|
SEMMNI
Maximum number of semaphore identifiers (i.e., sets)
- at least ceil(num_os_semaphores / 19) plus room for other applications
+ at least ceil(num_os_semaphores / 16) plus room for other applications
|
SEMMNS
Maximum number of semaphores system-wide
- ceil(num_os_semaphores / 19) * 20 plus room for other applications
+ ceil(num_os_semaphores / 16) * 17 plus room for other applications
|
SEMMSL
Maximum number of semaphores per set
- at least 20
+ at least 17
|
(), allowed autovacuum worker process
(), allowed WAL sender process
(), allowed background
- process (), etc., in sets of 19.
+ process (), etc., in sets of 16.
The runtime-computed parameter
reports the number of semaphores required. This parameter can be viewed
before starting the server with a postgres command like:
- Each set of 19 semaphores will
- also contain a 20th semaphore which contains a magic
+ Each set of 16 semaphores will
+ also contain a 17th semaphore which contains a magic
number, to detect collision with semaphore sets used by
other applications. The maximum number of semaphores in the system
is set by SEMMNS, which consequently must be at least
as high as num_os_semaphores plus one extra for
- each set of 1
9 required semaphores (see the formula in
+ each set of 1
6 required semaphores (see the formula in
linkend="sysvipc-parameters"/>). The parameter SEMMNI
determines the limit on the number of semaphore sets that can
exist on the system at one time. Hence this parameter must be at
- least ceil(num_os_semaphores / 19).
+ least ceil(num_os_semaphores / 16).
Lowering the number
of allowed connections is a temporary workaround for failures,
which are usually confusingly worded No space
The default shared memory settings are usually good enough, unless
you have set shared_memory_type to sysv.
- You will usually want to increase kern.ipc.semmni
+ However, you will need to increase kern.ipc.semmni
and kern.ipc.semmns,
as NetBSD's default settings
- for these are uncomfortably small.
+ for these are unworkably small.
The default shared memory settings are usually good enough, unless
you have set shared_memory_type to sysv.
- You will usually want to
+ However, you will need to
increase kern.seminfo.semmni
and kern.seminfo.semmns,
as OpenBSD's default settings
- for these are uncomfortably small.
+ for these are unworkably small.
* we allocate. It must be *less than* your kernel's SEMMSL (max semaphores
* per set) parameter, which is often around 25. (Less than, because we
* allocate one extra sema in each set for identification purposes.)
- *
- * The present value of 19 is chosen with one eye on NetBSD/OpenBSD's default
- * SEMMNS setting of 60. Remembering the extra sema per set, this lets us
- * allocate three sets with 57 useful semaphores before exceeding that, which
- * is enough to run our core regression tests. Users of those systems will
- * still want to raise SEMMNS for any sort of production work, though.
*/
-#define SEMAS_PER_SET 19
+#define SEMAS_PER_SET 16
#define IPCProtection (0600) /* access/modify by user only */
* for a given max_connections value. Note that it has been carefully
* crafted to provide specific values for the associated values in
* trial_conns. We want it to return autovacuum_worker_slots's initial
- * default value (16) for the maximum value in trial_conns (100), and we
- * want it to return close to the minimum value we'd consider (3, which is
- * the default of autovacuum_max_workers) for the minimum value in
- * trial_conns (25).
+ * default value (16) for the maximum value in trial_conns[] (100), while
+ * it mustn't return less than the default value of autovacuum_max_workers
+ * (3) for the minimum value in trial_conns[].
*/
#define AV_SLOTS_FOR_CONNS(nconns) ((nconns) / 6)
static const int trial_conns[] = {
- 100, 50, 40, 30, 25
+ 100, 50, 40, 30, 20
};
static const int trial_bufs[] = {
16384, 8192, 4096, 3584, 3072, 2560, 2048, 1536,
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