Re: [PERFORM] shared_buffer optimization
On Tue, Aug 08, 2006 at 08:20:01AM -0400, Christopher Browne wrote: I'm not aware of any actual evidence having emerged that it is of any value to set shared buffers higher than 1. http://flightaware.com They saw a large increase in how many concurrent connections they could handle when they bumped shared_buffers up from ~10% to 50% of memory. Back then they had 4G of memory. They're up to 12G right now, but haven't bumped shared_buffers up. Every single piece of advice I've seen on shared_buffers comes from the 7.x era, when our buffer management was extremely simplistic. IMO all of that knowledge was made obsolete when 8.0 came out, and our handling of shared_buffers has improved ever further since then. This is definately an area that could use a lot more testing. -- Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] Pervasive Software http://pervasive.comwork: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---(end of broadcast)--- TIP 4: Have you searched our list archives? http://archives.postgresql.org
Re: [PERFORM] shared_buffer optimization
Jim C. Nasby [EMAIL PROTECTED] writes: Every single piece of advice I've seen on shared_buffers comes from the 7.x era, when our buffer management was extremely simplistic. IMO all of that knowledge was made obsolete when 8.0 came out, and our handling of shared_buffers has improved ever further since then. This is definately an area that could use a lot more testing. Actually I think it was probably 8.1 that made the significant difference there, by getting rid of the single point of contention for shared-buffer management. I concur that 7.x-era rules of thumb may well be obsolete --- we need some credible scaling tests ... regards, tom lane ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
Re: [PERFORM] shared_buffer optimization
Quoth [EMAIL PROTECTED] (Ruben Rubio): Hi, I have a question with shared_buffer. Ok, I have a server with 4GB of RAM - # cat /proc/meminfo MemTotal: 4086484 kB [...] - So, if I want to, for example, shared_buffer to take 3 GB of RAM then shared_buffer would be 393216 (3 * 1024 * 1024 / 8) Postmaster dont start. Error: FATAL: shmat(id=360448) failed: Invalid argument I can set a less value, but not higher than 3 GB. Am I doing something wrong? Any idea? Yes, you're trying to set the value way too high. The rule of thumb is to set shared buffers to the lesser of 1 and 15% of system memory. In your case, that would be the lesser of 1 and 78643, which is 1. I'm not aware of any actual evidence having emerged that it is of any value to set shared buffers higher than 1. -- let name=cbbrowne and tld=acm.org in name ^ @ ^ tld;; http://linuxdatabases.info/info/x.html Rules of the Evil Overlord #25. No matter how well it would perform, I will never construct any sort of machinery which is completely indestructible except for one small and virtually inaccessible vulnerable spot. http://www.eviloverlord.com/ ---(end of broadcast)--- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
