Re: semget: No space left on device

on 5/9/03 3:09 PM, andrew(at)libertyrms(dot)info purportedly said:

> On Fri, May 09, 2003 at 12:36:23PM -0600, Keary Suska wrote:
>> I do I get the dreaded "semget: No space left on device" error. Where can I
>> find information on the relationship between max connections and buffers and
>> shared memory/semaphores? I thought Bruce Momjian's performance tuning white
>
> I'd have a look in the manual itself:
>
> <http://www.us.postgresql.org/users-lounge/docs/7.3/postgres/runtime.html>
>

Thanks for the link. According to the info, I shouldn't have any problems. I
am shooting for 96 connections, using 192 buffers. My SHMMAX is 32mb, and
the calculations show that I need 2mb minimal for this, so even with
significant overhead I am fine.

Other values:
#define SEMMNI 128 /* ? max # of semaphore identifiers */
#define SEMMSL 250 /* <= 512 max num of semaphores per id */
#define SEMMNS (SEMMNI*SEMMSL) /* ? max # of semaphores in system */
#define SEMOPM 32 /* ~ 100 max num of ops per semop call */
#define SEMVMX 32767 /* semaphore maximum value */

/* unused */
#define SEMUME SEMOPM /* max num of undo entries per process */
#define SEMMNU SEMMNS /* num of undo structures system wide */
#define SEMAEM (SEMVMX >> 1) /* adjust on exit max value */
#define SEMMAP SEMMNS /* # of entries in semaphore map */
#define SEMUSZ 20 /* sizeof struct sem_undo */

Don't see any problem here.

# ipcs -l

------ Shared Memory Limits --------
max number of segments = 128
max seg size (kbytes) = 32768
max total shared memory (kbytes) = 16777216
min seg size (bytes) = 1

------ Semaphore Limits --------
max number of arrays = 128
max semaphores per array = 250
max semaphores system wide = 32000
max ops per semop call = 32
semaphore max value = 32767

------ Messages: Limits --------
max queues system wide = 128
max size of message (bytes) = 4056
default max size of queue (bytes) = 16384

(just for grins)

Maybe some other app is hogging:

# ipcs -u

------ Shared Memory Status --------
segments allocated 2
pages allocated 314
pages resident 165
pages swapped 0
Swap performance: 1446 attempts 72 successes

------ Semaphore Status --------
used arrays = 127
allocated semaphores = 159

------ Messages: Status --------
allocated queues = 0
used headers = 0
used space = 0 bytes

Doesn't seem like it.

Any ideas?

PG 7.1.3 on RH 6.2 Kernel 2.2.14

Keary Suska
Esoteritech, Inc.
"Leveraging Open Source for a better Internet"