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* BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes
@ 2023-08-04 05:22 PG Bug reporting form <noreply@postgresql.org>
2023-08-04 13:22 ` Re: BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes Andrew Dunstan <andrew@dunslane.net>
0 siblings, 1 reply; 3+ messages in thread
From: PG Bug reporting form @ 2023-08-04 05:22 UTC (permalink / raw)
To: pgsql-bugs@lists.postgresql.org; +Cc: jkr0103@gmail.com
The following bug has been logged on the website:
Bug reference: 18049
Logged by: Jitender Kumar
Email address: jkr0103@gmail.com
PostgreSQL version: 12.1
Operating system: ubuntu 20.04
Description:
Expected `shm_open` syscall for the `posix` value of
`dynamic_shared_memory_type` parameter but strace shows `shm_get` being
executed.
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes
2023-08-04 05:22 BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes PG Bug reporting form <noreply@postgresql.org>
@ 2023-08-04 13:22 ` Andrew Dunstan <andrew@dunslane.net>
2023-08-07 14:38 ` Re: BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes jitu <jkr0103@gmail.com>
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Dunstan @ 2023-08-04 13:22 UTC (permalink / raw)
To: jkr0103@gmail.com; pgsql-bugs@lists.postgresql.org
On 2023-08-04 Fr 01:22, PG Bug reporting form wrote:
> The following bug has been logged on the website:
>
> Bug reference: 18049
> Logged by: Jitender Kumar
> Email address:jkr0103@gmail.com
> PostgreSQL version: 12.1
> Operating system: ubuntu 20.04
> Description:
>
> Expected `shm_open` syscall for the `posix` value of
> `dynamic_shared_memory_type` parameter but strace shows `shm_get` being
> executed.
>
src/backend/port/sysv_shmem. says:
* As of PostgreSQL 9.3, we normally allocate only a very small amount of
* System V shared memory, and only for the purposes of providing an
* interlock to protect the data directory.
while src/backend/storage/ipc/dsm_impl.c says:
* This file provides low-level APIs for creating and destroying shared
* memory segments using several different possible techniques. We refer
* to these segments as dynamic because they can be created, altered, and
* destroyed at any point during the server life cycle. This is unlike
* the main shared memory segment, of which there is always exactly one
* and which is always mapped at a fixed address in every PostgreSQL
* background process.
So AIUI you should always see a call like this when Postgres starts.
cheers
andrew
--
Andrew Dunstan
EDB:https://www.enterprisedb.com
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes
2023-08-04 05:22 BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes PG Bug reporting form <noreply@postgresql.org>
2023-08-04 13:22 ` Re: BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes Andrew Dunstan <andrew@dunslane.net>
@ 2023-08-07 14:38 ` jitu <jkr0103@gmail.com>
0 siblings, 0 replies; 3+ messages in thread
From: jitu @ 2023-08-07 14:38 UTC (permalink / raw)
To: Andrew Dunstan <andrew@dunslane.net>; +Cc: pgsql-bugs@lists.postgresql.org
Thanks Andrew for the response but I did not understand it.
Documentation here
https://postgresqlco.nf/doc/en/param/dynamic_shared_memory_type/ says for
`posix` value `shm_open` syscall should be generated which I don't see.
Also I added logline in `postgres/src/backend/storage/ipc/dsm_impl.c`
inside function `dsm_impl_op` to print `dynamic_shared_memory_type` value
which printed 1 (DSM_IMPL_POSIX). but still strace doesn't show `shm_open`
call.
On Fri, Aug 4, 2023 at 6:52 PM Andrew Dunstan <andrew@dunslane.net> wrote:
>
> On 2023-08-04 Fr 01:22, PG Bug reporting form wrote:
>
> The following bug has been logged on the website:
>
> Bug reference: 18049
> Logged by: Jitender Kumar
> Email address: jkr0103@gmail.com
> PostgreSQL version: 12.1
> Operating system: ubuntu 20.04
> Description:
>
> Expected `shm_open` syscall for the `posix` value of
> `dynamic_shared_memory_type` parameter but strace shows `shm_get` being
> executed.
>
>
>
> src/backend/port/sysv_shmem. says:
> * As of PostgreSQL 9.3, we normally allocate only a very small amount of
> * System V shared memory, and only for the purposes of providing an
> * interlock to protect the data directory.
>
> while src/backend/storage/ipc/dsm_impl.c says:
>
> * This file provides low-level APIs for creating and destroying shared
> * memory segments using several different possible techniques. We refer
> * to these segments as dynamic because they can be created, altered, and
> * destroyed at any point during the server life cycle. This is unlike
> * the main shared memory segment, of which there is always exactly one
> * and which is always mapped at a fixed address in every PostgreSQL
> * background process.
>
> So AIUI you should always see a call like this when Postgres starts.
>
>
>
> cheers
>
>
> andrew
>
>
> --
> Andrew Dunstan
> EDB: https://www.enterprisedb.com
>
>
^ permalink raw reply [nested|flat] 3+ messages in thread
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2023-08-04 05:22 BUG #18049: dynamic_shared_memory_type's value `posix` doesn't have any effect, syscall shm_get executes PG Bug reporting form <noreply@postgresql.org>
2023-08-04 13:22 ` Andrew Dunstan <andrew@dunslane.net>
2023-08-07 14:38 ` jitu <jkr0103@gmail.com>
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