[#754] blobstor: Estimate compressability

Now it is possible to enable compressability estimation.
If data is likely uncompressable, it should reduce CPU time and memory.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

config/example/node.env

@@ -113,6 +113,8 @@ FROSTFS_STORAGE_SHARD_0_METABASE_MAX_BATCH_DELAY=10ms
 ### Blobstor config
 FROSTFS_STORAGE_SHARD_0_COMPRESS=true
 FROSTFS_STORAGE_SHARD_0_COMPRESSION_EXCLUDE_CONTENT_TYPES="audio/* video/*"
+FROSTFS_STORAGE_SHARD_0_COMPRESSION_ESTIMATE_COMPRESSIBILITY=true
+FROSTFS_STORAGE_SHARD_0_COMPRESSION_ESTIMATE_COMPRESSIBILITY_THRESHOLD=0.7
 FROSTFS_STORAGE_SHARD_0_SMALL_OBJECT_SIZE=102400
 ### Blobovnicza config
 FROSTFS_STORAGE_SHARD_0_BLOBSTOR_0_PATH=tmp/0/blob/blobovnicza

config/example/node.json

@@ -160,6 +160,8 @@
         "compression_exclude_content_types": [
           "audio/*", "video/*"
         ],
+        "compression_estimate_compressibility": true,
+        "compression_estimate_compressibility_threshold": 0.7,
         "small_object_size": 102400,
         "blobstor": [
           {

config/example/node.yaml

@@ -178,6 +178,8 @@ storage:
       compression_exclude_content_types:
         - audio/*
         - video/*
+      compression_estimate_compressibility: true
+      compression_estimate_compressibility_threshold: 0.7
 
       blobstor:
         - type: blobovnicza