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.
> 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
