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Shave some CPU cycles from reading blobs from files.

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This shows up in 'perf' profile when running in debug mode. Not so
significant in release mode, but still.
This commit is contained in:
Heikki Linnakangas
2022-03-14 19:53:00 +02:00
parent 89690d7349
commit 60ed6b3710
2 changed files with 12 additions and 5 deletions
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4
pageserver/src/layered_repository/inmemory_layer.rs
View File

@@ -335,11 +335,13 @@ impl InMemoryLayer {
self.start_lsn..inner.end_lsn.unwrap(),
)?;
let mut buf = Vec::new();
let mut do_steps = || -> Result<()> {
for (key, vec_map) in inner.index.iter() {
// Write all page versions
for (lsn, pos) in vec_map.as_slice() {
let val = Value::des(&utils::read_blob(&inner.file, *pos)?)?;
let len = utils::read_blob_buf(&inner.file, *pos, &mut buf)?;
let val = Value::des(&buf[0..len])?;
delta_layer_writer.put_value(*key, *lsn, val)?;
}
}

13
pageserver/src/layered_repository/utils.rs
View File

@@ -4,17 +4,22 @@ use std::os::unix::fs::FileExt;
use bookfile::BoundedReader;
pub fn read_blob<F: FileExt>(file: &F, off: u64) -> Result<Vec<u8>, Error> {
pub fn read_blob_buf<F: FileExt>(file: &F, off: u64, buf: &mut Vec<u8>) -> Result<usize, Error> {
// read length
let mut len_buf = [0u8; 4];
file.read_exact_at(&mut len_buf, off)?;
let len = u32::from_ne_bytes(len_buf);
let len = u32::from_ne_bytes(len_buf) as usize;
let mut buf: Vec<u8> = Vec::new();
buf.resize(len as usize, 0);
buf.resize(len, 0);
file.read_exact_at(&mut buf.as_mut_slice(), off + 4)?;
Ok(len)
}
pub fn read_blob<F: FileExt>(file: &F, off: u64) -> Result<Vec<u8>, Error> {
let mut buf: Vec<u8> = Vec::new();
let _ = read_blob_buf(file, off, &mut buf);
Ok(buf)
}