revert memory map for reading snapshot (#25259)

runtime/src/shared_buffer_reader.rs

@@ -24,7 +24,7 @@ use {
 // # bytes allocated and populated by reading ahead
 const TOTAL_BUFFER_BUDGET_DEFAULT: usize = 2_000_000_000;
 // data is read-ahead and saved in chunks of this many bytes
-const CHUNK_SIZE_DEFAULT: usize = 50_000_000;
+const CHUNK_SIZE_DEFAULT: usize = 100_000_000;
 
 type OneSharedBuffer = Arc<Vec<u8>>;
 

runtime/src/snapshot_utils.rs

@@ -22,7 +22,6 @@ use {
     flate2::read::GzDecoder,
     lazy_static::lazy_static,
     log::*,
-    memmap2::Mmap,
     rayon::prelude::*,
     regex::Regex,
     solana_measure::measure::Measure,
@@ -35,7 +34,6 @@ use {
         io::{BufReader, BufWriter, Error as IoError, ErrorKind, Read, Seek, Write},
         path::{Path, PathBuf},
         process::ExitStatus,
-        slice,
         str::FromStr,
         sync::Arc,
     },
@@ -794,8 +792,8 @@ pub struct BankFromArchiveTimings {
     pub verify_snapshot_bank_us: u64,
 }
 
-// From testing, 8 seems to be a sweet spot for ranges of 60M-360M accounts and 16-64 cores. This may need to be tuned later.
-const PARALLEL_UNTAR_READERS_DEFAULT: usize = 8;
+// From testing, 4 seems to be a sweet spot for ranges of 60M-360M accounts and 16-64 cores. This may need to be tuned later.
+const PARALLEL_UNTAR_READERS_DEFAULT: usize = 4;
 
 /// Rebuild bank from snapshot archives.  Handles either just a full snapshot, or both a full
 /// snapshot and an incremental snapshot.
@@ -1523,91 +1521,13 @@ fn untar_snapshot_in<P: AsRef<Path>>(
     archive_format: ArchiveFormat,
     parallel_divisions: usize,
 ) -> Result<UnpackedAppendVecMap> {
-    let ret = untar_snapshot_mmap(
+    untar_snapshot_file(
         snapshot_tar.as_ref(),
         unpack_dir,
         account_paths,
         archive_format,
         parallel_divisions,
-    );
-
-    if ret.is_ok() {
-        ret
-    } else {
-        warn!(
-            "Failed to memory map the snapshot file: {}",
-            snapshot_tar.as_ref().display(),
-        );
-
-        untar_snapshot_file(
-            snapshot_tar.as_ref(),
-            unpack_dir,
-            account_paths,
-            archive_format,
-            parallel_divisions,
-        )
-    }
-}
-
-fn untar_snapshot_mmap(
-    snapshot_tar: &Path,
-    unpack_dir: &Path,
-    account_paths: &[PathBuf],
-    archive_format: ArchiveFormat,
-    parallel_divisions: usize,
-) -> Result<UnpackedAppendVecMap> {
-    let file = File::open(snapshot_tar).unwrap();
-    let mmap = unsafe { Mmap::map(&file) };
-    if mmap.is_err() {
-        return Err(SnapshotError::Io(std::io::Error::new(
-            ErrorKind::Other,
-            "mmap failure",
-        )));
-    }
-
-    let mmap = mmap.unwrap();
-
-    // `unpack_snapshot_local` takes a BufReader creator, which requires a
-    // static lifetime because of its background reader thread. Therefore, we
-    // can't pass the &mmap. Instead, we construct and pass a a slice
-    // explicitly. However, the following code is guaranteed to be safe because
-    // the lifetime of mmap last till the end of the function while the usage of
-    // mmap, BufReader's lifetime only last within fn unpack_snapshot_local.
-    let len = &mmap[..].len();
-    let ptr = &mmap[0] as *const u8;
-    let slice = unsafe { slice::from_raw_parts(ptr, *len) };
-
-    let account_paths_map = match archive_format {
-        ArchiveFormat::TarBzip2 => unpack_snapshot_local(
-            || BzDecoder::new(slice),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::TarGzip => unpack_snapshot_local(
-            || GzDecoder::new(slice),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::TarZstd => unpack_snapshot_local(
-            || zstd::stream::read::Decoder::new(slice).unwrap(),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::TarLz4 => unpack_snapshot_local(
-            || lz4::Decoder::new(slice).unwrap(),
-            unpack_dir,
-            account_paths,
-            parallel_divisions,
-        )?,
-        ArchiveFormat::Tar => {
-            unpack_snapshot_local(|| slice, unpack_dir, account_paths, parallel_divisions)?
-        }
-    };
-
-    Ok(account_paths_map)
+    )
 }
 
 fn verify_unpacked_snapshots_dir_and_version(