Hi Scott,
Thanks for the reply.
Top is showing 10157008 / 15897160 in kernel cache, so postgres is using 37% right now, following what you are saying. I realize the load isn't peaking right now, but wouldn't it be nice to have some of the indexes cached in memory?
In your case 1868064 / 2000000 or 7 % of your memory is being used by postgres. That sort of proves my point. Shouldn't postgres use more than 7% of the memory. Doesn't that seem like 93% isn't being used?
~DjK
top - 08:59:38 up 277 days, 23:03, 1 user, load average: 0.63, 0.51, 0.40Tasks: 101 total, 1 running, 100 sleeping, 0 stopped, 0 zombieCpu0 : 0.0% us, 1.0% sy, 0.0% ni, 99.0% id, 0.0% wa, 0.0% hi, 0.0% siCpu1 : 0.0% us, 0.0% sy, 0.0% ni, 99.7% id, 0.3% wa, 0.0% hi, 0.0% siCpu2 : 0.7% us, 0.7% sy, 0.0% ni, 98.3% id, 0.0% wa, 0.0% hi, 0.3% siCpu3 : 0.0% us, 0.0% sy, 0.0% ni, 99.3% id, 0.7% wa, 0.0% hi, 0.0% siMem: 15897160k total, 10477104k used, 5420056k free, 169780k buffersSwap: 16779768k total, 78912k used, 16700856k free, 10157008k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1975 postgres 15 0 33412 7932 1388 S 1.0 0.0 1211:09 postgres: stats collector process 1971 postgres 15 0 1085m 14m 14m S 0.3 0.1 2323:28 /postgres 1 root 16 0 640 80 48 S 0.0 0.0 0:11.55 init [3] 2 root RT 0 0 0 0 S 0.0 0.0 0:02.30 [migration/0] 3 root 34 19 0 0 0 S 0.0 0.0 0:06.99 [ksoftirqd/0] 4 root RT 0 0 0 0 S 0.0 0.0 0:00.82 [migration/1] 5 root 34 19 0 0 0 S 0.0 0.0 0:56.60 [ksoftirqd/1] 6 root RT 0 0 0 0 S 0.0 0.0 0:10.71 [migration/2] 7 root 34 19 0 0 0
> Date: Wed, 14 Nov 2007 15:20:53 -0600> From: scott(dot)marlowe(at)gmail(dot)com> To: bitsandbytes88(at)hotmail(dot)com> Subject: Re: [ADMIN] cached memory> CC: pgsql-admin(at)postgresql(dot)org> > On Nov 14, 2007 3:13 PM, dx k9 <bitsandbytes88(at)hotmail(dot)com> wrote:> >> > In looking at some cacti memory usage graphs, the Oracle servers show> > only 6 of a total of16 GB of RAM as 'Total Available'. Whereas, our> > Postgres version 8.24 servers show all 16 GB of RAM totally available or> > free. Some people are asking why Postgres doesn't take that memory and> > lock into it, so you can't see less 'total available' memory. We use a lot> > of B-tree indexes. This may or may not be related, but it there a good way> > to make sure those stay in memory?> > Not sure what you mean by totally available. Is the OS using it to> cache? If so, why should postgresql do what the OS already does so> well.> > Oracle was written back when OSes were barely more than program> loaders and it had to do everything, from having its own file systems> to buffering / caching to memory management to job schedulers.> > PostgreSQL was written as Unix was maturing (mostly) and takes> advantage of all the cool things a modern unix comes with, and one of> those things is kernel level caching of disk files.> > So, what does free / top have to say about your memory? And how hard> have these servers been working. For instance, my RHEL4 reporting> server, with only 2 Gigs in it shows 1868064 used as kernel cache.> The rest is mostly pgsql processes
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