Re: Improve WALRead() to suck data directly from WAL buffers when possible

Jeff Davis <pgsql@j-davis.com>

From: Jeff Davis <pgsql@j-davis.com>

To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>

Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, pgsql-hackers@lists.postgresql.org

Date: 2023-01-14T08:48:52Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Add XLogCtl->logInsertResult
- f3ff7bf83bce 17.0 cited
Add assert to WALReadFromBuffers().
- 9ecbf54075a9 17.0 landed
Read WAL directly from WAL buffers.
- 91f2cae7a4e6 17.0 landed
Additional write barrier in AdvanceXLInsertBuffer().
- 766571be1659 17.0 landed
Use 64-bit atomics for xlblocks array elements.
- c3a8e2a7cb16 17.0 landed
Don't trust unvalidated xl_tot_len.
- bae868caf222 17.0 cited

On Mon, 2022-12-26 at 14:20 +0530, Bharath Rupireddy wrote:
> Please review the attached v2 patch further.

I'm still unclear on the performance goals of this patch. I see that it
will reduce syscalls, which sounds good, but to what end?

Does it allow a greater number of walsenders? Lower replication
latency? Less IO bandwidth? All of the above?


-- 
Jeff Davis
PostgreSQL Contributor Team - AWS