Re: hugepage configuration for V.9.4.0

[Scott Whitney <scott@xxxxxxxxxxx>]

Usually I tweak the kernel shmmax, shmmni and shmall values in /proc/sys.

4GB _might_ be too small, in fact, but tweaking those parameters ought to get you started at least.

http://www.postgresql.org/docs/9.0/static/kernel-resources.html

----- On Jan 29, 2015, at 11:54 AM, John Scalia <jayknowsunix@xxxxxxxxx> wrote:

I'm certain that I'm no expert for this one, as I've never had to configure this parameter for anything prior, but I continue to get a startup error when I try to use this. The
server is a VM running CentOS 6.5 with 4 Gb allocated to it. When I started setting "huge_pages = on", the server reported:

%FATAL: could not map anonymous shared memory: Cannot allocate memory
%HINT: this error usually means that PostgreSQL's request for a shared memory segment exceeded available memory, swap space, or huge pages. To reduce the request size (currently
1124876288 bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections.

Further research showed that server's /sys/kernel/mm/transparent_hugepage/enabled file contained "[always] madvise never"

As I was concerned about the "always" setting, I used "cat madvise > " to the file so it reported "always [madvise] never" I even set this in /etc/rc.local and performed a reboot.

Regardless of which setting, however, I receive the same failure message. Per its suggestions, my settings are shared_buffers = 1024Mb and max_connections = 100.

Should I reduce these values? Is a 4 Gb test server too small to use huge_pages? The server does run just fine with "huge_pages = try" or "off". What else should I be checking?
--
Jay




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