|Subject||Re: [firebird-support] large system slows over time|
there is a significant time in iowait and this is a VM, so a disk contention issue at the hyper-visor level ?
Nick Upson, Telensa Ltd, Senior Operations Network Engineer
direct +44 (0) 1799 533252, support hotline +44 (0) 1799 399200
On 8 May 2015 at 14:55, Steve Wiser steve@... [firebird-support] <email@example.com> wrote:-steveWhat I would be interested in seeing is that when you run your gbak backup go ahead and also run top. Are you seeing a lot of CPU time being spent in IOWait? If so that would mean that the CPU is being starved of data and is waiting around -- usually because the disk isn't fast enough. We normally only see this on virtual hosts though.Hi Nick,My interpretation of those stats is that you are now out of memory as I always look at the Swap Used. You aren't using any. My experience with Linux is that the OS will take as much memory as it can/needs so it can look like you are maxed out on RAM usage or something, but you really need to pay attention to the swap used.On Fri, May 8, 2015 at 6:32 AM, Nick Upson nu@... [firebird-support] <firstname.lastname@example.org> wrote:Your mention of memory & paging got me thinking. I expected the output below to show the memory was fully used such that more RAM would helpbut unless I'm reading this wrong only 5.3Gb is being used and 2.4 GB is unused so more RAM will be no help, can anyone confirm or put me right$ cat /proc/meminfoMemTotal: 8309036 kBMemFree: 307408 kBBuffers: 59296 kBCached: 7433812 kBSwapCached: 32 kBActive: 5365212 kBInactive: 2470416 kBHighTotal: 7471040 kBHighFree: 18724 kBLowTotal: 837996 kBLowFree: 288684 kBSwapTotal: 4095992 kBSwapFree: 4095788 kBDirty: 186968 kBWriteback: 0 kBAnonPages: 342384 kBMapped: 140812 kBSlab: 148064 kBPageTables: 6824 kBNFS_Unstable: 0 kBBounce: 0 kBCommitLimit: 8250508 kBCommitted_AS: 2795520 kBVmallocTotal: 116728 kBVmallocUsed: 5788 kBVmallocChunk: 110588 kBHugePages_Total: 0HugePages_Free: 0HugePages_Rsvd: 0Hugepagesize: 2048 kBOn 5 May 2015 at 15:21, Ann Harrison aharrison@... [firebird-support] <email@example.com> wrote:
Hi Nick,...I have a system that is slowing down the longer it stays running and I'd like to know why.Is there any evidence I can gather before I reboot the system which I expect (from past experience) will return the system to the better performanceHmmm.... If rebooting will solve the problem and you don't have a very long running transaction, then I doubt that garbage accumulation or collection is the source of the problem.Nor is there anything else wrong with your physical database - fragmentation or whatever.I'd look at memory usage - using both Firebird and OS tools. Look for paging before you reboot.After you reboot, track memory usage daily or more often. It doesn't take much of a leak - or unfortunate caching - to built up over month of 27 tps.Accelerating the move to 2.5.4 would also be a good idea, both because it may correct the problem and because it probably offers better diagnostic tools for this sort of problem.Good luck,Ann