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/*-------------------------------------------------------------------------
*
* mcxtfuncs.c
* Functions to show backend memory context.
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/utils/adt/mcxtfuncs.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "mb/pg_wchar.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/builtins.h"
/* ----------
* The max bytes for showing identifiers of MemoryContext.
* ----------
*/
#define MEMORY_CONTEXT_IDENT_DISPLAY_SIZE 1024
/*
* PutMemoryContextsStatsTupleStore
* One recursion level for pg_get_backend_memory_contexts.
*/
static void
PutMemoryContextsStatsTupleStore(Tuplestorestate *tupstore,
TupleDesc tupdesc, MemoryContext context,
const char *parent, int level)
{
#define PG_GET_BACKEND_MEMORY_CONTEXTS_COLS 9
Datum values[PG_GET_BACKEND_MEMORY_CONTEXTS_COLS];
bool nulls[PG_GET_BACKEND_MEMORY_CONTEXTS_COLS];
MemoryContextCounters stat;
MemoryContext child;
const char *name;
const char *ident;
Assert(MemoryContextIsValid(context));
name = context->name;
ident = context->ident;
/*
* To be consistent with logging output, we label dynahash contexts with
* just the hash table name as with MemoryContextStatsPrint().
*/
if (ident && strcmp(name, "dynahash") == 0)
{
name = ident;
ident = NULL;
}
/* Examine the context itself */
memset(&stat, 0, sizeof(stat));
(*context->methods->stats) (context, NULL, (void *) &level, &stat, true);
memset(values, 0, sizeof(values));
memset(nulls, 0, sizeof(nulls));
if (name)
values[0] = CStringGetTextDatum(name);
else
nulls[0] = true;
if (ident)
{
int idlen = strlen(ident);
char clipped_ident[MEMORY_CONTEXT_IDENT_DISPLAY_SIZE];
/*
* Some identifiers such as SQL query string can be very long,
* truncate oversize identifiers.
*/
if (idlen >= MEMORY_CONTEXT_IDENT_DISPLAY_SIZE)
idlen = pg_mbcliplen(ident, idlen, MEMORY_CONTEXT_IDENT_DISPLAY_SIZE - 1);
memcpy(clipped_ident, ident, idlen);
clipped_ident[idlen] = '\0';
values[1] = CStringGetTextDatum(clipped_ident);
}
else
nulls[1] = true;
if (parent)
values[2] = CStringGetTextDatum(parent);
else
nulls[2] = true;
values[3] = Int32GetDatum(level);
values[4] = Int64GetDatum(stat.totalspace);
values[5] = Int64GetDatum(stat.nblocks);
values[6] = Int64GetDatum(stat.freespace);
values[7] = Int64GetDatum(stat.freechunks);
values[8] = Int64GetDatum(stat.totalspace - stat.freespace);
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
for (child = context->firstchild; child != NULL; child = child->nextchild)
{
PutMemoryContextsStatsTupleStore(tupstore, tupdesc,
child, name, level + 1);
}
}
/*
* pg_get_backend_memory_contexts
* SQL SRF showing backend memory context.
*/
Datum
pg_get_backend_memory_contexts(PG_FUNCTION_ARGS)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
InitMaterializedSRF(fcinfo, 0);
PutMemoryContextsStatsTupleStore(rsinfo->setResult, rsinfo->setDesc,
TopMemoryContext, NULL, 0);
return (Datum) 0;
}
/*
* pg_log_backend_memory_contexts
* Signal a backend or an auxiliary process to log its memory contexts.
*
* By default, only superusers are allowed to signal to log the memory
* contexts because allowing any users to issue this request at an unbounded
* rate would cause lots of log messages and which can lead to denial of
* service. Additional roles can be permitted with GRANT.
*
* On receipt of this signal, a backend or an auxiliary process sets the flag
* in the signal handler, which causes the next CHECK_FOR_INTERRUPTS()
* or process-specific interrupt handler to log the memory contexts.
*/
Datum
pg_log_backend_memory_contexts(PG_FUNCTION_ARGS)
{
int pid = PG_GETARG_INT32(0);
PGPROC *proc;
BackendId backendId = InvalidBackendId;
proc = BackendPidGetProc(pid);
/*
* See if the process with given pid is a backend or an auxiliary process.
*
* If the given process is a backend, use its backend id in
* SendProcSignal() later to speed up the operation. Otherwise, don't do
* that because auxiliary processes (except the startup process) don't
* have a valid backend id.
*/
if (proc != NULL)
backendId = proc->backendId;
else
proc = AuxiliaryPidGetProc(pid);
/*
* BackendPidGetProc() and AuxiliaryPidGetProc() return NULL if the pid
* isn't valid; but by the time we reach kill(), a process for which we
* get a valid proc here might have terminated on its own. There's no way
* to acquire a lock on an arbitrary process to prevent that. But since
* this mechanism is usually used to debug a backend or an auxiliary
* process running and consuming lots of memory, that it might end on its
* own first and its memory contexts are not logged is not a problem.
*/
if (proc == NULL)
{
/*
* This is just a warning so a loop-through-resultset will not abort
* if one backend terminated on its own during the run.
*/
ereport(WARNING,
(errmsg("PID %d is not a PostgreSQL server process", pid)));
PG_RETURN_BOOL(false);
}
if (SendProcSignal(pid, PROCSIG_LOG_MEMORY_CONTEXT, backendId) < 0)
{
/* Again, just a warning to allow loops */
ereport(WARNING,
(errmsg("could not send signal to process %d: %m", pid)));
PG_RETURN_BOOL(false);
}
PG_RETURN_BOOL(true);
}
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