2010/11/21 Andres Freund <and...@anarazel.de>: > On Sunday 21 November 2010 23:19:30 Martijn van Oosterhout wrote: >> For a similar problem we had (kernel buffering too much) we had success >> using the fadvise and madvise WONTNEED syscalls to force the data to >> exit the cache much sooner than it would otherwise. This was on Linux >> and it had the side-effect that the data was deleted from the kernel >> cache, which we wanted, but probably isn't appropriate here. > Yep, works fine. Although it has the issue that the data will get read again > if > archiving/SR is enabled.
mmhh . the current code does call DONTNEED or WILLNEED for WAL depending of the archiving off or on. This matters *only* once the data is writen (fsync, fdatasync), before that it should not have an effect. > >> There is also sync_file_range, but that's linux specific, although >> close to what you want I think. It would allow you to work with blocks >> smaller than 1GB. > Unfortunately that puts the data under quite high write-out pressure inside > the kernel - which is not what you actually want because it limits reordering > and such significantly. > > It would be nicer if you could get a mix of both semantics (looking at it, > depending on the approach that seems to be about a 10 line patch to the > kernel). I.e. indicate that you want to write the pages soonish, but don't put > it on the head of the writeout queue. > > Andres > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers > -- Cédric Villemain 2ndQuadrant http://2ndQuadrant.fr/ PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
