Magnus Hagander wrote:
On Tue, Feb 9, 2010 at 09:53, David Kerr <dmk@xxxxxxxxxxxxxx> wrote:
Guillaume Lelarge wrote:
Le 09/02/2010 09:35, David Kerr a écrit :
Guillaume Lelarge wrote:
Le 09/02/2010 05:49, John R Pierce a écrit :
David Kerr wrote:
maintenance_work_mem = 1GB
So evidently, when it tries to actually allocate 1GB, it can't do it.
Ergo, that setting is too high for your machine.
...
seems like i've got 2GB free.
is this a 64bit postgres build?
if not, you're probably running out of virtual address space in the 32
bit user space, which is limited to like 2gb.
IIRC, the virtual address space in 32bit platforms is 4GB.
IIRC, on Linux that will be a max of 3Gb available to userspace
processes. Certainly not 4Gb - but it could be 2.
it is a 32bit box.
the other possibility, and here I'm not sure, is that
maintenance_work_mem is coming out of shared memory, and if so, you've
exceeeded your SHMMAX kernel limit.
work_mem and maintenance_work_mem are not shared memory. AFAICT, David
need to check if the VACUUM works with a lower setting for
maintenance_work_mem. For example, 512MB could work.
Yes, vacuum -z works with 512MB. so any idea what was causing it not to
work with 1GB?
Tom already explained that. The process couldn't get the 1GB it was
allowed to use with this setting of maintenance_work_mem.
Well, that made sense until I freed up a lot of memory on the box. I had
tried it again with 2GB of free memory available to me to use. My ulimits
are all unlimited. So i'm wondering if there's a kernel setting I need, or
something similar.
You may well be running out of *address space* rather than pure
memory. PostgreSQL is failing to allocate 1Gb of *continuous* memory.
Not just 1Gb of memory anywhere. Shared memory, for example, lives at
a fixed location already. There may be >1Gb free in the address space,
just not where you need it.
Ok that makes sense, it never occurred to me that malloc would require
a contiguous chunk the full size of the allocation request.
In general, when you are starting to talk about things like 1Gb
maintenance_work_mem, you should've switched to 64-bit a while ago :-)
Yes, I know, I actually specced out the server as 64 bit but someone
messed up and i'm making due with what I have.
oh, hmm, my swap is 517Megs, that probably isn't helping. Usually swap is
1.5/2x available memory, isn't it? (it is for most unix's and oracle, but
i'm not sure about PG and linux)
I don't think that affects this problem.
ok.
Thanks
Dave
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