In the last exciting episode, [EMAIL PROTECTED] (Josh Berkus) wrote: > So what is the ceiling on 32-bit processors for RAM? Most of the > 64-bit vendors are pushing Athalon64 and G5 as "breaking the 4GB > barrier", and even I can do the math on 2^32. All these 64-bit > vendors, then, are talking about the limit on ram *per application* > and not per machine?
I have been seeing ia-32 servers with 8GB of RAM; it looks as though there are ways of having them support ("physically, in theory, if you could get a suitable motherboard") as much as 64GB. But that certainly doesn't get you past 2^32 bytes per process, and possibly not past 2^31 bytes/process. >From Linux kernel help: CONFIG_NOHIGHMEM: Linux can use up to 64 Gigabytes of physical memory on x86 systems. However, the address space of 32-bit x86 processors is only 4 Gigabytes large. That means that, if you have a large amount of physical memory, not all of it can be "permanently mapped" by the kernel. The physical memory that's not permanently mapped is called "high memory". And that leaves open the question of how much shared memory you can address. That presumably has to fit into the 4GB, and if your PostgreSQL processes had (by some fluke) 4GB of shared memory, there wouldn't be any "local" memory for sort memory and the likes. Add to that the consideration that there are reports of Linux "falling over" when you get to right around 2GB/4GB. I ran a torture test a while back that _looked_ like it was running into that; I can't verify that, unfortunately. I don't see there being a whole lot of use of having more than about 8GB on an ia-32 system; what with shared memory maxing out at somewhere between 1 and 2GB, that suggests having ~8GB in total. I'd add another PG cluster if I had 16GB... -- let name="aa454" and tld="freenet.carleton.ca" in name ^ "@" ^ tld;; http://www.ntlug.org/~cbbrowne/postgresql.html "A statement is either correct or incorrect. To be *very* incorrect is like being *very* dead ... " -- Herbert F. Spirer Professor of Information Management University of Conn. (DATAMATION Letters, Sept. 1, 1984) ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster