On 2017-10-30 22:39:01 +1300, David Rowley wrote: > On 30 October 2017 at 22:34, Andres Freund <and...@anarazel.de> wrote: > > Hi, > > > > On 2015-12-20 02:49:13 +1300, David Rowley wrote: > >> Alternatively, if there was some way to mark the path as cold from within > >> the path, rather than from the if() condition before the path, then we > >> could perhaps do something in the elog() macro instead. I just couldn't > >> figure out a way to do this. > > > > I just was thinking about this, and it turns out that > > __attribute__((cold)) does what we need here. We could just mark > > elog_start() and errstart() as cold, and afaict that should do the > > trick. > > I had actually been thinking about this again today. I had previously > not thought __attribute__((cold)) would be a good idea since if we > mark elog_start() with that, then code paths with elog(NOTICE) and > elog(LOG) not to mention DEBUG would be marked as cold.
That's an issue, true. Although I'm not convinced it's particularly fatal - if you're ok with emitting debugging output in places it's probably not the hottest codepath in the first place. And profile guided optimization would overwrite hot/cold. But: > Today I was thinking, to get around that issue, we might be able to > generate another thin wrapper around elog_start() and mark that as > __attribute__((cold)) and fudge the macro a bit to call that function > instead if it can detect a compile time const level >= ERROR. I've not > looked at the code again to remind myself if that would be possible. Yes, that's what I was thinking too. Add a elog_fatal() wrapping elog_finish(), and move the if (__builtin_constant_p(elevel)) branch a bit earlier, and that should work. Similar with errstart_fatal() for ereport(). Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers