On Sat, Apr 22, 2006 at 01:17:08PM -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > I still do, for multi-user systems. Releasing unused memory from a large > > CREATE INDEX will allow that memory to be swapped out, even if the brk > > point can't be changed. > > Say what? It can get "swapped out" anyway, whether we free() it or not. > > More to the point, though: I don't believe that the proposed patch is a > good idea --- it does not reduce the peak sortmem use, which I think is > the critical factor for a multiuser system, and what it does do is > reduce the locality of access to the sort temp file during the merge > phases. That will definitely have some impact; maybe small, but some; > and I don't see where the benefit comes in.
Do we have any info on how long the final phase of a sort typically takes compared to the rest of the sort? If it can take a substantial amount of time, then reducing the memory usage during that time will at least allow the OS to use that memory for caching again. In the future, if we have a better means of controlling sort memory usage, then freeing the memory earlier would also put it back in the pool earlier, which would benefit the multiple concurrent sorts case. -- Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq