Thang Pham ed102f44d9 Reduce memory allocations for page server (#2010) ...

## Overview

This patch reduces the number of memory allocations when running the page server under a heavy write workload. This mostly helps improve the speed of WAL record ingestion. 

## Changes
- modified `DatadirModification` to allow reuse the struct's allocated memory after each modification
- modified `decode_wal_record` to allow passing a `DecodedWALRecord` reference. This helps reuse the struct in each `decode_wal_record` call
- added a reusable buffer for serializing object inside the `InMemoryLayer::put_value` function
- added a performance test simulating a heavy write workload for testing the changes in this patch

### Semi-related changes
- remove redundant serializations when calling `DeltaLayer::put_value` during `InMemoryLayer::write_to_disk` function call [1]
- removed the info span `info_span!("processing record", lsn = %lsn)` during each WAL ingestion [2]

## Notes
- [1]: in `InMemoryLayer::write_to_disk`, a deserialization is called
  ```
  let val = Value::des(&buf)?;
  delta_layer_writer.put_value(key, *lsn, val)?;
  ``` 
  `DeltaLayer::put_value` then creates a serialization based on the previous deserialization
  ```
  let off = self.blob_writer.write_blob(&Value::ser(&val)?)?;
  ```
- [2]: related: https://github.com/neondatabase/neon/issues/733

2022-07-21 12:08:26 -04:00

..

src

Reduce memory allocations for page server (#2010)

2022-07-21 12:08:26 -04:00

Cargo.toml

Clean up unnecessary dependencies.

2022-07-20 16:31:25 +03:00