On 13.02.2019 19:57, Tom Lane wrote:
Andres Freund <and...@anarazel.de> writes:
On February 13, 2019 1:16:07 PM GMT+01:00, Peter Eisentraut
<peter.eisentr...@2ndquadrant.com> wrote:
One idea to address this is to slow down WAL-generating maintenance
operations. This is similar to the vacuum delay. Where the vacuum
delay counts notional I/O cost before sleeping, here we would count how
much WAL has been generated and sleep after some amount.
Interesting idea, not yet quite sure what to think. But I don't think the way
you did it is acceptable - we can't just delay while holding buffer locks, in
critical sections, while not interruptible.
Yeah. Maybe it could be done in a less invasive way by just having the
WAL code keep a running sum of how much WAL this process has created,
and then letting the existing vacuum-delay infrastructure use that as
one of its how-much-IO-have-I-done inputs.
Not sure if that makes the tuning problem easier or harder, but
it seems reasonable on its face to count WAL emission as I/O.
regards, tom lane
Also we can add a 'soft' clause to DML queries. It will some abstraction
for background query execution. It can contain the WAL write velocity
limit parameter (as Tom proposed) and may some another.
--
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company
