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Turn PGBE_ACTIVITY_SIZE into a GUC variable, track_activity_query_size.

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As the buffer could now be a lot larger than before, and copying it could
thus be a lot more expensive than before, use strcpy instead of memcpy to
copy the query string, as was already suggested in comments. Also, only copy
the PgBackendStatus struct and string if the slot is in use.

Patch by Thomas Lee, with some changes by me.
This commit is contained in:
Heikki Linnakangas
2008-06-30 10:58:47 +00:00
parent 7ea9b997ef
commit 995fb74202
5 changed files with 77 additions and 18 deletions
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57
src/backend/postmaster/pgstat.c
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@@ -13,7 +13,7 @@
*
* Copyright (c) 2001-2008, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.175 2008/06/19 00:46:05 alvherre Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.176 2008/06/30 10:58:47 heikki Exp $
* ----------
*/
#include "postgres.h"
@@ -101,6 +101,7 @@
bool pgstat_track_activities = false;
bool pgstat_track_counts = false;
int pgstat_track_functions = TRACK_FUNC_OFF;
int pgstat_track_activity_query_size = 1024;
/*
* BgWriter global statistics counters (unused in other processes).
@@ -2010,6 +2011,7 @@ pgstat_fetch_global(void)
static PgBackendStatus *BackendStatusArray = NULL;
static PgBackendStatus *MyBEEntry = NULL;
static char *BackendActivityBuffer = NULL;
/*
@@ -2020,20 +2022,25 @@ BackendStatusShmemSize(void)
{
Size size;
size = mul_size(sizeof(PgBackendStatus), MaxBackends);
size = add_size(mul_size(sizeof(PgBackendStatus), MaxBackends),
mul_size(pgstat_track_activity_query_size, MaxBackends));
return size;
}
/*
* Initialize the shared status array during postmaster startup.
* Initialize the shared status array and activity string buffer during
* postmaster startup.
*/
void
CreateSharedBackendStatus(void)
{
Size size = BackendStatusShmemSize();
Size size;
bool found;
int i;
char *buffer;
/* Create or attach to the shared array */
size = mul_size(sizeof(PgBackendStatus), MaxBackends);
BackendStatusArray = (PgBackendStatus *)
ShmemInitStruct("Backend Status Array", size, &found);
@@ -2044,6 +2051,23 @@ CreateSharedBackendStatus(void)
*/
MemSet(BackendStatusArray, 0, size);
}
/* Create or attach to the shared activity buffer */
size = mul_size(pgstat_track_activity_query_size, MaxBackends);
BackendActivityBuffer = (char*)
ShmemInitStruct("Backend Activity Buffer", size, &found);
if (!found)
{
MemSet(BackendActivityBuffer, 0, size);
/* Initialize st_activity pointers. */
buffer = BackendActivityBuffer;
for (i = 0; i < MaxBackends; i++) {
BackendStatusArray[i].st_activity = buffer;
buffer += pgstat_track_activity_query_size;
}
}
}
@@ -2128,7 +2152,7 @@ pgstat_bestart(void)
beentry->st_waiting = false;
beentry->st_activity[0] = '\0';
/* Also make sure the last byte in the string area is always 0 */
beentry->st_activity[PGBE_ACTIVITY_SIZE - 1] = '\0';
beentry->st_activity[pgstat_track_activity_query_size - 1] = '\0';
beentry->st_changecount++;
Assert((beentry->st_changecount & 1) == 0);
@@ -2188,7 +2212,7 @@ pgstat_report_activity(const char *cmd_str)
start_timestamp = GetCurrentStatementStartTimestamp();
len = strlen(cmd_str);
len = pg_mbcliplen(cmd_str, len, PGBE_ACTIVITY_SIZE - 1);
len = pg_mbcliplen(cmd_str, len, pgstat_track_activity_query_size - 1);
/*
* Update my status entry, following the protocol of bumping
@@ -2267,6 +2291,7 @@ pgstat_read_current_status(void)
volatile PgBackendStatus *beentry;
PgBackendStatus *localtable;
PgBackendStatus *localentry;
char *localactivity;
int i;
Assert(!pgStatRunningInCollector);
@@ -2278,6 +2303,9 @@ pgstat_read_current_status(void)
localtable = (PgBackendStatus *)
MemoryContextAlloc(pgStatLocalContext,
sizeof(PgBackendStatus) * MaxBackends);
localactivity = (char *)
MemoryContextAlloc(pgStatLocalContext,
pgstat_track_activity_query_size * MaxBackends);
localNumBackends = 0;
beentry = BackendStatusArray;
@@ -2295,11 +2323,17 @@ pgstat_read_current_status(void)
{
int save_changecount = beentry->st_changecount;
/*
* XXX if PGBE_ACTIVITY_SIZE is really large, it might be best to
* use strcpy not memcpy for copying the activity string?
*/
memcpy(localentry, (char *) beentry, sizeof(PgBackendStatus));
localentry->st_procpid = beentry->st_procpid;
if (localentry->st_procpid > 0)
{
memcpy(localentry, (char *) beentry, sizeof(PgBackendStatus));
/*
* strcpy is safe even if the string is modified concurrently,
* because there's always a \0 at the end of the buffer.
*/
strcpy(localactivity, (char *) beentry->st_activity);
localentry->st_activity = localactivity;
}
if (save_changecount == beentry->st_changecount &&
(save_changecount & 1) == 0)
@@ -2314,6 +2348,7 @@ pgstat_read_current_status(void)
if (localentry->st_procpid > 0)
{
localentry++;
localactivity += pgstat_track_activity_query_size;
localNumBackends++;
}
}