Horton

Re: Changing shared_buffers without restart

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Thom Brown <thom@linux.com>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, Tomas Vondra <tomas@vondra.me>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Jack Ng <Jack.Ng@huawei.com>, Ni Ku <jakkuniku@gmail.com>
Date: 2025-07-14T13:14:26Z
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 →

  1. Remove PG_MMAP_FLAGS from mem.h

  2. Improve runtime and output of tests for replication slots checkpointing.

  3. Revert support for improved tracking of nested queries

  4. Use exported symbols list on macOS for loadable modules as well

  5. Add support for basic NUMA awareness

  6. Avoid unnecessary copying of a string in pg_restore.c

  7. aio: Infrastructure for io_method=worker

  8. Improve InitShmemAccess() prototype

Hi,

On 2025-07-14 15:08:28 +0200, Dmitry Dolgov wrote:
> > On Mon, Jul 14, 2025 at 08:56:56AM -0400, Andres Freund wrote:
> > > Ah, I see what you mean folks. But I'm talking here only about buffers
> > > which will be allocated after extending shared memory -- they  must go
> > > through the freelist first (I don't see why not, any other options?),
> > > and clock sweep will have a chance to pick them up only afterwards. That
> > > makes the freelist sort of an entry point for those buffers.
> >
> > Clock sweep can find any buffer, independent of whether it's on the freelist.
> 
> It does the search based on nextVictimBuffer, where the actual buffer
> will be a modulo of NBuffers, right? If that's correct and I get
> everything else right, that would mean as long as NBuffers stays the
> same (which is the case for the purposes of the current discussion) new
> buffers, allocated on top of NBuffers after shared memory increase, will
> not be picked by the clock sweep.

Are you tell me that you'd put "new" buffers onto the freelist, before you
increase NBuffers? That doesn't make sense.

Orthogonaly - there's discussion about simply removing the freelist.

Greetings,

Andres Freund