[PATCHES] pgstat cleanup: use palloc and AllocateFile

[Neil Conway]

This patch changes pgstat.c to use palloc(), AllocateFile() and
FreeFile() rather than malloc(), fopen() and fclose(), respectively.

I changed more_tabstat_space() (which is invoked at various times
indirectly throughout the backend) to allocate memory in its own private
memory context, rather than use malloc() -- we can't just use
CurrentMemoryContext because that may not be sufficiently long-lived.

Barring any objections I intend to apply this to HEAD tomorrow.

-Neil

--- src/backend/postmaster/pgstat.c
+++ src/backend/postmaster/pgstat.c
@@ -42,6 +42,7 @@
 #include "miscadmin.h"
 #include "postmaster/postmaster.h"
 #include "storage/backendid.h"
+#include "storage/fd.h"
 #include "storage/ipc.h"
 #include "storage/pg_shmem.h"
 #include "storage/pmsignal.h"
@@ -118,6 +119,7 @@
 
 static bool pgStatRunningInCollector = FALSE;
 
+static MemoryContext tabstatCxt = NULL;
 static int	pgStatTabstatAlloc = 0;
 static int	pgStatTabstatUsed = 0;
 static PgStat_MsgTabstat **pgStatTabstatMessages = NULL;
@@ -682,7 +683,7 @@
 /* --
  * pgstat_report_activity() -
  *
- *	Called in tcop/postgres.c to tell the collector what the backend
+ *	Called from tcop/postgres.c to tell the collector what the backend
  *	is actually doing (usually "" or the start of the query to
  *	be executed).
  * --
@@ -988,49 +988,44 @@
 /*
  * Create or enlarge the pgStatTabstatMessages array
  */
-static bool
+static void
 more_tabstat_space(void)
 {
 	PgStat_MsgTabstat *newMessages;
 	PgStat_MsgTabstat **msgArray;
 	int			newAlloc = pgStatTabstatAlloc + TABSTAT_QUANTUM;
 	int			i;
+	MemoryContext oldCxt;
 
+	if (tabstatCxt == NULL)
+		tabstatCxt = AllocSetContextCreate(TopMemoryContext,
+		   "per-backend statistics buffer",
+		   ALLOCSET_DEFAULT_MINSIZE,
+		   ALLOCSET_DEFAULT_INITSIZE,
+		   ALLOCSET_DEFAULT_MAXSIZE);
+
+	oldCxt = MemoryContextSwitchTo(tabstatCxt);
+
 	/* Create (another) quantum of message buffers */
 	newMessages = (PgStat_MsgTabstat *)
-		malloc(sizeof(PgStat_MsgTabstat) * TABSTAT_QUANTUM);
-	if (newMessages == NULL)
-	{
-		ereport(LOG,
-(errcode(ERRCODE_OUT_OF_MEMORY),
- errmsg("out of memory")));
-		return false;
-	}
+		palloc0(sizeof(PgStat_MsgTabstat) * TABSTAT_QUANTUM);
 
 	/* Create or enlarge the pointer array */
 	if (pgStatTabstatMessages == NULL)
 		msgArray = (PgStat_MsgTabstat **)
-			malloc(sizeof(PgStat_MsgTabstat *) * newAlloc);
+			palloc(sizeof(PgStat_MsgTabstat *) * newAlloc);
 	else
 		msgArray = (PgStat_MsgTabstat **)
-			realloc(pgStatTabstatMessages,
-	sizeof(PgStat_MsgTabstat *) * newAlloc);
-	if (msgArray == NULL)
-	{
-		free(newMessages);
-		ereport(LOG,
-(errcode(ERRCODE_OUT_OF_MEMORY),
- errmsg("out of memory")));
-		return false;
-	}
+			repalloc(pgStatTabstatMessages,
+	 sizeof(PgStat_MsgTabstat *) * newAlloc);
 
-	MemSet(newMessages, 0, sizeof(PgStat_MsgTabstat) * TABSTAT_QUANTUM);
 	for (i = 0; i < TABSTAT_QUANTUM; i++)
 		msgArray[pgStatTabstatAlloc + i] = newMessages++;
 	pgStatTabstatMessages = msgArray;
 	pgStatTabstatAlloc = newAlloc;
 
-	return true;
+	Assert(pgStatTabstatUsed < pgStatTabstatAlloc);
+	MemoryContextSwitchTo(oldCxt);
 }
 
 /* --
@@ -1102,14 +1097,7 @@
 	 * If we ran out of message buffers, we just allocate more.
 	 */
 	if (pgStatTabstatUsed >= pgStatTabstatAlloc)
-	{
-		if (!more_tabstat_space())
-		{
-			stats->no_stats = TRUE;
-			return;
-		}
-		Assert(pgStatTabstatUsed < pgStatTabstatAlloc);
-	}
+		more_tabstat_space();
 
 	/*
 	 * Use the first entry of the next message buffer.
@@ -1146,10 +1139,8 @@
 	 * new xact-counters.
 	 */
 	if (pgStatTabstatAlloc == 0)
-	{
-		if (!more_tabstat_space())
-			return;
-	}
+		more_tabstat_space();
+
 	if (pgStatTabstatUsed == 0)
 	{
 		pgStatTabstatUsed++;
@@ -1180,10 +1178,8 @@
 	 * new xact-counters.
 	 */
 	if (pgStatTabstatAlloc == 0)
-	{
-		if (!more_tabstat_space())
-			return;
-	}
+		more_tabstat_space();
+
 	if (pgStatTabstatUsed == 0)
 	{
 		pgStatTabstatUsed++;
@@ -1529,13 +1527,8 @@
 	/*
 	 * Create the known backends table
 	 */
-	pgStatBeTable = (PgStat_StatBeEntry *) malloc(
+	pgStatBeTable = (PgStat_StatBeEntry *) palloc0(
 			   sizeof(PgStat_StatBeEntry) * MaxBackends);
-	if (pgStatBeTable == NULL)
-		ereport(ERROR,
-(errcode(ERRCODE_OUT_OF_MEMORY),
-			 errmsg("out of memory in statistics collector --- abort")));
-	memset(pgStatBeTable, 0, sizeof(PgStat_StatBeEntry) * MaxBackends);
 
 	readPipe = pgStatPipe[0];
 
@@ -1804,11 +1799,7 @@
 	/*
 	 * Allocate the message buffer
 	 */
-	msgbuffer = (char *) malloc(PGSTAT_RECVBUFFERSZ);
-	if (msgbuffer == NULL)
-		ereport(ERROR,
-(errcode(ERRCODE_OUT_OF_MEMORY),
-			 errmsg("out of memory in statistics collector --- abort")));
+	msgbuffer = (char *) palloc(PGSTAT_RECVBUFFERSZ);
 
 	/*
 	 * Loop forever
@@ -2416,7 +2412,7 @@
 	 * simply return zero for anything and the collector simply starts
 	 * from scratch with empty counters.
 	 */
-	if ((fpin = fopen(pgStat_fname,

Re: [PATCHES] pgstat cleanup: use palloc and AllocateFile

[Tom Lane]

Neil Conway <[EMAIL PROTECTED]> writes:
> I changed more_tabstat_space() (which is invoked at various times
> indirectly throughout the backend) to allocate memory in its own private
> memory context, rather than use malloc() -- we can't just use
> CurrentMemoryContext because that may not be sufficiently long-lived.

I'd suggest just allocating the tabstat space in TopMemoryContext.  The
extra sub-context is useless overhead, since you don't actually use it
for management purposes.

regards, tom lane

---(end of broadcast)---
TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]

Re: [PATCHES] pgstat cleanup: use palloc and AllocateFile

[Neil Conway]

On Thu, 2004-10-28 at 02:20, Tom Lane wrote:
> I'd suggest just allocating the tabstat space in TopMemoryContext.  The
> extra sub-context is useless overhead, since you don't actually use it
> for management purposes.

I don't know why I didn't think of that :)

Patch applied with your suggested change.

-Neil



---(end of broadcast)---
TIP 3: if posting/reading through Usenet, please send an appropriate
  subscribe-nomail command to [EMAIL PROTECTED] so that your
  message can get through to the mailing list cleanly