----- Original Message ----- From: Jaegeuk Hanse <jaegeuk.hanse@xxxxxxxxx> To: metin d <metdos@xxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx>; "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>; linux-mm@xxxxxxxxx Sent: Friday, November 23, 2012 3:58 AM Subject: Re: Problem in Page Cache Replacement On 11/21/2012 02:25 AM, Jan Kara wrote: > On Tue 20-11-12 09:42:42, metin d wrote: >> 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 Hi Jaegeuk, Yes, it is a tool, you get it from here : http://code.google.com/p/linux-ftools/ Regards, Metin >> >> 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? > >> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href