Re: Estimating seq_page_fetch and random_page_fetch - Mailing list pgsql-hackers

From Neil Conway
Subject Re: Estimating seq_page_fetch and random_page_fetch
Date
Msg-id 1173393578.6422.7.camel@localhost.localdomain
Whole thread Raw
In response to Re: Estimating seq_page_fetch and random_page_fetch  (Gregory Stark <stark@enterprisedb.com>)
List pgsql-hackers
On Thu, 2007-03-08 at 17:35 +0000, Gregory Stark wrote:
> When I was running tests I did it on a filesystem where nothing else was
> running. Between tests I unmounted and remounted it. As I understand it Linux
> associates the cache with the filesystem and not the block device and discards
> all pages from cache when the filesystem is unmounted.

On recent Linux kernels, /proc/sys/vm/drop_caches can also be useful:
   http://linux.inet.hr/proc_sys_vm_drop_caches.html

You could also use posix_fadvise() to achieve a similar effect on a per-file
basis.

-Neil




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