From: | Alexander Kuzmenkov <a(dot)kuzmenkov(at)postgrespro(dot)ru> |
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To: | Rafia Sabih <rafia(dot)sabih(at)enterprisedb(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [POC] Faster processing at Gather node |
Date: | 2017-09-08 17:37:29 |
Message-ID: | eb17a29f-0a1b-a2ee-bf86-548b37945e5d@postgrespro.ru |
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Lists: | pgsql-hackers |
Hi Rafia,
I like the idea of reducing locking overhead by sending tuples in bulk.
The implementation could probably be simpler: you could extend the API
of shm_mq to decouple notifying the sender from actually putting data
into the queue (i.e., make shm_mq_notify_receiver public and make a
variant of shm_mq_sendv that doesn't send the notification). From Amit's
letter I understand that you have already tried something along these
lines and the performance wasn't good. What was the bottleneck then? If
it's the locking around mq_bytes_read/written, it can be rewritten with
atomics. I think it would be great to try this approach because it
doesn't add much code, doesn't add any additional copying and improves
shm_mq performance in general.
--
Alexander Kuzmenkov
Postgres Professional:http://www.postgrespro.com
The Russian Postgres Company
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