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Update WAL redo histograms (#2323)

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Previously, it could only distinguish REDO task durations down to 5ms, which
equates to approx. 200pages/sec or 1.6MB/sec getpage@LSN traffic. 
This patch improves to 200'000 pages/sec or 1.6GB/sec, allowing for
much more precise performance measurement of the redo process.
This commit is contained in:
MMeent
2022-08-25 16:17:32 +02:00
committed by GitHub
parent c952f022bb
commit bc588f3a53
1 changed files with 43 additions and 3 deletions
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46
pageserver/src/walredo.rs
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@@ -89,15 +89,52 @@ pub trait WalRedoManager: Send + Sync {
// for access to the postgres process ('wait') since there is only one for
// each tenant.
/// Time buckets are small because we want to be able to measure the
/// smallest redo processing times. These buckets allow us to measure down
/// to 5us, which equates to 200'000 pages/sec, which equates to 1.6GB/sec.
/// This is much better than the previous 5ms aka 200 pages/sec aka 1.6MB/sec.
macro_rules! redo_histogram_time_buckets {
() => {
vec![
0.000_005, 0.000_010, 0.000_025, 0.000_050, 0.000_100, 0.000_250, 0.000_500, 0.001_000,
0.002_500, 0.005_000, 0.010_000, 0.025_000, 0.050_000,
]
};
}
/// While we're at it, also measure the amount of records replayed in each
/// operation. We have a global 'total replayed' counter, but that's not
/// as useful as 'what is the skew for how many records we replay in one
/// operation'.
macro_rules! redo_histogram_count_buckets {
() => {
vec![0.0, 1.0, 2.0, 5.0, 10.0, 25.0, 50.0, 100.0, 250.0, 500.0]
};
}
static WAL_REDO_TIME: Lazy<Histogram> = Lazy::new(|| {
register_histogram!("pageserver_wal_redo_seconds", "Time spent on WAL redo")
.expect("failed to define a metric")
register_histogram!(
"pageserver_wal_redo_seconds",
"Time spent on WAL redo",
redo_histogram_time_buckets!()
)
.expect("failed to define a metric")
});
static WAL_REDO_WAIT_TIME: Lazy<Histogram> = Lazy::new(|| {
register_histogram!(
"pageserver_wal_redo_wait_seconds",
"Time spent waiting for access to the WAL redo process"
"Time spent waiting for access to the WAL redo process",
redo_histogram_time_buckets!(),
)
.expect("failed to define a metric")
});
static WAL_REDO_RECORDS_HISTOGRAM: Lazy<Histogram> = Lazy::new(|| {
register_histogram!(
"pageserver_wal_redo_records_histogram",
"Histogram of number of records replayed per redo",
redo_histogram_count_buckets!(),
)
.expect("failed to define a metric")
});
@@ -262,7 +299,10 @@ impl PostgresRedoManager {
let end_time = Instant::now();
let duration = end_time.duration_since(lock_time);
WAL_REDO_TIME.observe(duration.as_secs_f64());
WAL_REDO_RECORDS_HISTOGRAM.observe(records.len() as f64);
debug!(
"postgres applied {} WAL records in {} us to reconstruct page image at LSN {}",
records.len(),