Add views for metrics about pageserver requests (#9008)

The metrics include a histogram of how long we need to wait for a
GetPage request, number of reconnects, and number of requests among
other things.

The metrics are not yet exported anywhere, but you can query them
manually.

Note: This does *not* bump the default version of the 'neon' extension. We
will do that later, as a separate PR. The reason is that this allows us to roll back
the compute image smoothly, if necessary. Once the image that includes the
new extension .so file with the new functions has been rolled out, and we're
confident that we don't need to roll back the image anymore, we can change
default extension version and actually start using the new functions and views.

This is what the view looks like:

```
postgres=# select * from neon_perf_counters ;
                metric                 | bucket_le |  value   
---------------------------------------+-----------+----------
 getpage_wait_seconds_count            |           |      300
 getpage_wait_seconds_sum              |           | 0.048506
 getpage_wait_seconds_bucket           |     2e-05 |        0
 getpage_wait_seconds_bucket           |     3e-05 |        0
 getpage_wait_seconds_bucket           |     6e-05 |       71
 getpage_wait_seconds_bucket           |    0.0001 |      124
 getpage_wait_seconds_bucket           |    0.0002 |      248
 getpage_wait_seconds_bucket           |    0.0003 |      279
 getpage_wait_seconds_bucket           |    0.0006 |      297
 getpage_wait_seconds_bucket           |     0.001 |      298
 getpage_wait_seconds_bucket           |     0.002 |      298
 getpage_wait_seconds_bucket           |     0.003 |      298
 getpage_wait_seconds_bucket           |     0.006 |      300
 getpage_wait_seconds_bucket           |      0.01 |      300
 getpage_wait_seconds_bucket           |      0.02 |      300
 getpage_wait_seconds_bucket           |      0.03 |      300
 getpage_wait_seconds_bucket           |      0.06 |      300
 getpage_wait_seconds_bucket           |       0.1 |      300
 getpage_wait_seconds_bucket           |       0.2 |      300
 getpage_wait_seconds_bucket           |       0.3 |      300
 getpage_wait_seconds_bucket           |       0.6 |      300
 getpage_wait_seconds_bucket           |         1 |      300
 getpage_wait_seconds_bucket           |         2 |      300
 getpage_wait_seconds_bucket           |         3 |      300
 getpage_wait_seconds_bucket           |         6 |      300
 getpage_wait_seconds_bucket           |        10 |      300
 getpage_wait_seconds_bucket           |        20 |      300
 getpage_wait_seconds_bucket           |        30 |      300
 getpage_wait_seconds_bucket           |        60 |      300
 getpage_wait_seconds_bucket           |       100 |      300
 getpage_wait_seconds_bucket           |  Infinity |      300
 getpage_prefetch_requests_total       |           |       69
 getpage_sync_requests_total           |           |      231
 getpage_prefetch_misses_total         |           |        0
 getpage_prefetch_discards_total       |           |        0
 pageserver_requests_sent_total        |           |      323
 pageserver_requests_disconnects_total |           |        0
 pageserver_send_flushes_total         |           |      323
 file_cache_hits_total                 |           |        0
(39 rows)
```

pgxn/neon/Makefile

@@ -9,6 +9,8 @@ OBJS = \
 	hll.o \
 	libpagestore.o \
 	neon.o \
+	neon_pgversioncompat.o \
+	neon_perf_counters.o \
 	neon_utils.o \
 	neon_walreader.o \
 	pagestore_smgr.o \
@@ -23,7 +25,7 @@ SHLIB_LINK_INTERNAL = $(libpq)
 SHLIB_LINK = -lcurl
 
 EXTENSION = neon
-DATA = neon--1.0.sql neon--1.0--1.1.sql neon--1.1--1.2.sql neon--1.2--1.3.sql neon--1.3--1.2.sql neon--1.2--1.1.sql neon--1.1--1.0.sql  neon--1.3--1.4.sql neon--1.4--1.3.sql
+DATA = neon--1.0.sql neon--1.0--1.1.sql neon--1.1--1.2.sql neon--1.2--1.3.sql neon--1.3--1.2.sql neon--1.2--1.1.sql neon--1.1--1.0.sql  neon--1.3--1.4.sql neon--1.4--1.3.sql neon--1.4--1.5.sql neon--1.5--1.4.sql
 PGFILEDESC = "neon - cloud storage for PostgreSQL"
 
 EXTRA_CLEAN = \

pgxn/neon/libpagestore.c

@@ -30,6 +30,7 @@
 #include "utils/guc.h"
 
 #include "neon.h"
+#include "neon_perf_counters.h"
 #include "neon_utils.h"
 #include "pagestore_client.h"
 #include "walproposer.h"
@@ -331,6 +332,7 @@ CLEANUP_AND_DISCONNECT(PageServer *shard)
 	}
 	if (shard->conn)
 	{
+		MyNeonCounters->pageserver_disconnects_total++;
 		PQfinish(shard->conn);
 		shard->conn = NULL;
 	}
@@ -737,6 +739,8 @@ pageserver_send(shardno_t shard_no, NeonRequest *request)
 	PageServer *shard = &page_servers[shard_no];
 	PGconn	   *pageserver_conn;
 
+	MyNeonCounters->pageserver_requests_sent_total++;
+
 	/* If the connection was lost for some reason, reconnect */
 	if (shard->state == PS_Connected && PQstatus(shard->conn) == CONNECTION_BAD)
 	{
@@ -889,6 +893,7 @@ pageserver_flush(shardno_t shard_no)
 	}
 	else
 	{
+		MyNeonCounters->pageserver_send_flushes_total++;
 		if (PQflush(pageserver_conn))
 		{
 			char	   *msg = pchomp(PQerrorMessage(pageserver_conn));
@@ -922,7 +927,7 @@ check_neon_id(char **newval, void **extra, GucSource source)
 static Size
 PagestoreShmemSize(void)
 {
-	return sizeof(PagestoreShmemState);
+	return add_size(sizeof(PagestoreShmemState), NeonPerfCountersShmemSize());
 }
 
 static bool
@@ -941,6 +946,9 @@ PagestoreShmemInit(void)
 		memset(&pagestore_shared->shard_map, 0, sizeof(ShardMap));
 		AssignPageserverConnstring(page_server_connstring, NULL);
 	}
+
+	NeonPerfCountersShmemInit();
+
 	LWLockRelease(AddinShmemInitLock);
 	return found;
 }

pgxn/neon/neon--1.4--1.5.sql

@@ -0,0 +1,39 @@
+\echo Use "ALTER EXTENSION neon UPDATE TO '1.5'" to load this file. \quit
+
+
+CREATE FUNCTION get_backend_perf_counters()
+RETURNS SETOF RECORD
+AS 'MODULE_PATHNAME', 'neon_get_backend_perf_counters'
+LANGUAGE C PARALLEL SAFE;
+
+CREATE FUNCTION get_perf_counters()
+RETURNS SETOF RECORD
+AS 'MODULE_PATHNAME', 'neon_get_perf_counters'
+LANGUAGE C PARALLEL SAFE;
+
+-- Show various metrics, for each backend. Note that the values are not reset
+-- when a backend exits. When a new backend starts with the backend ID, it will
+-- continue accumulating the values from where the old backend left. If you are
+-- only interested in the changes from your own session, store the values at the
+-- beginning of the session somewhere, and subtract them on subsequent calls.
+--
+-- For histograms, 'bucket_le' is the upper bound of the histogram bucket.
+CREATE VIEW neon_backend_perf_counters AS
+  SELECT P.procno, P.pid, P.metric, P.bucket_le, P.value
+  FROM get_backend_perf_counters() AS P (
+    procno integer,
+    pid integer,
+    metric text,
+    bucket_le float8,
+    value float8
+  );
+
+-- Summary across all backends. (This could also be implemented with
+-- an aggregate query over neon_backend_perf_counters view.)
+CREATE VIEW neon_perf_counters AS
+  SELECT P.metric, P.bucket_le, P.value
+  FROM get_perf_counters() AS P (
+    metric text,
+    bucket_le float8,
+    value float8
+  );

pgxn/neon/neon--1.5--1.4.sql

@@ -0,0 +1,4 @@
+DROP VIEW IF EXISTS neon_perf_counters;
+DROP VIEW IF EXISTS neon_backend_perf_counters;
+DROP FUNCTION IF EXISTS get_perf_counters();
+DROP FUNCTION IF EXISTS get_backend_perf_counters();

pgxn/neon/neon.control

@@ -1,5 +1,7 @@
 # neon extension
 comment = 'cloud storage for PostgreSQL'
+# TODO: bump default version to 1.5, after we are certain that we don't
+# need to rollback the compute image
 default_version = '1.4'
 module_pathname = '$libdir/neon'
 relocatable = true

pgxn/neon/neon_perf_counters.c

@@ -0,0 +1,261 @@
+/*-------------------------------------------------------------------------
+ *
+ * neon_perf_counters.c
+ *	  Collect statistics about Neon I/O
+ *
+ * Each backend has its own set of counters in shared memory.
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <math.h>
+
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "storage/proc.h"
+#include "storage/shmem.h"
+#include "utils/builtins.h"
+
+#include "neon_perf_counters.h"
+#include "neon_pgversioncompat.h"
+
+neon_per_backend_counters *neon_per_backend_counters_shared;
+
+Size
+NeonPerfCountersShmemSize(void)
+{
+	Size		size = 0;
+
+	size = add_size(size, mul_size(MaxBackends, sizeof(neon_per_backend_counters)));
+
+	return size;
+}
+
+bool
+NeonPerfCountersShmemInit(void)
+{
+	bool		found;
+
+	neon_per_backend_counters_shared =
+		ShmemInitStruct("Neon perf counters",
+						mul_size(MaxBackends,
+								 sizeof(neon_per_backend_counters)),
+						&found);
+	Assert(found == IsUnderPostmaster);
+	if (!found)
+	{
+		/* shared memory is initialized to zeros, so nothing to do here */
+	}
+}
+
+/*
+ * Count a GetPage wait operation.
+ */
+void
+inc_getpage_wait(uint64 latency_us)
+{
+	int			lo = 0;
+	int			hi = NUM_GETPAGE_WAIT_BUCKETS - 1;
+
+	/* Find the right bucket with binary search */
+	while (lo < hi)
+	{
+		int			mid = (lo + hi) / 2;
+
+		if (latency_us < getpage_wait_bucket_thresholds[mid])
+			hi = mid;
+		else
+			lo = mid + 1;
+	}
+	MyNeonCounters->getpage_wait_us_bucket[lo]++;
+	MyNeonCounters->getpage_wait_us_sum += latency_us;
+	MyNeonCounters->getpage_wait_us_count++;
+}
+
+/*
+ * Support functions for the views, neon_backend_perf_counters and
+ * neon_perf_counters.
+ */
+
+typedef struct
+{
+	char	   *name;
+	bool		is_bucket;
+	double		bucket_le;
+	double		value;
+} metric_t;
+
+static metric_t *
+neon_perf_counters_to_metrics(neon_per_backend_counters *counters)
+{
+#define NUM_METRICS (2 + NUM_GETPAGE_WAIT_BUCKETS + 8)
+	metric_t   *metrics = palloc((NUM_METRICS + 1) * sizeof(metric_t));
+	uint64		bucket_accum;
+	int			i = 0;
+	Datum		getpage_wait_str;
+
+	metrics[i].name = "getpage_wait_seconds_count";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->getpage_wait_us_count;
+	i++;
+	metrics[i].name = "getpage_wait_seconds_sum";
+	metrics[i].is_bucket = false;
+	metrics[i].value = ((double) counters->getpage_wait_us_sum) / 1000000.0;
+	i++;
+
+	bucket_accum = 0;
+	for (int bucketno = 0; bucketno < NUM_GETPAGE_WAIT_BUCKETS; bucketno++)
+	{
+		uint64		threshold = getpage_wait_bucket_thresholds[bucketno];
+
+		bucket_accum += counters->getpage_wait_us_bucket[bucketno];
+
+		metrics[i].name = "getpage_wait_seconds_bucket";
+		metrics[i].is_bucket = true;
+		metrics[i].bucket_le = (threshold == UINT64_MAX) ? INFINITY : ((double) threshold) / 1000000.0;
+		metrics[i].value = (double) bucket_accum;
+		i++;
+	}
+	metrics[i].name = "getpage_prefetch_requests_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->getpage_prefetch_requests_total;
+	i++;
+	metrics[i].name = "getpage_sync_requests_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->getpage_sync_requests_total;
+	i++;
+	metrics[i].name = "getpage_prefetch_misses_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->getpage_prefetch_misses_total;
+	i++;
+	metrics[i].name = "getpage_prefetch_discards_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->getpage_prefetch_discards_total;
+	i++;
+	metrics[i].name = "pageserver_requests_sent_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->pageserver_requests_sent_total;
+	i++;
+	metrics[i].name = "pageserver_requests_disconnects_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->pageserver_disconnects_total;
+	i++;
+	metrics[i].name = "pageserver_send_flushes_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->pageserver_send_flushes_total;
+	i++;
+	metrics[i].name = "file_cache_hits_total";
+	metrics[i].is_bucket = false;
+	metrics[i].value = (double) counters->file_cache_hits_total;
+	i++;
+
+	Assert(i == NUM_METRICS);
+
+	/* NULL entry marks end of array */
+	metrics[i].name = NULL;
+	metrics[i].value = 0;
+
+	return metrics;
+}
+
+/*
+ * Write metric to three output Datums
+ */
+static void
+metric_to_datums(metric_t *m, Datum *values, bool *nulls)
+{
+	values[0] = CStringGetTextDatum(m->name);
+	nulls[0] = false;
+	if (m->is_bucket)
+	{
+		values[1] = Float8GetDatum(m->bucket_le);
+		nulls[1] = false;
+	}
+	else
+	{
+		values[1] = (Datum) 0;
+		nulls[1] = true;
+	}
+	values[2] = Float8GetDatum(m->value);
+	nulls[2] = false;
+}
+
+PG_FUNCTION_INFO_V1(neon_get_backend_perf_counters);
+Datum
+neon_get_backend_perf_counters(PG_FUNCTION_ARGS)
+{
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	Datum		values[5];
+	bool		nulls[5];
+
+	/* We put all the tuples into a tuplestore in one go. */
+	InitMaterializedSRF(fcinfo, 0);
+
+	for (int procno = 0; procno < MaxBackends; procno++)
+	{
+		PGPROC	   *proc = GetPGProcByNumber(procno);
+		int			pid = proc->pid;
+		neon_per_backend_counters *counters = &neon_per_backend_counters_shared[procno];
+		metric_t   *metrics = neon_perf_counters_to_metrics(counters);
+
+		values[0] = Int32GetDatum(procno);
+		nulls[0] = false;
+		values[1] = Int32GetDatum(pid);
+		nulls[1] = false;
+
+		for (int i = 0; metrics[i].name != NULL; i++)
+		{
+			metric_to_datums(&metrics[i], &values[2], &nulls[2]);
+			tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+		}
+
+		pfree(metrics);
+	}
+
+	return (Datum) 0;
+}
+
+PG_FUNCTION_INFO_V1(neon_get_perf_counters);
+Datum
+neon_get_perf_counters(PG_FUNCTION_ARGS)
+{
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	Datum		values[3];
+	bool		nulls[3];
+	Datum		getpage_wait_str;
+	neon_per_backend_counters totals = {0};
+	metric_t   *metrics;
+
+	/* We put all the tuples into a tuplestore in one go. */
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* Aggregate the counters across all backends */
+	for (int procno = 0; procno < MaxBackends; procno++)
+	{
+		neon_per_backend_counters *counters = &neon_per_backend_counters_shared[procno];
+
+		totals.getpage_wait_us_count += counters->getpage_wait_us_count;
+		totals.getpage_wait_us_sum += counters->getpage_wait_us_sum;
+		for (int bucketno = 0; bucketno < NUM_GETPAGE_WAIT_BUCKETS; bucketno++)
+			totals.getpage_wait_us_bucket[bucketno] += counters->getpage_wait_us_bucket[bucketno];
+		totals.getpage_prefetch_requests_total += counters->getpage_prefetch_requests_total;
+		totals.getpage_sync_requests_total += counters->getpage_sync_requests_total;
+		totals.getpage_prefetch_misses_total += counters->getpage_prefetch_misses_total;
+		totals.getpage_prefetch_discards_total += counters->getpage_prefetch_discards_total;
+		totals.pageserver_requests_sent_total += counters->pageserver_requests_sent_total;
+		totals.pageserver_disconnects_total += counters->pageserver_disconnects_total;
+		totals.pageserver_send_flushes_total += counters->pageserver_send_flushes_total;
+		totals.file_cache_hits_total += counters->file_cache_hits_total;
+	}
+
+	metrics = neon_perf_counters_to_metrics(&totals);
+	for (int i = 0; metrics[i].name != NULL; i++)
+	{
+		metric_to_datums(&metrics[i], &values[0], &nulls[0]);
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+	}
+	pfree(metrics);
+
+	return (Datum) 0;
+}

pgxn/neon/neon_perf_counters.h

@@ -0,0 +1,111 @@
+/*-------------------------------------------------------------------------
+ *
+ * neon_perf_counters.h
+ *	  Performance counters for neon storage requests
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef NEON_PERF_COUNTERS_H
+#define NEON_PERF_COUNTERS_H
+
+#if PG_VERSION_NUM >= 170000
+#include "storage/procnumber.h"
+#else
+#include "storage/backendid.h"
+#include "storage/proc.h"
+#endif
+
+static const uint64 getpage_wait_bucket_thresholds[] = {
+	      20,       30,       60,       100,  /* 0      -  100 us */
+	     200,      300,      600,	   1000,  /* 100 us - 1 ms */
+	    2000,     3000,     6000,     10000,  /* 1 ms   - 10 ms */
+	   20000,    30000,    60000,    100000,  /* 10 ms  - 100 ms */
+	  200000,   300000,   600000,   1000000,  /* 100 ms - 1 s */
+	 2000000,  3000000,  6000000,  10000000,  /* 1 s - 10 s */
+    20000000, 30000000, 60000000, 100000000,  /* 10 s - 100 s */
+	UINT64_MAX,
+};
+#define NUM_GETPAGE_WAIT_BUCKETS (lengthof(getpage_wait_bucket_thresholds))
+
+typedef struct
+{
+	/*
+	 * Histogram for how long an smgrread() request needs to wait for response
+	 * from pageserver. When prefetching is effective, these wait times can be
+	 * lower than the network latency to the pageserver, even zero, if the
+	 * page is already readily prefetched whenever we need to read a page.
+	 *
+	 * Note: we accumulate these in microseconds, because that's convenient in
+	 * the backend, but the 'neon_backend_perf_counters' view will convert
+	 * them to seconds, to make them more idiomatic as prometheus metrics.
+	 */
+	uint64		getpage_wait_us_count;
+	uint64		getpage_wait_us_sum;
+	uint64		getpage_wait_us_bucket[NUM_GETPAGE_WAIT_BUCKETS];
+
+	/*
+	 * Total number of speculative prefetch Getpage requests and synchronous
+	 * GetPage requests sent.
+	 */
+	uint64		getpage_prefetch_requests_total;
+	uint64		getpage_sync_requests_total;
+
+	/* XXX: It's not clear to me when these misses happen. */
+	uint64		getpage_prefetch_misses_total;
+
+	/*
+	 * Number of prefetched responses that were discarded becuase the
+	 * prefetched page was not needed or because it was concurrently fetched /
+	 * modified by another backend.
+	 */
+	uint64		getpage_prefetch_discards_total;
+
+	/*
+	 * Total number of requests send to pageserver. (prefetch_requests_total
+	 * and sync_request_total count only GetPage requests, this counts all
+	 * request types.)
+	 */
+	uint64		pageserver_requests_sent_total;
+
+	/*
+	 * Number of times the connection to the pageserver was lost and the
+	 * backend had to reconnect. Note that this doesn't count the first
+	 * connection in each backend, only reconnects.
+	 */
+	uint64		pageserver_disconnects_total;
+
+	/*
+	 * Number of network flushes to the pageserver. Synchronous requests are
+	 * flushed immediately, but when prefetching requests are sent in batches,
+	 * this can be smaller than pageserver_requests_sent_total.
+	 */
+	uint64		pageserver_send_flushes_total;
+
+	/*
+	 * Number of requests satisfied from the LFC.
+	 *
+	 * This is redundant with the server-wide file_cache_hits, but this gives
+	 * per-backend granularity, and it's handy to have this in the same place
+	 * as counters for requests that went to the pageserver. Maybe move all
+	 * the LFC stats to this struct in the future?
+	 */
+	uint64		file_cache_hits_total;
+
+} neon_per_backend_counters;
+
+/* Pointer to the shared memory array of neon_per_backend_counters structs */
+extern neon_per_backend_counters *neon_per_backend_counters_shared;
+
+#if PG_VERSION_NUM >= 170000
+#define MyNeonCounters (&neon_per_backend_counters_shared[MyProcNumber])
+#else
+#define MyNeonCounters (&neon_per_backend_counters_shared[MyProc->pgprocno])
+#endif
+
+extern void inc_getpage_wait(uint64 latency);
+
+extern Size NeonPerfCountersShmemSize(void);
+extern bool NeonPerfCountersShmemInit(void);
+
+
+#endif							/* NEON_PERF_COUNTERS_H */

pgxn/neon/neon_pgversioncompat.c

@@ -0,0 +1,44 @@
+/*
+ * Support functions for the compatibility macros in neon_pgversioncompat.h
+ */
+#include "postgres.h"
+
+#include "funcapi.h"
+#include "miscadmin.h"
+#include "utils/tuplestore.h"
+
+#include "neon_pgversioncompat.h"
+
+#if PG_MAJORVERSION_NUM < 15
+void
+InitMaterializedSRF(FunctionCallInfo fcinfo, bits32 flags)
+{
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	Tuplestorestate *tupstore;
+	MemoryContext old_context,
+				per_query_ctx;
+	TupleDesc	stored_tupdesc;
+
+	/* check to see if caller supports returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+
+	/*
+	 * Store the tuplestore and the tuple descriptor in ReturnSetInfo.  This
+	 * must be done in the per-query memory context.
+	 */
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	old_context = MemoryContextSwitchTo(per_query_ctx);
+
+	if (get_call_result_type(fcinfo, NULL, &stored_tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	tupstore = tuplestore_begin_heap(false, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = stored_tupdesc;
+	MemoryContextSwitchTo(old_context);
+}
+#endif

pgxn/neon/neon_pgversioncompat.h

@@ -6,6 +6,8 @@
 #ifndef NEON_PGVERSIONCOMPAT_H
 #define NEON_PGVERSIONCOMPAT_H
 
+#include "fmgr.h"
+
 #if PG_MAJORVERSION_NUM < 17
 #define NRelFileInfoBackendIsTemp(rinfo) (rinfo.backend != InvalidBackendId)
 #else
@@ -123,4 +125,8 @@
 #define AmAutoVacuumWorkerProcess() (IsAutoVacuumWorkerProcess())
 #endif
 
+#if PG_MAJORVERSION_NUM < 15
+extern void InitMaterializedSRF(FunctionCallInfo fcinfo, bits32 flags);
+#endif
+
 #endif							/* NEON_PGVERSIONCOMPAT_H */

pgxn/neon/pagestore_smgr.c

@@ -66,6 +66,7 @@
 #include "storage/md.h"
 #include "storage/smgr.h"
 
+#include "neon_perf_counters.h"
 #include "pagestore_client.h"
 #include "bitmap.h"
 
@@ -289,7 +290,6 @@ static PrefetchState *MyPState;
 
 static bool compact_prefetch_buffers(void);
 static void consume_prefetch_responses(void);
-static uint64 prefetch_register_buffer(BufferTag tag, neon_request_lsns *force_request_lsns);
 static bool prefetch_read(PrefetchRequest *slot);
 static void prefetch_do_request(PrefetchRequest *slot, neon_request_lsns *force_request_lsns);
 static bool prefetch_wait_for(uint64 ring_index);
@@ -780,21 +780,27 @@ prefetch_do_request(PrefetchRequest *slot, neon_request_lsns *force_request_lsns
 }
 
 /*
- * prefetch_register_buffer() - register and prefetch buffer
+ * prefetch_register_bufferv() - register and prefetch buffers
  *
  * Register that we may want the contents of BufferTag in the near future.
+ * This is used when issuing a speculative prefetch request, but also when
+ * performing a synchronous request and need the buffer right now.
  *
  * If force_request_lsns is not NULL, those values are sent to the
  * pageserver. If NULL, we utilize the lastWrittenLsn -infrastructure
  * to calculate the LSNs to send.
  *
+ * When performing a prefetch rather than a synchronous request,
+ * is_prefetch==true. Currently, it only affects how the request is accounted
+ * in the perf counters.
+ *
  * NOTE: this function may indirectly update MyPState->pfs_hash; which
  * invalidates any active pointers into the hash table.
  */
-
 static uint64
 prefetch_register_bufferv(BufferTag tag, neon_request_lsns *frlsns,
-						  BlockNumber nblocks, const bits8 *mask)
+						  BlockNumber nblocks, const bits8 *mask,
+						  bool is_prefetch)
 {
 	uint64		min_ring_index;
 	PrefetchRequest req;
@@ -815,6 +821,7 @@ Retry:
 		PrfHashEntry *entry = NULL;
 		uint64		ring_index;
 		neon_request_lsns *lsns;
+
 		if (PointerIsValid(mask) && !BITMAP_ISSET(mask, i))
 			continue;
 
@@ -858,6 +865,7 @@ Retry:
 					prefetch_set_unused(ring_index);
 					entry = NULL;
 					slot = NULL;
+					MyNeonCounters->getpage_prefetch_discards_total++;
 				}
 			}
 
@@ -972,6 +980,11 @@ Retry:
 
 		min_ring_index = Min(min_ring_index, ring_index);
 
+		if (is_prefetch)
+			MyNeonCounters->getpage_prefetch_requests_total++;
+		else
+			MyNeonCounters->getpage_sync_requests_total++;
+
 		prefetch_do_request(slot, lsns);
 	}
 
@@ -1000,13 +1013,6 @@ Retry:
 }
 
 
-static uint64
-prefetch_register_buffer(BufferTag tag, neon_request_lsns *force_request_lsns)
-{
-	return prefetch_register_bufferv(tag, force_request_lsns, 1, NULL);
-}
-
-
 /*
  * Note: this function can get canceled and use a long jump to the next catch
  * context. Take care.
@@ -2612,7 +2618,7 @@ neon_prefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 			lfc_present[i] = ~(lfc_present[i]);
 
 		ring_index = prefetch_register_bufferv(tag, NULL, iterblocks,
-											   lfc_present);
+											   lfc_present, true);
 		nblocks -= iterblocks;
 		blocknum += iterblocks;
 
@@ -2656,7 +2662,7 @@ neon_prefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum)
 
 	CopyNRelFileInfoToBufTag(tag, InfoFromSMgrRel(reln));
 
-	ring_index = prefetch_register_buffer(tag, NULL);
+	ring_index = prefetch_register_bufferv(tag, NULL, 1, NULL, true);
 
 	Assert(ring_index < MyPState->ring_unused &&
 		   MyPState->ring_last <= ring_index);
@@ -2747,17 +2753,20 @@ neon_read_at_lsnv(NRelFileInfo rinfo, ForkNumber forkNum, BlockNumber base_block
 	 * weren't for the behaviour of the LwLsn cache that uses the highest
 	 * value of the LwLsn cache when the entry is not found.
 	 */
-	prefetch_register_bufferv(buftag, request_lsns, nblocks, mask);
+	prefetch_register_bufferv(buftag, request_lsns, nblocks, mask, false);
 
 	for (int i = 0; i < nblocks; i++)
 	{
 		void	   *buffer = buffers[i];
 		BlockNumber blockno = base_blockno + i;
 		neon_request_lsns *reqlsns = &request_lsns[i];
+		TimestampTz		start_ts, end_ts;
 
 		if (PointerIsValid(mask) && !BITMAP_ISSET(mask, i))
 			continue;
 
+		start_ts = GetCurrentTimestamp();
+
 		if (RecoveryInProgress() && MyBackendType != B_STARTUP)
 			XLogWaitForReplayOf(reqlsns[0].request_lsn);
 
@@ -2794,6 +2803,7 @@ Retry:
 				/* drop caches */
 				prefetch_set_unused(slot->my_ring_index);
 				pgBufferUsage.prefetch.expired += 1;
+				MyNeonCounters->getpage_prefetch_discards_total++;
 				/* make it look like a prefetch cache miss */
 				entry = NULL;
 			}
@@ -2804,8 +2814,9 @@ Retry:
 			if (entry == NULL)
 			{
 				pgBufferUsage.prefetch.misses += 1;
+				MyNeonCounters->getpage_prefetch_misses_total++;
 
-				ring_index = prefetch_register_bufferv(buftag, reqlsns, 1, NULL);
+				ring_index = prefetch_register_bufferv(buftag, reqlsns, 1, NULL, false);
 				Assert(ring_index != UINT64_MAX);
 				slot = GetPrfSlot(ring_index);
 			}
@@ -2860,6 +2871,9 @@ Retry:
 		/* buffer was used, clean up for later reuse */
 		prefetch_set_unused(ring_index);
 		prefetch_cleanup_trailing_unused();
+
+		end_ts = GetCurrentTimestamp();
+		inc_getpage_wait(end_ts >= start_ts ? (end_ts - start_ts) : 0);
 	}
 }
 
@@ -2913,6 +2927,7 @@ neon_read(SMgrRelation reln, ForkNumber forkNum, BlockNumber blkno, void *buffer
 	/* Try to read from local file cache */
 	if (lfc_read(InfoFromSMgrRel(reln), forkNum, blkno, buffer))
 	{
+		MyNeonCounters->file_cache_hits_total++;
 		return;
 	}
 
@@ -3097,7 +3112,7 @@ neon_readv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 				/* assume heap */
 				RmgrTable[RM_HEAP_ID].rm_mask(mdbuf_masked, blkno);
 				RmgrTable[RM_HEAP_ID].rm_mask(pageserver_masked, blkno);
-	
+
 				if (memcmp(mdbuf_masked, pageserver_masked, BLCKSZ) != 0)
 				{
 					neon_log(PANIC, "heap buffers differ at blk %u in rel %u/%u/%u fork %u (request LSN %X/%08X):\n------ MD ------\n%s\n------ Page Server ------\n%s\n",

test_runner/regress/test_compute_metrics.py

@@ -0,0 +1,21 @@
+from fixtures.neon_fixtures import NeonEnv
+
+
+def test_compute_metrics(neon_simple_env: NeonEnv):
+    """
+    Test compute metrics, exposed in the neon_backend_perf_counters and
+    neon_perf_counters views
+    """
+    env = neon_simple_env
+    endpoint = env.endpoints.create_start("main")
+
+    conn = endpoint.connect()
+    cur = conn.cursor()
+
+    # We don't check that the values make sense, this is just a very
+    # basic check that the server doesn't crash or something like that.
+    #
+    # 1.5 is the minimum version to contain these views.
+    cur.execute("CREATE EXTENSION neon VERSION '1.5'")
+    cur.execute("SELECT * FROM neon_perf_counters")
+    cur.execute("SELECT * FROM neon_backend_perf_counters")

test_runner/regress/test_neon_extension.py

@@ -50,8 +50,8 @@ def test_neon_extension_compatibility(neon_env_builder: NeonEnvBuilder):
             # Ensure that the default version is also updated in the neon.control file
             assert cur.fetchone() == ("1.4",)
             cur.execute("SELECT * from neon.NEON_STAT_FILE_CACHE")
-            all_versions = ["1.4", "1.3", "1.2", "1.1", "1.0"]
-            current_version = "1.4"
+            all_versions = ["1.5", "1.4", "1.3", "1.2", "1.1", "1.0"]
+            current_version = "1.5"
             for idx, begin_version in enumerate(all_versions):
                 for target_version in all_versions[idx + 1 :]:
                     if current_version != begin_version: