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Merge pull request #2069 from bimbashrestha/doversize

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[memory opt] Downsize decompression buffers when large for too long
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Bimba Shrestha 2020-04-06 16:06:37 -05:00 committed by GitHub
commit 2847d1a606
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5 changed files with 101 additions and 34 deletions
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10
lib/common/zstd_internal.h
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@ -248,6 +248,16 @@ void ZSTD_wildcopy(void* dst, const void* src, ptrdiff_t length, ZSTD_overlap_e
}
}
/* define "workspace is too large" as this number of times larger than needed */
#define ZSTD_WORKSPACETOOLARGE_FACTOR 3
/* when workspace is continuously too large
* during at least this number of times,
* context's memory usage is considered wasteful,
* because it's sized to handle a worst case scenario which rarely happens.
* In which case, resize it down to free some memory */
#define ZSTD_WORKSPACETOOLARGE_MAXDURATION 128
/*-*******************************************
* Private declarations

10
lib/compress/zstd_cwksp.h
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@ -24,16 +24,6 @@ extern "C" {
* Constants
***************************************/
/* define "workspace is too large" as this number of times larger than needed */
#define ZSTD_WORKSPACETOOLARGE_FACTOR 3
/* when workspace is continuously too large
* during at least this number of times,
* context's memory usage is considered wasteful,
* because it's sized to handle a worst case scenario which rarely happens.
* In which case, resize it down to free some memory */
#define ZSTD_WORKSPACETOOLARGE_MAXDURATION 128
/* Since the workspace is effectively its own little malloc implementation /
* arena, when we run under ASAN, we should similarly insert redzones between
* each internal element of the workspace, so ASAN will catch overruns that

28
lib/decompress/zstd_decompress.c
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@ -111,6 +111,7 @@ static void ZSTD_initDCtx_internal(ZSTD_DCtx* dctx)
dctx->legacyContext = NULL;
dctx->previousLegacyVersion = 0;
dctx->noForwardProgress = 0;
dctx->oversizedDuration = 0;
dctx->bmi2 = ZSTD_cpuid_bmi2(ZSTD_cpuid());
}
@ -1507,6 +1508,23 @@ MEM_STATIC size_t ZSTD_limitCopy(void* dst, size_t dstCapacity, const void* src,
return length;
}
static int ZSTD_DCtx_isOverflow(ZSTD_DStream* zds, size_t const neededInBuffSize, size_t const neededOutBuffSize)
{
return (zds->inBuffSize + zds->outBuffSize) >= (neededInBuffSize + neededOutBuffSize) * ZSTD_WORKSPACETOOLARGE_FACTOR;
}
static void ZSTD_DCtx_updateOversizedDuration(ZSTD_DStream* zds, size_t const neededInBuffSize, size_t const neededOutBuffSize)
{
if (ZSTD_DCtx_isOverflow(zds, neededInBuffSize, neededOutBuffSize))
zds->oversizedDuration++;
else
zds->oversizedDuration = 0;
}
static int ZSTD_DCtx_isOversizedTooLong(ZSTD_DStream* zds)
{
return zds->oversizedDuration >= ZSTD_WORKSPACETOOLARGE_MAXDURATION;
}
size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input)
{
@ -1636,7 +1654,13 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
/* Adapt buffer sizes to frame header instructions */
{ size_t const neededInBuffSize = MAX(zds->fParams.blockSizeMax, 4 /* frame checksum */);
size_t const neededOutBuffSize = ZSTD_decodingBufferSize_min(zds->fParams.windowSize, zds->fParams.frameContentSize);
if ((zds->inBuffSize < neededInBuffSize) || (zds->outBuffSize < neededOutBuffSize)) {
ZSTD_DCtx_updateOversizedDuration(zds, neededInBuffSize, neededOutBuffSize);
{ int const tooSmall = (zds->inBuffSize < neededInBuffSize) || (zds->outBuffSize < neededOutBuffSize);
int const tooLarge = ZSTD_DCtx_isOversizedTooLong(zds);
if (tooSmall || tooLarge) {
size_t const bufferSize = neededInBuffSize + neededOutBuffSize;
DEBUGLOG(4, "inBuff : from %u to %u",
(U32)zds->inBuffSize, (U32)neededInBuffSize);
@ -1658,7 +1682,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
zds->inBuffSize = neededInBuffSize;
zds->outBuff = zds->inBuff + zds->inBuffSize;
zds->outBuffSize = neededOutBuffSize;
} }
} } }
zds->streamStage = zdss_read;
/* fall-through */

2
lib/decompress/zstd_decompress_internal.h
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@ -151,6 +151,8 @@ struct ZSTD_DCtx_s
/* workspace */
BYTE litBuffer[ZSTD_BLOCKSIZE_MAX + WILDCOPY_OVERLENGTH];
BYTE headerBuffer[ZSTD_FRAMEHEADERSIZE_MAX];
size_t oversizedDuration;
}; /* typedef'd to ZSTD_DCtx within "zstd.h" */

43
tests/fuzzer.c
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@ -525,7 +525,48 @@ static int basicUnitTests(U32 const seed, double compressibility)
}
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3d: superblock uncompressible data, too many nocompress superblocks : ", testNb++)
DISPLAYLEVEL(3, "test%3d: check DCtx size is reduced after many oversized calls : ", testNb++);
{
size_t const largeFrameSrcSize = 200;
size_t const smallFrameSrcSize = 10;
size_t const nbFrames = 256;
size_t i = 0, consumed = 0, produced = 0, prevDCtxSize = 0;
int sizeReduced = 0;
BYTE* const dst = (BYTE*)compressedBuffer;
ZSTD_DCtx* dctx = ZSTD_createDCtx();
/* create a large frame and then a bunch of small frames */
size_t srcSize = ZSTD_compress((void*)dst,
compressedBufferSize, CNBuffer, largeFrameSrcSize, 3);
for (i = 0; i < nbFrames; i++)
srcSize += ZSTD_compress((void*)(dst + srcSize),
compressedBufferSize - srcSize, CNBuffer,
smallFrameSrcSize, 3);
/* decompressStream and make sure that dctx size was reduced at least once */
while (consumed < srcSize) {
ZSTD_inBuffer in = {(void*)(dst + consumed), MIN(1, srcSize - consumed), 0};
ZSTD_outBuffer out = {(BYTE*)CNBuffer + produced, CNBuffSize - produced, 0};
ZSTD_decompressStream(dctx, &out, &in);
consumed += in.pos;
produced += out.pos;
/* success! size was reduced from the previous frame */
if (prevDCtxSize > ZSTD_sizeof_DCtx(dctx))
sizeReduced = 1;
prevDCtxSize = ZSTD_sizeof_DCtx(dctx);
}
assert(sizeReduced);
ZSTD_freeDCtx(dctx);
}
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3d: superblock uncompressible data, too many nocompress superblocks : ", testNb++);
{
ZSTD_CCtx* const cctx = ZSTD_createCCtx();
const BYTE* src = (BYTE*)CNBuffer; BYTE* dst = (BYTE*)compressedBuffer;