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Merge pull request #1411 from facebook/prefetch_dict

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Improves decompression speed when using cold dictionary
This commit is contained in:
Yann Collet
2018-11-09 11:31:35 -08:00
committed by GitHub
parent 1b4a9c518b 483759a3de
commit 7b0c551bff
5 changed files with 21 additions and 25 deletions
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lib/decompress/zstd_ddict.c
-1
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@@ -15,7 +15,6 @@
* Dependencies
*********************************************************/
#include <string.h> /* memcpy, memmove, memset */
#include "compiler.h" /* prefetch */
#include "cpu.h" /* bmi2 */
#include "mem.h" /* low level memory routines */
#define FSE_STATIC_LINKING_ONLY
lib/decompress/zstd_decompress.c
-1
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@@ -56,7 +56,6 @@
* Dependencies
*********************************************************/
#include <string.h> /* memcpy, memmove, memset */
#include "compiler.h" /* prefetch */
#include "cpu.h" /* bmi2 */
#include "mem.h" /* low level memory routines */
#define FSE_STATIC_LINKING_ONLY
lib/decompress/zstd_decompress_block.c
+13 -18
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@@ -507,16 +507,6 @@ size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr,
}
}
/* prefetch dictionary content */
if (dctx->ddictIsCold) {
size_t const dictSize = (const char*)dctx->prefixStart - (const char*)dctx->virtualStart;
size_t const psmin = MIN(dictSize, (size_t)(64*nbSeq) /* heuristic */ );
size_t const pSize = MIN(psmin, 128 KB /* protection */ );
const void* const pStart = (const char*)dctx->dictEnd - pSize;
PREFETCH_AREA(pStart, pSize);
dctx->ddictIsCold = 0;
}
return ip-istart;
}
@@ -1046,6 +1036,7 @@ ZSTD_decompressSequencesLong_body(
/* prepare in advance */
for (seqNb=0; (BIT_reloadDStream(&seqState.DStream) <= BIT_DStream_completed) && (seqNb<seqAdvance); seqNb++) {
sequences[seqNb] = ZSTD_decodeSequenceLong(&seqState, isLongOffset);
PREFETCH_L1(sequences[seqNb].match); PREFETCH_L1(sequences[seqNb].match + sequences[seqNb].matchLength - 1); /* note : it's safe to invoke PREFETCH() on any memory address, including invalid ones */
}
if (seqNb<seqAdvance) return ERROR(corruption_detected);
@@ -1070,9 +1061,6 @@ ZSTD_decompressSequencesLong_body(
/* save reps for next block */
{ U32 i; for (i=0; i<ZSTD_REP_NUM; i++) dctx->entropy.rep[i] = (U32)(seqState.prevOffset[i]); }
#undef STORED_SEQS
#undef STORED_SEQS_MASK
#undef ADVANCED_SEQS
}
/* last literal segment */
@@ -1213,20 +1201,27 @@ ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx,
}
/* Build Decoding Tables */
{ int nbSeq;
{ int usePrefetchDecoder = dctx->ddictIsCold;
int nbSeq;
size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, srcSize);
if (ZSTD_isError(seqHSize)) return seqHSize;
ip += seqHSize;
srcSize -= seqHSize;
if ( (!frame || (dctx->fParams.windowSize > (1<<24)))
&& (nbSeq>0) ) { /* could probably use a larger nbSeq limit */
if ( !usePrefetchDecoder
&& (!frame || (dctx->fParams.windowSize > (1<<24)))
&& (nbSeq>ADVANCED_SEQS) ) { /* could probably use a larger nbSeq limit */
U32 const shareLongOffsets = ZSTD_getLongOffsetsShare(dctx->OFTptr);
U32 const minShare = MEM_64bits() ? 7 : 20; /* heuristic values, correspond to 2.73% and 7.81% */
if (shareLongOffsets >= minShare)
return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset);
usePrefetchDecoder = (shareLongOffsets >= minShare);
}
dctx->ddictIsCold = 0;
if (usePrefetchDecoder)
return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset);
/* else */
return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset);
}
}