Thread: compiling, performance of PostGreSQL 8.3 on 64-bit processors
Dear All, 1. I have heard of problems arising from compiling PostGreSQL (8.3) on 64-bit processors. What sort of problems am I likely to encounter and how should I fix them? We are will run Linux Redhat 5 on a Dell PE2950 III Quad Core Xeon E54 2.33 GHz, and a Dell PE2950 III Quad Core Xeon L5335 2.0 GHz. 2. Are there performance problems running PostGreSQL 8.3 on a 64-bit processor? Thanks in advance. Yours Ben Weaver -- Benjamin Weaver Faculty Research Associate, Imaging Papyri, Greek Fragments Projects, Oxford email: benjamin.weaver@classics.ox.ac.uk phone: (0)1865 610236
> 1. I have heard of problems arising from compiling PostGreSQL (8.3) on > 64-bit > processors. What sort of problems am I likely to encounter and how > should I fix > them? We are will run Linux Redhat 5 on a Dell PE2950 III Quad Core > Xeon E54 > 2.33 GHz, and a Dell PE2950 III Quad Core Xeon L5335 2.0 GHz. > > 2. Are there performance problems running PostGreSQL 8.3 on a 64-bit > processor? > I have a few more questions on the 64-bit topic. Is there any benefit to running a 32-bit OS (rhel 5 in this case) on a server with more than 4 GB of memory? In other words, can the OS-level cache take advantage of more than 4 GB of memory? Can a process (such as PG backend) use more than 4 GB of shared memory on a 32-bit OS? Or is the 4 GB memory point the place where you normally transition to a 64-bit OS? For people with experience running postgresql on systems with 16+ GB of memory, what parameter settings have you found to be effective? (This would be a large database that's mostly read-only that we'd like to fit completely in memory) Is it possible to backup (pg_dump) from a 32-bit OS to a 64-bit OS, or is a plain SQL dump necessary?
On Thu, 26 Jun 2008, Benjamin Weaver wrote: > I have heard of problems arising from compiling PostGreSQL (8.3) on > 64-bit processors. From who? > We are will run Linux Redhat 5 If there were any problems compiling and running PostgreSQL on 64-bit RHEL5, I wouldn't be writing this message right now because I'd be hiding from angry customers circling with torches and pitchforks. And Tom Lane would have already committed ritual suicide in shame. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
On Thu, Jun 26, 2008 at 7:12 PM, Adam Rich <adam.r@sbcglobal.net> wrote: > >> 1. I have heard of problems arising from compiling PostGreSQL (8.3) on >> 64-bit >> processors. What sort of problems am I likely to encounter and how >> should I fix >> them? We are will run Linux Redhat 5 on a Dell PE2950 III Quad Core >> Xeon E54 >> 2.33 GHz, and a Dell PE2950 III Quad Core Xeon L5335 2.0 GHz. >> >> 2. Are there performance problems running PostGreSQL 8.3 on a 64-bit >> processor? Should compile and run fine--I haven't heard of any problems with it, and PG has run on 64-bit systems (SGI, Sun, Alpha) long before there was x86_64. > I have a few more questions on the 64-bit topic. Is there any benefit > to running a 32-bit OS (rhel 5 in this case) on a server with more than > 4 GB of memory? In other words, can the OS-level cache take advantage > of more than 4 GB of memory? With a 32-bit kernel and >4GB of memory, you will indeed get more available to cache from the OS. It's generally not recommended to use more than 8GB with a 32-bit kernel. > Can a process (such as PG backend) use > more than 4 GB of shared memory on a 32-bit OS? No, and the practical limit is more like 2GB (or less). >Or is the 4 GB memory > point the place where you normally transition to a 64-bit OS? In this day and age there's not too much of a reason to run in 32 bits on a server capable of 64. If necessary, you can run 32-bit legacy binaries under a 64-bit kernel, if you set up the libraries properly. > For people with experience running postgresql on systems with 16+ GB > of memory, what parameter settings have you found to be effective? > (This would be a large database that's mostly read-only that we'd > like to fit completely in memory) Can't help with this one, sorry. > Is it possible to backup (pg_dump) from a 32-bit OS to a 64-bit OS, > or is a plain SQL dump necessary? pg_dump output (which by default *is* plain SQL, though there are two other formats) is compatible across architectures. Backups of the on-disk database files are not. -Doug
On Thu, 26 Jun 2008, Benjamin Weaver wrote: > Dear All, > > 1. I have heard of problems arising from compiling PostGreSQL (8.3) on 64-bit > processors. What sort of problems am I likely to encounter and how should I fix > them? We are will run Linux Redhat 5 on a Dell PE2950 III Quad Core Xeon E54 > 2.33 GHz, and a Dell PE2950 III Quad Core Xeon L5335 2.0 GHz. What problems have you heard? It's working quite well for us on our 64-bit Xeons, but maybe there are some snake zygotes hidden under rocks that we're unaware of.
Greg Smith <gsmith@gregsmith.com> writes:
> On Thu, 26 Jun 2008, Benjamin Weaver wrote:
>> I have heard of problems arising from compiling PostGreSQL (8.3) on
>> 64-bit processors.
> From who?
Perhaps someone who remembers PG 6.4 or thereabouts?
Certainly any version released in the last couple of years has been
tested about as heavily on 64-bit platforms as 32-bit.
regards, tom lane
Sorry, guys, for wasting bandwidth on this! You guys gave just the answer I wanted to hear. Sounds like there aren't any problems. Not knowing about such things, I was scared by the following quote. Perhaps binaries do not need to be compiled as 64 bit binaries on a 64 bit machine? Or perhaps it's way out of date (2004) or simply wrong. from http://www.osnews.com/story/5768/Are_64-bit_Binaries_Really_Slower_than_32-bit_Binaries_/page3/ " ... The Compile Factor Getting applications to compile as 64-bit binaries can be tricky. The build process for some applications, such as OpenSSL, have 64-bit specifically in mind, and require nothing fancy. Others, like MySQL and especially PostgreSQL (I was originally going to include PostgreSQL benchmarks) took quite a bit of tweaking. There are compiler flags, linker flags, and you'll likely end up in a position where you need to know your way around a Makefile..." In message <23234.1214523814@sss.pgh.pa.us> Tom Lane <tgl@sss.pgh.pa.us> writes: > Greg Smith <gsmith@gregsmith.com> writes: > > On Thu, 26 Jun 2008, Benjamin Weaver wrote: > >> I have heard of problems arising from compiling PostGreSQL (8.3) on > >> 64-bit processors. > > > From who? > > Perhaps someone who remembers PG 6.4 or thereabouts? > > Certainly any version released in the last couple of years has been > tested about as heavily on 64-bit platforms as 32-bit. > > regards, tom lane -- Benjamin Weaver Faculty Research Associate, Imaging Papyri, Greek Fragments Projects, Oxford email: benjamin.weaver@classics.ox.ac.uk phone: (0)1865 610236
"Douglas McNaught" <doug@mcnaught.org> writes:
> On Fri, Jun 27, 2008 at 11:52 AM, Benjamin Weaver
> <benjamin.weaver@classics.ox.ac.uk> wrote:
>> Not knowing about such things, I was scared by the following quote.
> Distro support for 64-bit x86 in 2004 was light-years behind where it
> is now. A lot of stuff was hard to get working back then. Now almost
> everything basically Just Works.
Even in 2004, the guy would have had to be working on a rather old or
broken distro to justify such a complaint. Getting 64-bit to work was
a live issue maybe around 2001 or so...
regards, tom lane
On Fri, Jun 27, 2008 at 11:52 AM, Benjamin Weaver <benjamin.weaver@classics.ox.ac.uk> wrote: > Sorry, guys, for wasting bandwidth on this! You guys gave just the answer I > wanted to hear. Sounds like there aren't any problems. > > Not knowing about such things, I was scared by the following quote. Perhaps > binaries do not need to be compiled as 64 bit binaries on a 64 bit machine? Or > perhaps it's way out of date (2004) or simply wrong. Distro support for 64-bit x86 in 2004 was light-years behind where it is now. A lot of stuff was hard to get working back then. Now almost everything basically Just Works. -Doug
On Fri, Jun 27, 2008 at 10:21 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > "Douglas McNaught" <doug@mcnaught.org> writes: >> On Fri, Jun 27, 2008 at 11:52 AM, Benjamin Weaver >> <benjamin.weaver@classics.ox.ac.uk> wrote: >>> Not knowing about such things, I was scared by the following quote. > >> Distro support for 64-bit x86 in 2004 was light-years behind where it >> is now. A lot of stuff was hard to get working back then. Now almost >> everything basically Just Works. > > Even in 2004, the guy would have had to be working on a rather old or > broken distro to justify such a complaint. Getting 64-bit to work was > a live issue maybe around 2001 or so... Yeah, I thought his complaint about pg 64 bit compiling was a bit wacky. I was building 8.0 and 8.1 64 bit on our servers back then and / or installing x86_64 rpms with no problems at all in 2004/5 or so. MySQL compiling on the other hand, has always been a frakking nightmare.
On Thu, 26 Jun 2008, Adam Rich wrote: > Is there any benefit to running a 32-bit OS (rhel 5 in this case) on a > server with more than 4 GB of memory? If you have more than 3GB of memory, you should be using a 64-bit OS. While theoretically the 32-bit code might be smaller which has some advantages, in practice the 64-bit versions will be faster. > For people with experience running postgresql on systems with 16+ GB of > memory, what parameter settings have you found to be effective? (This > would be a large database that's mostly read-only that we'd like to fit > completely in memory) Much larger values for shared_buffers and work_mem seem to be the most effective way to use larger amounts of memory. For example, if you've got 1GB of RAM, it can be hard to allocate >15% of it to shared_buffers while leaving enough enough RAM for OS-level operations, applications, etc. But if you've got 16GB, a large read-only database might usefully set that to 50% of RAM instead. > Is it possible to backup (pg_dump) from a 32-bit OS to a 64-bit OS, > or is a plain SQL dump necessary? pg_dump is a plain SQL dump, it's just a program to make it easier to generate them. You need to do this sort of dump/reload in order to convert from a 32-bit to a 64-bit platform. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD