Re: WAL & SHM principles - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: WAL & SHM principles
Date
Msg-id 200103081645.LAA03243@candle.pha.pa.us
Whole thread Raw
In response to Re: WAL & SHM principles  (Martin Devera <devik@cdi.cz>)
Responses Re: WAL & SHM principles  (Martin Devera <devik@cdi.cz>)
List pgsql-hackers
> > > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > > > The only problem is that we would no longer have control over which
> > > > pages made it to disk.  The OS would perhaps write pages as we modified
> > > > them.  Not sure how important that is.
> > > 
> > > Unfortunately, this alone is a *fatal* objection.  See nearby
> > > discussions about WAL behavior: we must be able to control the relative
> > > timing of WAL write/flush and data page writes.
> > 
> > Bummer.
> > 
> BTW, what means "bummer" ?

Sorry, it means, "Oh, I am disappointed."

> But for many OSes you CAN control when to write data - you can mlock
> individual pages.

mlock() controls locking in physical memory.  I don't see it controling
write().

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026
 


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