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Teach autoprewarm to use the dynamic shared memory registry.

Browse Source 
Besides showcasing the DSM registry, this prevents pg_prewarm from
stealing from the main shared memory segment's extra buffer space
when autoprewarm_start_worker() and autoprewarm_dump_now() are used
without loading the module via shared_preload_libraries.

Suggested-by: Michael Paquier
Reviewed-by: Bharath Rupireddy
Discussion: https://postgr.es/m/20231205034647.GA2705267%40nathanxps13
This commit is contained in:
Nathan Bossart 2024-01-19 14:43:59 -06:00
parent 8b2bcf3f28
commit abb0b4fc03
1 changed files with 15 additions and 31 deletions
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42
contrib/pg_prewarm/autoprewarm.c
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@ -32,12 +32,12 @@
#include "access/xact.h"
#include "catalog/pg_class.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/bgworker.h"
#include "postmaster/interrupt.h"
#include "storage/buf_internals.h"
#include "storage/dsm.h"
#include "storage/dsm_registry.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/latch.h"
@ -95,8 +95,6 @@ static void apw_start_database_worker(void);
static bool apw_init_shmem(void);
static void apw_detach_shmem(int code, Datum arg);
static int apw_compare_blockinfo(const void *p, const void *q);
static void autoprewarm_shmem_request(void);
static shmem_request_hook_type prev_shmem_request_hook = NULL;
/* Pointer to shared-memory state. */
static AutoPrewarmSharedState *apw_state = NULL;
@ -140,26 +138,11 @@ _PG_init(void)
MarkGUCPrefixReserved("pg_prewarm");
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = autoprewarm_shmem_request;
/* Register autoprewarm worker, if enabled. */
if (autoprewarm)
apw_start_leader_worker();
}
/*
* Requests any additional shared memory required for autoprewarm.
*/
static void
autoprewarm_shmem_request(void)
{
if (prev_shmem_request_hook)
prev_shmem_request_hook();
RequestAddinShmemSpace(MAXALIGN(sizeof(AutoPrewarmSharedState)));
}
/*
* Main entry point for the leader autoprewarm process. Per-database workers
* have a separate entry point.
@ -767,6 +750,16 @@ autoprewarm_dump_now(PG_FUNCTION_ARGS)
PG_RETURN_INT64((int64) num_blocks);
}
static void
apw_init_state(void *ptr)
{
AutoPrewarmSharedState *state = (AutoPrewarmSharedState *) ptr;
LWLockInitialize(&state->lock, LWLockNewTrancheId());
state->bgworker_pid = InvalidPid;
state->pid_using_dumpfile = InvalidPid;
}
/*
* Allocate and initialize autoprewarm related shared memory, if not already
* done, and set up backend-local pointer to that state. Returns true if an
@ -777,19 +770,10 @@ apw_init_shmem(void)
{
bool found;
LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
apw_state = ShmemInitStruct("autoprewarm",
apw_state = GetNamedDSMSegment("autoprewarm",
sizeof(AutoPrewarmSharedState),
apw_init_state,
&found);
if (!found)
{
/* First time through ... */
LWLockInitialize(&apw_state->lock, LWLockNewTrancheId());
apw_state->bgworker_pid = InvalidPid;
apw_state->pid_using_dumpfile = InvalidPid;
}
LWLockRelease(AddinShmemInitLock);
LWLockRegisterTranche(apw_state->lock.tranche, "autoprewarm");
return found;