On Thu, Apr 7, 2016 at 4:41 PM, Andres Freund <and...@anarazel.de> wrote:
> On 2016-03-31 20:21:02 +0300, Alexander Korotkov wrote: > > ! BEGIN_BUFSTATE_CAS_LOOP(bufHdr); > > > > ! Assert(BUF_STATE_GET_REFCOUNT(state) > 0); > > ! wasDirty = (state & BM_DIRTY) ? true : false; > > ! state |= BM_DIRTY | BM_JUST_DIRTIED; > > ! if (state == oldstate) > > ! break; > > I'm doubtful that this early exit is entirely safe. None of the > preceding operations imply a memory barrier. The buffer could previously > have been marked dirty, but cleaned since. It's pretty critical that we > re-set the dirty bit (there's no danger of loosing it with a barrier, > because we hold an exclusive content lock). > Oh, I get it. > Practically the risk seems fairly low, because acquiring the exclusive > content lock will have implied a barrier. But it seems unlikely to have > a measurable performance effect to me, so I'd rather not add the early > exit. > Ok, let's just remove it. ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
