Horton

Re: Refactoring the checkpointer's fsync request queue

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, sdn@amazon.com, Dmitry Dolgov <9erthalion6@gmail.com>
Date: 2018-11-14T21:49:48Z
Lists: pgsql-hackers 
On 2018-11-14 16:36:49 -0500, Robert Haas wrote:
> On Tue, Nov 13, 2018 at 6:44 PM Thomas Munro
> <thomas.munro@enterprisedb.com> wrote:
> > I'm not sure if it matters whether we send the fd before or after the
> > write, but we still need some kind of global ordering of fds that can
> > order a given fd with respect to writes in other processes, so the
> > patch introduces a global shared counter captured immediately after
> > open() (including when reopened in the vfd machinery).
> 
> But how do you make reading that counter atomic with the open() itself?

I don't see why it has to be. As long as the "fd generation" assignment
happens before fsync (and writes secondarily), there ought not to be any
further need for synchronizity?

Greetings,

Andres Freund

Commits

  1. Fix bugs in mdsyncfiletag().

  2. Refactor the fsync queue for wider use.

  3. Don't forget about failed fsync() requests.

  4. PANIC on fsync() failure.

  5. Move LockClauseStrength, LockWaitPolicy into new file nodes/lockoptions.h.

  6. Add new file for checkpointer.c

  7. Split work of bgwriter between 2 processes: bgwriter and checkpointer.

  8. Install infrastructure for shared-memory free space map. Doesn't actually