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Reduce number of allocations when compressing and simplify the code.

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Before we were allocating at least once: twice with large table and
thrice when we used a scratch buffer. With this approach we always
allocate once.

  name                                          old speed               new speed               delta
  BM_UFlat/0      [html             ]           2.45GB/s ± 0%           2.45GB/s ± 0%   -0.13%        (p=0.000 n=11+11)
  BM_UFlat/1      [urls             ]           1.19GB/s ± 0%           1.22GB/s ± 0%   +2.48%        (p=0.000 n=11+11)
  BM_UFlat/2      [jpg              ]           17.2GB/s ± 2%           17.3GB/s ± 1%     ~           (p=0.193 n=11+11)
  BM_UFlat/3      [jpg_200          ]           1.52GB/s ± 0%           1.51GB/s ± 0%   -0.78%         (p=0.000 n=10+9)
  BM_UFlat/4      [pdf              ]           12.5GB/s ± 1%           12.5GB/s ± 1%     ~             (p=0.881 n=9+9)
  BM_UFlat/5      [html4            ]           1.86GB/s ± 0%           1.86GB/s ± 0%     ~           (p=0.123 n=11+11)
  BM_UFlat/6      [txt1             ]            793MB/s ± 0%            799MB/s ± 0%   +0.78%         (p=0.000 n=11+9)
  BM_UFlat/7      [txt2             ]            739MB/s ± 0%            744MB/s ± 0%   +0.77%        (p=0.000 n=11+11)
  BM_UFlat/8      [txt3             ]            839MB/s ± 0%            845MB/s ± 0%   +0.71%        (p=0.000 n=11+11)
  BM_UFlat/9      [txt4             ]            678MB/s ± 0%            685MB/s ± 0%   +1.01%        (p=0.000 n=11+11)
  BM_UFlat/10     [pb               ]           3.08GB/s ± 0%           3.12GB/s ± 0%   +1.21%        (p=0.000 n=11+11)
  BM_UFlat/11     [gaviota          ]            975MB/s ± 0%            976MB/s ± 0%   +0.11%        (p=0.000 n=11+11)
  BM_UFlat/12     [cp               ]           1.73GB/s ± 1%           1.74GB/s ± 1%   +0.46%        (p=0.010 n=11+11)
  BM_UFlat/13     [c                ]           1.53GB/s ± 0%           1.53GB/s ± 0%     ~           (p=0.987 n=11+10)
  BM_UFlat/14     [lsp              ]           1.65GB/s ± 0%           1.63GB/s ± 1%   -1.04%        (p=0.000 n=11+11)
  BM_UFlat/15     [xls              ]           1.08GB/s ± 0%           1.15GB/s ± 0%   +6.12%        (p=0.000 n=10+11)
  BM_UFlat/16     [xls_200          ]            944MB/s ± 0%            920MB/s ± 3%   -2.51%         (p=0.000 n=9+11)
  BM_UFlat/17     [bin              ]           1.86GB/s ± 0%           1.87GB/s ± 0%   +0.68%        (p=0.000 n=10+11)
  BM_UFlat/18     [bin_200          ]           1.91GB/s ± 3%           1.92GB/s ± 5%     ~           (p=0.356 n=11+11)
  BM_UFlat/19     [sum              ]           1.31GB/s ± 0%           1.40GB/s ± 0%   +6.53%        (p=0.000 n=11+11)
  BM_UFlat/20     [man              ]           1.42GB/s ± 0%           1.42GB/s ± 0%   +0.33%        (p=0.000 n=10+10)
This commit is contained in:
alkis
2018-10-16 12:28:52 -07:00
committed by Victor Costan
parent df5548c0b3
commit 53a38e5e33
3 changed files with 55 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
snappy-internal.h
View File

@@ -36,19 +36,26 @@
namespace snappy {
namespace internal {
// Working memory performs a single allocation to hold all scratch space
// required for compression.
class WorkingMemory {
public:
WorkingMemory() : large_table_(NULL) { }
~WorkingMemory() { delete[] large_table_; }
explicit WorkingMemory(size_t input_size);
~WorkingMemory();
// Allocates and clears a hash table using memory in "*this",
// stores the number of buckets in "*table_size" and returns a pointer to
// the base of the hash table.
uint16* GetHashTable(size_t input_size, int* table_size);
uint16* GetHashTable(size_t fragment_size, int* table_size) const;
char* GetScratchInput() const { return input_; }
char* GetScratchOutput() const { return output_; }
private:
uint16 small_table_[1<<10]; // 2KB
uint16* large_table_; // Allocated only when needed
char* mem_; // the allocated memory, never nullptr
size_t size_; // the size of the allocated memory, never 0
uint16* table_; // the pointer to the hashtable
char* input_; // the pointer to the input scratch buffer
char* output_; // the pointer to the output scratch buffer
// No copying
WorkingMemory(const WorkingMemory&);