erasure-code: Add parity delta write optimization to SHEC

This commit adds FLAG_EC_PLUGIN_PARITY_DELTA_OPTIMIZATION to the list of
optimizations supported by the SHEC plugin, and encode_delta and
apply_delta functions.

Signed-off-by: Jamie Pryde <[email protected]>
Signed-off-by: Alex Ainscow <[email protected]>

Author: jamiepryde

src/erasure-code/shec/ErasureCodeShec.cc

@@ -273,6 +273,48 @@ int ErasureCodeShecReedSolomonVandermonde::shec_decode(int *erased,
   return shec_matrix_decode(erased, avails, data, coding, blocksize);
 }
 
+void ErasureCodeShecReedSolomonVandermonde::encode_delta(const bufferptr &old_data,
+                                                         const bufferptr &new_data,
+                                                         bufferptr *delta_maybe_in_place)
+{
+  if (&old_data != delta_maybe_in_place) {
+    memcpy(delta_maybe_in_place->c_str(), old_data.c_str(), delta_maybe_in_place->length());
+  }
+  char *new_data_p = const_cast<char*>(new_data.c_str());
+  char *delta_p = delta_maybe_in_place->c_str();
+  galois_region_xor(new_data_p, delta_p, delta_maybe_in_place->length());
+}
+
+void ErasureCodeShecReedSolomonVandermonde::apply_delta(const shard_id_map<bufferptr> &in,
+                                                        shard_id_map<bufferptr> &out)
+{
+  auto first = in.begin();
+  const unsigned blocksize = first->second.length();
+
+  for (auto const& [datashard, databuf] : in) {
+    if (datashard < k) {
+      for (auto const& [codingshard, codingbuf] : out) {
+        if (codingshard >= k) {
+          ceph_assert(codingbuf.length() == blocksize);
+          char* input_data = const_cast<char*>(databuf.c_str());
+          char* output_data = const_cast<char*>(codingbuf.c_str());
+          switch (w) {
+            case 8:
+              galois_w08_region_multiply(input_data, matrix[static_cast<int>(datashard) + (k * (static_cast<int>(codingshard) - k))], blocksize, output_data, 1);
+              break;
+            case 16:
+              galois_w16_region_multiply(input_data, matrix[static_cast<int>(datashard) + (k * (static_cast<int>(codingshard) - k))], blocksize, output_data, 1);
+              break;
+            case 32:
+              galois_w32_region_multiply(input_data, matrix[datashard + (k * (codingshard - k))], blocksize, output_data, 1);
+              break;
+          }
+        }
+      }
+    }
+  }
+}
+
 unsigned ErasureCodeShecReedSolomonVandermonde::get_alignment() const
 {
   return k*w*sizeof(int);

src/erasure-code/shec/ErasureCodeShec.h

@@ -64,7 +64,8 @@ class ErasureCodeShec : public ceph::ErasureCode {
   uint64_t get_supported_optimizations() const override {
     return FLAG_EC_PLUGIN_PARTIAL_READ_OPTIMIZATION |
       FLAG_EC_PLUGIN_PARTIAL_WRITE_OPTIMIZATION |
-      FLAG_EC_PLUGIN_ZERO_INPUT_ZERO_OUTPUT_OPTIMIZATION;
+      FLAG_EC_PLUGIN_ZERO_INPUT_ZERO_OUTPUT_OPTIMIZATION |
+      FLAG_EC_PLUGIN_PARITY_DELTA_OPTIMIZATION;
   }
 
   unsigned int get_chunk_count() const override {
@@ -144,6 +145,13 @@ class ErasureCodeShecReedSolomonVandermonde final : public ErasureCodeShec {
 			  char **data,
 			  char **coding,
 			  int blocksize) override;
+
+  void encode_delta(const ceph::bufferptr &old_data,
+                    const ceph::bufferptr &new_data,
+                    ceph::bufferptr *delta_maybe_in_place);
+	void apply_delta(const shard_id_map<ceph::bufferptr> &in,
+	                 shard_id_map<ceph::bufferptr> &out);
+
   unsigned get_alignment() const override;
   size_t get_minimum_granularity() override
   {