On Fri, Aug 14, 2009 at 12:00 PM, Jeremy Carroll<jeremy.carroll@xxxxxxxxxxxxxxxxxxxxx> wrote: > I am confused about what the OS is reporting for memory usage on CentOS 5.3 > Linux. Looking at the resident memory size of the processes. Looking at the > resident size of all postgres processes, the system should be using around > 30Gb of physical ram. I know that it states that it is using a lot of shared > memory. My question is how to I determine how much physical RAM postgres is > using at any point in time? OK, take the first pg process, and write down its RES size. For all the rest, write down RES-SHR for how much more it's using. Since they use a lot of shared memory, and since you're showing something like 7.9G shared, I'm gonna guess that's the size of your shared_buffers. With those numbers you should get something just over a shade of 7.9G used, and most of that is shared_buffers. Also, a quick check is to look at this number: 22825616k cached which tells you how much memory the OS is using for cache, which is ~22G. I note that you've got 2G swapped out, this might well be shared_buffers or something you'd rather not have swapped out. Look into setting your swappiness lower (5 or so should do) to stop the OS from swapping so much out. /sbin/sysctl -a|grep swappiness vm.swappiness = 60 is the default. You can change it permanently by editing your /etc/sysctl.conf file (or wherever it lives) and rebooting, or running /sbin/sysctl -p to process the entries and make them stick this session. My big servers run with swappiness of 1 with no problems. > > This server has 24Gb of ram, and is reporting that 23GB is free for use. See > calculation below > > (Memory Total – Used) + (Buffers + Cached) = Free Memory > (24675740 – 24105052) + (140312 + 22825616) = 23,536,616 or ~23 Gigabytes > > > So if my server has 23Gb of ram that is free for use, why is postgres > reporting resident sizes of 30GB? Shared memory is reporting the same > values, so how is the OS reporting that only 1Gb of RAM is being used? > > Help? > > top - 12:43:41 up 2 days, 19:04, 2 users, load average: 4.99, 4.81, 4.33 > Tasks: 245 total, 4 running, 241 sleeping, 0 stopped, 0 zombie > Cpu(s): 26.0%us, 0.0%sy, 0.0%ni, 73.9%id, 0.1%wa, 0.0%hi, 0.0%si, > 0.0%st > Mem: 24675740k total, 24105052k used, 570688k free, 140312k buffers > Swap: 2097144k total, 272k used, 2096872k free, 22825616k cached > --------------------- > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 19469 postgres 15 0 8324m 7.9g 7.9g S 0.0 33.7 0:54.30 postgres: > writer process > 29763 postgres 25 0 8329m 4.5g 4.5g R 99.8 19.0 24:53.02 postgres: > niadmin database x.x.x.49(51136) UPDATE > 29765 postgres 25 0 8329m 4.4g 4.4g R 99.8 18.8 24:42.77 postgres: > niadmin database x.x.x.49(51138) UPDATE > 31778 postgres 25 0 8329m 4.2g 4.2g R 99.5 17.8 17:56.95 postgres: > niadmin database x.x.x.49(51288) UPDATE > 31779 postgres 25 0 8329m 4.2g 4.2g R 99.1 17.8 17:59.62 postgres: > niadmin database x.x.x.49(51289) UPDATE > 31780 postgres 23 0 8329m 4.1g 4.1g R 100.1 17.5 17:52.53 postgres: > niadmin database x.x.x.49(51290) UPDATE > 19467 postgres 15 0 8320m 160m 160m S 0.0 0.7 0:00.24 > /opt/PostgreSQL/8.3/bin/postgres -D /opt/PostgreSQL/8.3/data > > 19470 postgres 15 0 8324m 2392 1880 S 0.0 0.0 0:01.72 postgres: wal > writer process -- When fascism comes to America, it will be intolerance sold as diversity. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
