Re: Regarding Postgres Dynamic Shared Memory (DSA)

Hi,

As Michael said, i'm creating DSA too early. Shared_Preload libraries are
loading prior to memory related stuff.

But i'm totally clueless how to solve my use case.

Please help me with any work around.

Thanks & Best Regards,
- Mahi

On Tue, May 23, 2017 at 5:52 PM, Mahi Gurram <teckymahi(at)gmail(dot)com> wrote:

> Hi Michael,
>
> Thanks for your response.
>
> All i'm building is In-Memory Index as an extension over Postgres.
>
> Postgres Indexes will get Insert calls and Read calls from various
> processes(typically client/connection process - forked processes to
> postmaster process). Hence i have to maintain my In-Memory index in shared
> memory.
>
> If i create DynamicSharedArea (DSA) in postmaster/main process, all these
> Client/Connection processes(In-Memory Index Processes) need not attach to
> that DSA using area handle. Because these are forked processes to
> postmaster/Main process and hence they automatically gets attached.
>
> Hence i'm trying to create DSA in _PG_init function as it is called by
> postmaster/main process.
>
> Hope this is clear.
>
> Thanks & Best Regards,
> - Mahi
>
>
> On Tue, May 23, 2017 at 5:30 PM, Michael Paquier <
> michael(dot)paquier(at)gmail(dot)com> wrote:
>
>> On Tue, May 23, 2017 at 6:42 AM, Mahi Gurram <teckymahi(at)gmail(dot)com> wrote:
>> > I'm building In-Memory index extension for Postgres, for which i'm
>> trying to
>> > use DSA. But ended with some issues, as it is not allowing me to create
>> > DSA(Dynamic Shared Area) in _PG_init function.
>> >
>> > Please refer my_PG_init code below:
>> >>
>> >> void
>> >> _PG_init(void)
>> >> {
>> >> area = dsa_create(LWLockNewTrancheId(), "CustomIndex_DSA");
>> >> area_handle = dsa_get_handle(area);
>> >> }
>> >
>> >
>> > Because of this code, Postgres is not starting. Not even giving any
>> error
>> > messages in pg logs. Hence, i'm totally clue less :(
>>
>> It seems to me that you are creating those too early. For example, for
>> a background worker process, DSA segments would likely be created in
>> the main process routine. Without understanding what you are trying to
>> achieve, it is hard to make a good answer. You could always use a
>> ramdisk, but that would be likely be a waste of memory as Postgres has
>> its own buffer pool, killing the performance gains of OS caching.
>> --
>> Michael
>>
>
>