Skip to content

Add warning log to EvictionQueue::Purge for slow purges #58

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
krleonid wants to merge 2 commits into
base: v1.5-stable-artjom-ab077c5
Choose a base branch
from
Open

Add warning log to EvictionQueue::Purge for slow purges #58

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
778e566
Add warning log to EvictionQueue::Purge when iterations > 10 or elaps…
krleonid May 25, 2026
4288abb
Derive purge metrics from existing state instead of accumulator params
krleonid May 25, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 25 additions & 3 deletions src/storage/buffer/buffer_pool.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include "duckdb/common/exception.hpp"
#include "duckdb/common/thread.hpp"
#include "duckdb/common/typedefs.hpp"
#include "duckdb/logging/logger.hpp"
#include "duckdb/main/settings.hpp"
#include "duckdb/parallel/concurrentqueue.hpp"
#include "duckdb/parallel/task_scheduler.hpp"
Expand Down Expand Up @@ -96,7 +97,7 @@ struct EvictionQueue {
//! Tries to dequeue an element from the eviction queue, but only after acquiring the purge queue lock.
bool TryDequeueWithLock(BufferEvictionNode &node);
//! Garbage collect dead nodes in the eviction queue.
void Purge();
void Purge(const DatabaseInstance &db);
template <typename FN>
void IterateUnloadableBlocks(FN fn);

Expand Down Expand Up @@ -173,7 +174,7 @@ bool EvictionQueue::TryDequeueWithLock(BufferEvictionNode &node) {
return q.try_dequeue(node);
}

void EvictionQueue::Purge() {
void EvictionQueue::Purge(const DatabaseInstance &db) {
// only one thread purges the queue, all other threads early-out
unique_lock<mutex> guard(purge_lock, std::try_to_lock);
if (!guard.owns_lock()) {
Expand Down Expand Up @@ -208,7 +209,12 @@ void EvictionQueue::Purge() {
// 2.3. We've purged the entire queue: max_purges is zero. This is a worst-case scenario,
// guaranteeing that we always exit the loop.

auto purge_start = std::chrono::steady_clock::now();
idx_t initial_q_size = approx_q_size;
idx_t initial_dead_nodes = total_dead_nodes.load();

idx_t max_purges = approx_q_size / purge_size;
idx_t initial_max_purges = max_purges;

while (max_purges != 0) {
PurgeIteration(purge_size);
Expand All @@ -232,6 +238,22 @@ void EvictionQueue::Purge() {

max_purges--;
}

idx_t iterations = initial_max_purges - max_purges;
idx_t total_dead_found = initial_dead_nodes - total_dead_nodes.load();
idx_t total_alive_found = iterations * purge_size - total_dead_found;
auto elapsed_ms =
std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now() - purge_start).count();
if (iterations > 10 || elapsed_ms > 1000) {
DUCKDB_LOG_WARNING(db,
"EvictionQueue::Purge took %lldms with %llu iterations, "
"queue_size_before=%llu, queue_size_after=%llu, "
"dead_nodes_before=%llu, dead_nodes_after=%llu, "
"total_dequeued=%llu (alive=%llu, dead=%llu)",
elapsed_ms, iterations, initial_q_size, q.size_approx(),
initial_dead_nodes, (idx_t)total_dead_nodes,
total_alive_found + total_dead_found, total_alive_found, total_dead_found);
}
}

void EvictionQueue::PurgeIteration(const idx_t purge_size) {
Expand Down Expand Up @@ -524,7 +546,7 @@ void BufferPool::PurgeQueue(const BlockHandle &block) {
const auto queue_sleep_micros =
Settings::Get<DebugEvictionQueueSleepMicroSecondsSetting>(buffer_manager.GetDatabase());
eviction_queue.debug_eviction_queue_sleep = queue_sleep_micros;
eviction_queue.Purge();
eviction_queue.Purge(buffer_manager.GetDatabase());
}

void BufferPool::SetLimit(idx_t limit, const char *exception_postscript) {
Expand Down
Loading