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WIP: page_cache Prometheus metrics

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This commit is contained in:
Christian Schwarz
2023-06-30 21:01:59 +02:00
parent 73acc17bf8
commit 6a8cd9757b
2 changed files with 59 additions and 2 deletions
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18
pageserver/src/metrics.rs
View File

@@ -130,6 +130,24 @@ pub static MATERIALIZED_PAGE_CACHE_HIT: Lazy<IntCounter> = Lazy::new(|| {
.expect("failed to define a metric")
});
pub static PAGE_CACHE_READ_ACCESSES: Lazy<IntCounterVec> = Lazy::new(|| {
register_int_counter_vec!(
"pageserver_page_cache_read_accesses_total",
"Number of read accesses to the page cache",
&["key_kind"]
)
.expect("failed to define a metric")
});
pub static PAGE_CACHE_READ_HITS: Lazy<IntCounterVec> = Lazy::new(|| {
register_int_counter_vec!(
"pageserver_page_cache_read_hits_total",
"Number of read accesses to the page cache that hit",
&["key_kind", "hit_kind"]
)
.expect("failed to define a metric")
});
static WAIT_LSN_TIME: Lazy<HistogramVec> = Lazy::new(|| {
register_histogram_vec!(
"pageserver_wait_lsn_seconds",

43
pageserver/src/page_cache.rs
View File

@@ -313,6 +313,11 @@ impl PageCache {
key: &Key,
lsn: Lsn,
) -> Option<(Lsn, PageReadGuard)> {
crate::metrics::PAGE_CACHE_READ_ACCESSES
.get_metric_with_label_values(&["materialized_page"])
.unwrap()
.inc();
let mut cache_key = CacheKey::MaterializedPage {
hash_key: MaterializedPageHashKey {
tenant_id,
@@ -323,8 +328,23 @@ impl PageCache {
};
if let Some(guard) = self.try_lock_for_read(&mut cache_key) {
if let CacheKey::MaterializedPage { hash_key: _, lsn } = cache_key {
Some((lsn, guard))
if let CacheKey::MaterializedPage {
hash_key: _,
lsn: available_lsn,
} = cache_key
{
if available_lsn == lsn {
crate::metrics::PAGE_CACHE_READ_HITS
.get_metric_with_label_values(&["materialized_page", "exact"])
.unwrap()
.inc();
} else {
crate::metrics::PAGE_CACHE_READ_HITS
.get_metric_with_label_values(&["materialized_page", "older_lsn"])
.unwrap()
.inc();
}
Some((available_lsn, guard))
} else {
panic!("unexpected key type in slot");
}
@@ -499,11 +519,30 @@ impl PageCache {
/// ```
///
fn lock_for_read(&self, cache_key: &mut CacheKey) -> anyhow::Result<ReadBufResult> {
let key_kind = match cache_key {
CacheKey::MaterializedPage { .. } => {
unreachable!("Materialized pages use lookup_materialized_page")
}
CacheKey::EphemeralPage { .. } => "ephemeral",
CacheKey::ImmutableFilePage { .. } => "immutable",
};
crate::metrics::PAGE_CACHE_READ_ACCESSES
.get_metric_with_label_values(&[key_kind])
.unwrap()
.inc();
let mut is_first_iteration = true;
loop {
// First check if the key already exists in the cache.
if let Some(read_guard) = self.try_lock_for_read(cache_key) {
if is_first_iteration {
crate::metrics::PAGE_CACHE_READ_HITS
.get_metric_with_label_values(&[key_kind, "-"])
.unwrap()
.inc();
}
return Ok(ReadBufResult::Found(read_guard));
}
is_first_iteration = false;
// Not found. Find a victim buffer
let (slot_idx, mut inner) =