Re: Parallel Seq Scan vs kernel read ahead - Mailing list pgsql-hackers

From Soumyadeep Chakraborty
Subject Re: Parallel Seq Scan vs kernel read ahead
Date
Msg-id CAE-ML+90Rn4o_-3JA3ZoWgg8qCx=JU_875QppjA21i4KesAkYg@mail.gmail.com
Whole thread Raw
In response to Re: Parallel Seq Scan vs kernel read ahead  (David Rowley <dgrowleyml@gmail.com>)
Responses Re: Parallel Seq Scan vs kernel read ahead
List pgsql-hackers
> It doesn't look like it's using table_block_parallelscan_nextpage() as
> a block allocator so it's not affected by the patch.  It has its own
> thing zs_parallelscan_nextrange(), which does
> pg_atomic_fetch_add_u64(&pzscan->pzs_allocatedtids,
> ZS_PARALLEL_CHUNK_SIZE), and that macro is 0x100000.

My apologies, I was too hasty. Indeed, you are correct. Zedstore's
unit of work is chunks of the logical zstid space. There is a
correlation between the zstid and blocks: zstids near each other are
likely to lie in the same block or in neighboring blocks. It would be
interesting to try something like this patch for Zedstore.

Regards,
Soumyadeep



pgsql-hackers by date:

Previous
From: Andres Freund
Date:
Subject: Re: SIGSEGV from START_REPLICATION 0/XXXXXXX in XLogSendPhysical ()at walsender.c:2762
Next
From: Soumyadeep Chakraborty
Date:
Subject: Re: Parallel Seq Scan vs kernel read ahead