On 2015-09-15 08:07:57 -0500, Merlin Moncure wrote: > Are you confident this is faster across all workloads?
No. This is a proof of concept I just wrote & posted because I didn't see the patch moving in the right direction. But I do think it can be made faster in all relevant workloads. > Pin/Unpin are probably faster but this comes at a cost of extra atomic > ops during the clock sweep loop. I wonder if this will degrade > results under heavy contention. I think it's actually going to be faster under contention, and the situation where it's slower is uncontended workloads where you a very very low cache hit ratio. > Also, I'm curious about your introduction of __builtin_expect() > macros. Did you measure any gain from them? I introduced them because I was bothered by the generated assembler ;) But a bit more seriously, I do think there's some benefit in influencing the code like that. I personally also find they *increase* readability in cases like this where the likely() branch should be taken just about all the time. > I bet there are other places they could be used -- for example the > mvcc hint bit checks on xmin. I don't think those are good candidates, there's too many cases where it's common to have the majority of cases go the other way. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
