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split all full 128 KB blocks

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this helps make the streaming behavior more consistent,
since it does no longer depend on having more data presented on the input.

suggested by @terrelln
This commit is contained in:
Yann Collet
2024-10-23 14:18:48 -07:00
parent b68ddce818
commit 7d3e5e3ba1
1 changed files with 6 additions and 5 deletions
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lib/compress/zstd_compress.c
+6 -5
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@@ -4493,20 +4493,21 @@ static void ZSTD_overflowCorrectIfNeeded(ZSTD_matchState_t* ms,
static size_t ZSTD_optimalBlockSize(ZSTD_CCtx* cctx, const void* src, size_t srcSize, size_t blockSizeMax, ZSTD_strategy strat, S64 savings)
{
/* note: conservatively only split full blocks (128 KB) currently,
* and even then only if there is more than 128 KB input remaining.
/* note: conservatively only split full blocks (128 KB) currently.
* While it's possible to go lower, let's keep it simple for a first implementation.
* Besides, benefits of splitting are reduced when blocks are already small.
*/
if (srcSize <= 128 KB || blockSizeMax < 128 KB)
if (srcSize < 128 KB || blockSizeMax < 128 KB)
return MIN(srcSize, blockSizeMax);
/* dynamic splitting has a cpu cost for analysis,
* due to that cost it's only used for btlazy2+ strategies */
* due to that cost it's only used for higher levels */
if (strat >= ZSTD_btopt)
return ZSTD_splitBlock(src, srcSize, blockSizeMax, split_lvl2, cctx->tmpWorkspace, cctx->tmpWkspSize);
if (strat >= ZSTD_lazy2)
return ZSTD_splitBlock(src, srcSize, blockSizeMax, split_lvl1, cctx->tmpWorkspace, cctx->tmpWkspSize);
/* blind split strategy
* no cpu cost, but can over-split homegeneous data.
* heuristic, tested as being "generally better".
* no cpu cost, but can over-split homegeneous data.
* do not split incompressible data though: respect the 3 bytes per block overhead limit.
*/
return savings ? 92 KB : 128 KB;