Add performance test for prefetch in LFC

test_runner/performance/test_lfc_prefetch.py

@@ -0,0 +1,91 @@
+from __future__ import annotations
+
+import random
+import threading
+import time
+
+import pytest
+from fixtures.log_helper import log
+from fixtures.neon_fixtures import NeonEnv
+from fixtures.utils import USE_LFC
+
+
+@pytest.mark.timeout(1000)
+@pytest.mark.skipif(not USE_LFC, reason="LFC is disabled, skipping")
+def test_lfc_prefetch(neon_simple_env: NeonEnv):
+    """
+    Test resizing the Local File Cache
+    """
+    env = neon_simple_env
+    endpoint = env.endpoints.create_start(
+        "main",
+        config_lines=[
+            "neon.max_file_cache_size=10MB",
+            "neon.file_cache_size_limit=10MB",
+            "effective_io_concurrency=100",
+            "shared_buffers=1MB",
+            "enable_bitmapscan=off",
+            "enable_seqscan=off",
+            "autovacuum=off",
+            "statement_timeout=0",
+            "neon.store_prefetch_result_in_lfc=on",
+        ],
+    )
+    n_records = 10000  # 80Mb table
+    top_n = n_records // 4  # 20Mb - should be larger than LFC size
+    test_time = 100.0  # seconds
+    n_readers = 10
+    n_writers = 2
+
+    conn = endpoint.connect()
+    cur = conn.cursor()
+    cur.execute(
+        "create table account(id integer primary key, balance integer default 0, filler text default repeat('?',1000)) with (fillfactor=10)"
+    )
+    cur.execute(f"insert into account values (generate_series(1,{n_records}))")
+    cur.execute("vacuum account")
+
+    def reader():
+        conn = endpoint.connect()
+        cur = conn.cursor()
+        i = 0
+        while running:
+            cur.execute(
+                f"select sum(balance) from (select balance from account order by id limit {top_n}) s"
+            )
+            sum = cur.fetchall()[0][0]
+            assert sum == 0  # check consistency
+            i += 1
+        log.info(f"Did {i} index scans")
+
+    def writer():
+        conn = endpoint.connect()
+        cur = conn.cursor()
+        i = 0
+        while running:
+            r1 = random.randint(1, top_n)
+            r2 = random.randint(1, top_n)
+            # avoid deadlock by ordering src and dst
+            src = min(r1, r2)
+            dst = max(r1, r2)
+            cur.execute(
+                f"update account set balance=balance-1 where id={src}; update account set balance=balance+1 where id={dst}"
+            )
+            i += 1
+        log.info(f"Did {i} updates")
+
+    readers = [threading.Thread(target=reader) for _ in range(n_readers)]
+    writers = [threading.Thread(target=writer) for _ in range(n_writers)]
+
+    running = True
+    for t in readers:
+        t.start()
+    for t in writers:
+        t.start()
+
+    time.sleep(test_time)
+    running = False
+    for t in readers:
+        t.join()
+    for t in writers:
+        t.join()