import: increase default region-split-size to 512 MiB (tikv#4347)

This makes the SST size to upload larger, which reduces the number of SST
files needed to ingested, and improve overall speed.

Signed-off-by: kennytm <kennytm@gmail.com>

etc/tikv-importer.toml

@@ -46,7 +46,7 @@ num-import-jobs = 24
 # maximum duration to prepare regions.
 # max-prepare-duration = "5m"
 # split regions into this size according to the importing data.
-# region-split-size = "96MB"
+# region-split-size = "512MB"
 # stream channel window size, stream will be blocked on channel full.
 # stream-channel-window = 128
 # maximum number of open engines

src/import/config.rs

@@ -14,7 +14,6 @@
 use std::error::Error;
 use std::result::Result;
 
-use crate::raftstore::coprocessor::config::SPLIT_SIZE_MB;
 use crate::util::config::{ReadableDuration, ReadableSize};
 
 #[derive(Clone, Serialize, Deserialize, PartialEq, Debug)]
@@ -39,7 +38,7 @@ impl Default for Config {
             num_import_jobs: 8,
             num_import_sst_jobs: 2,
             max_prepare_duration: ReadableDuration::minutes(5),
-            region_split_size: ReadableSize::mb(SPLIT_SIZE_MB),
+            region_split_size: ReadableSize::mb(512),
             stream_channel_window: 128,
             max_open_engines: 8,
         }