On 26 August 2015 at 11:40, Amit Kapila <amit.kapil...@gmail.com> wrote:
> On Tue, Aug 25, 2015 at 2:21 PM, Simon Riggs <si...@2ndquadrant.com> > wrote: > >> On 22 August 2015 at 15:14, Andres Freund <and...@anarazel.de> wrote: >> > > >> TransactionIdSetPageStatus() calls TransactionIdSetStatusBit(), which >>> writes an 8 byte variable (the lsn). That's not safe. >>> >> >> Agreed, thanks for spotting that. >> >> I see this as the biggest problem to overcome with this patch. >> > > How about using 64bit atomics or spinlock to protect this variable? > Spinlock is out IMHO because this happens on every clog lookup. So it must be an atomic read. I'm wondering if its worth making this work on 32-bit systems at all. The contention problems only occur on higher end servers, so we can just disable this optimization if we aren't on a 64bit server. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
