sequence */
size_t const seqCount = sizeBlockSequences(sp, (size_t)(send-sp),
avgBlockBudget + blockBudgetSupp, avgLitCost, avgSeqCost, n==0);
/* if reached last sequence : break to last sub-block (simplification) */
assert(seqCount <= (size_t)(send-sp));
if (sp + seqCount == send) break;
assert(seqCount > 0);
/* compress sub-block */
{ int litEntropyWritten = 0;
int seqEntropyWritten = 0;
size_t litSize = countLiterals(seqStorePtr, sp, seqCount);
const size_t decompressedSize =
ZSTD_seqDecompressedSize(seqStorePtr, sp, seqCount, litSize, 0);
size_t const cSize = ZSTD_compressSubBlock(&nextCBlock->entropy, entropyMetadata,
sp, seqCount,
lp, litSize,
llCodePtr, mlCodePtr, ofCodePtr,
cctxParams,
op, (size_t)(oend-op),
bmi2, writeLitEntropy, writeSeqEntropy,
&litEntropyWritten, &seqEntropyWritten,
0);
FORWARD_IF_ERROR(cSize, "ZSTD_compressSubBlock failed");
/* check compressibility, update state components */
if (cSize > 0 && cSize < decompressedSize) {
DEBUGLOG(5, "Committed sub-block compressing %u bytes => %u bytes",
(unsigned)decompressedSize, (unsigned)cSize);
assert(ip + decompressedSize <= iend);
ip += decompressedSize;
lp += litSize;
op += cSize;
llCodePtr += seqCount;
mlCodePtr += seqCount;
ofCodePtr += seqCount;
/* Entropy only needs to be written once */
if (litEntropyWritten) {
writeLitEntropy = 0;
}
if (seqEntropyWritten) {
writeSeqEntropy = 0;
}
sp += seqCount;
blockBudgetSupp = 0;
} }
/* otherwise : do not compress yet, coalesce current sub-block with following one */
} }
/* Note: this is very approximative. Obviously, some sub-blocks will be larger and others smaller. } /* if (nbSeqs > 0) */
* But the contract of this feature has always been approximative, so for now we'll leverage it for speed.
* It can be refined later, for closer-to-target compressed block size, if it ever matters. */
}
/* write sub-blocks */ /* write last block */
{ size_t n; DEBUGLOG(2, "Generate last sub-block: %u sequences remaining", (unsigned)(send - sp));
size_t nbSeqsToProcess = 0; { int litEntropyWritten = 0;
for (n=0; n < nbSubBlocks; n++) { int seqEntropyWritten = 0;
int const lastSubBlock = (n==nbSubBlocks-1); size_t litSize = (size_t)(lend - lp);
size_t const nbSeqsLastSubBlock = nbSeqs - (nbSubBlocks-1) * nbSeqsPerBlock; size_t seqCount = (size_t)(send - sp);
size_t nbSeqsSubBlock = lastSubBlock ? nbSeqsLastSubBlock : nbSeqsPerBlock; const size_t decompressedSize =
size_t seqCount = nbSeqsToProcess+nbSeqsSubBlock; ZSTD_seqDecompressedSize(seqStorePtr, sp, seqCount, litSize, 1);
size_t litSize = lastSubBlock ? (size_t)(lend-lp) : countLiterals(seqStorePtr, sp, seqCount); size_t const cSize = ZSTD_compressSubBlock(&nextCBlock->entropy, entropyMetadata,
int litEntropyWritten = 0; sp, seqCount,
int seqEntropyWritten = 0; lp, litSize,
const size_t decompressedSize = llCodePtr, mlCodePtr, ofCodePtr,
ZSTD_seqDecompressedSize(seqStorePtr, sp, seqCount, litSize, lastSubBlock); cctxParams,
size_t const cSize = ZSTD_compressSubBlock(&nextCBlock->entropy, entropyMetadata, op, (size_t)(oend-op),
sp, seqCount, bmi2, writeLitEntropy, writeSeqEntropy,
lp, litSize, &litEntropyWritten, &seqEntropyWritten,
llCodePtr, mlCodePtr, ofCodePtr, lastBlock);
cctxParams, FORWARD_IF_ERROR(cSize, "ZSTD_compressSubBlock failed");
op, (size_t)(oend-op),
bmi2, writeLitEntropy, writeSeqEntropy,
&litEntropyWritten, &seqEntropyWritten,
lastBlock && lastSubBlock);
nbSeqsToProcess = seqCount;
FORWARD_IF_ERROR(cSize, "ZSTD_compressSubBlock failed");
if (cSize > 0 && cSize < decompressedSize) { /* update pointers, the nb of literals borrowed from next sequence must be preserved */
DEBUGLOG(5, "Committed sub-block compressing %u bytes => %u bytes", if (cSize > 0 && cSize < decompressedSize) {
(unsigned)decompressedSize, (unsigned)cSize); DEBUGLOG(2, "Last sub-block compressed %u bytes => %u bytes",
assert(ip + decompressedSize <= iend); (unsigned)decompressedSize, (unsigned)cSize);
ip += decompressedSize; assert(ip + decompressedSize <= iend);
lp += litSize; ip += decompressedSize;
op += cSize; lp += litSize;
llCodePtr += seqCount; op += cSize;
mlCodePtr += seqCount; llCodePtr += seqCount;
ofCodePtr += seqCount; mlCodePtr += seqCount;
/* Entropy only needs to be written once */ ofCodePtr += seqCount;
if (litEntropyWritten) { /* Entropy only needs to be written once */
writeLitEntropy = 0; if (litEntropyWritten) {
} writeLitEntropy = 0;
if (seqEntropyWritten) {
writeSeqEntropy = 0;
}
sp += seqCount;
nbSeqsToProcess = 0;
} }
/* otherwise : coalesce current block with next one */ if (seqEntropyWritten) {
writeSeqEntropy = 0;
}
sp += seqCount;
} }
} }
if (writeLitEntropy) { if (writeLitEntropy) {
DEBUGLOG(5, "Literal entropy tables were never written"); DEBUGLOG(5, "Literal entropy tables were never written");
ZSTD_memcpy(&nextCBlock->entropy.huf, &prevCBlock->entropy.huf, sizeof(prevCBlock->entropy.huf)); ZSTD_memcpy(&nextCBlock->entropy.huf, &prevCBlock->entropy.huf, sizeof(prevCBlock->entropy.huf));
@@ -565,7 +643,7 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
/* some data left : last part of the block sent uncompressed */ /* some data left : last part of the block sent uncompressed */
size_t const rSize = (size_t)((iend - ip)); size_t const rSize = (size_t)((iend - ip));
size_t const cSize = ZSTD_noCompressBlock(op, (size_t)(oend - op), ip, rSize, lastBlock); size_t const cSize = ZSTD_noCompressBlock(op, (size_t)(oend - op), ip, rSize, lastBlock);
DEBUGLOG(5, "Generate last uncompressed sub-block of %u bytes", (unsigned)(rSize)); DEBUGLOG(2, "Generate last uncompressed sub-block of %u bytes", (unsigned)(rSize));
FORWARD_IF_ERROR(cSize, "ZSTD_noCompressBlock failed"); FORWARD_IF_ERROR(cSize, "ZSTD_noCompressBlock failed");
assert(cSize != 0); assert(cSize != 0);
op += cSize; op += cSize;
@@ -581,8 +659,8 @@ static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr,
} }
} }
DEBUGLOG(5, "ZSTD_compressSubBlock_multi compressed %u subBlocks: total compressed size = %u", DEBUGLOG(5, "ZSTD_compressSubBlock_multi compressed all subBlocks: total compressed size = %u",
(unsigned)nbSubBlocks, (unsigned)(op-ostart)); (unsigned)(op-ostart));
return (size_t)(op-ostart); return (size_t)(op-ostart);
} }