On 11/21/2012 02:25 AM, Jan Kara wrote:

On Tue 20-11-12 09:42:42, metin d wrote:

quoted

I have two PostgreSQL databases named data-1 and data-2 that sit on the
same machine. Both databases keep 40 GB of data, and the total memory
available on the machine is 68GB.

I started data-1 and data-2, and ran several queries to go over all their
data. Then, I shut down data-1 and kept issuing queries against data-2.
For some reason, the OS still holds on to large parts of data-1's pages
in its page cache, and reserves about 35 GB of RAM to data-2's files. As
a result, my queries on data-2 keep hitting disk.

I'm checking page cache usage with fincore. When I run a table scan query
against data-2, I see that data-2's pages get evicted and put back into
the cache in a round-robin manner. Nothing happens to data-1's pages,
although they haven't been touched for days.

Hi metin d,

fincore is a tool or ...? How could I get it?

Regards,
Jaegeuk

quoted

Does anybody know why data-1's pages aren't evicted from the page cache?
I'm open to all kind of suggestions you think it might relate to problem.

   Curious. Added linux-mm list to CC to catch more attention. If you run
echo 1 >/proc/sys/vm/drop_caches
   does it evict data-1 pages from memory?

quoted

This is an EC2 m2.4xlarge instance on Amazon with 68 GB of RAM and no
swap space. The kernel version is:

$ uname -r
3.2.28-45.62.amzn1.x86_64
Edit:

and it seems that I use one NUMA instance, if  you think that it can a problem.

$ numactl --hardware
available: 1 nodes (0)
node 0 cpus: 0 1 2 3 4 5 6 7
node 0 size: 70007 MB
node 0 free: 360 MB
node distances:
node   0
   0:  10

								Honza

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