Hello, Try to install collectd and check the metrics for ram. Best regards, El dia 03/02/2016 2:51 a. m., "John R Pierce" <pierce at hogranch.com> va escriure: > On 2/2/2016 5:34 PM, Benjamin Smith wrote: > >> I'd like to know what the cause of a particular DB server's slowdown >> might be. >> We've ruled out IOPs for the disks (~ 20%) and raw CPU load (top shows >> perhaps >> 1/2 of cores busy, but the system slows to a crawl. >> >> We're suspecting that we're simply running out of memory bandwidth but >> have no >> way to confirm this suspicion. Is there a way to test for this? Think: >> iostat >> but for memory bandwidth instead of disk IO. >> > > memory bandwidth would show up as CPU busy, there's no distinction. > > 50% of your cores 100% busy, how many cores and how many waiting database > tasks are there? typically with most database servers, one user connection > == one core at a time. so if you have 16 cores, and only 8 busy/active > database connections, that will tie up those 8 cores and leave the other 8 > free. now the 8 processes will probably get bounced around between the > cores, so it could end up looking like all 16 cores are 50% busy averaged > over some sample rate, but thats the same net difference.. > > > > -- > john r pierce, recycling bits in santa cruz > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > https://lists.centos.org/mailman/listinfo/centos >