On Mon, 2009-09-28 at 10:36 -0700, Josh Berkus wrote:
On 9/26/09 8:19 AM, Greg Smith wrote:
This means that the question you want an answer to is if the OS cache
isn't really available, where does giving memory to shared_buffers
becomes less efficient than not caching things at all? My
On 9/26/09 8:19 AM, Greg Smith wrote:
This means that the question you want an answer to is if the OS cache
isn't really available, where does giving memory to shared_buffers
becomes less efficient than not caching things at all? My guess is
that this number is much larger than 10GB, but I
On Thu, 24 Sep 2009, Dan Sugalski wrote:
Is there any practical limit to the number of shared buffers PG 8.3.7 can
handle before more becomes counter-productive?
There are actually two distinct questions here you should consider,
because the popular wisdom here and what makes sense for your
Is there any practical limit to the number of shared buffers PG 8.3.7
can handle before more becomes counter-productive?
It is more efficient to have the page in shared buffers, rather than doing
a context switch to the OS, copying the entire page from the OS's cache
into shared buffers,
On Fri, 25 Sep 2009, Jeff Janes wrote:
Does it do this even if the block was already in shared_buffers?
Usually not. The buffer ring algorithm is used to manage pages that are
read in specifically to satisfy a sequential scan (there's a slightly
different ring method used for VACUUM too).
On Sat, Sep 26, 2009 at 9:57 AM, Gerhard Wiesinger li...@wiesinger.com wrote:
On Sat, 26 Sep 2009, Greg Smith wrote:
On Fri, 25 Sep 2009, Jeff Janes wrote:
Does it do this even if the block was already in shared_buffers?
Usually not. The buffer ring algorithm is used to manage pages that
On Sat, Sep 26, 2009 at 8:19 AM, Greg Smith gsm...@gregsmith.com wrote:
Another problem spot are checkpoints. If you dirty a very large buffer
cache, that whole thing will have to get dumped to disk eventually, and on
some workloads people have found they have to reduce shared_buffers
On Sat, 26 Sep 2009, Jeff Janes wrote:
On Sat, Sep 26, 2009 at 8:19 AM, Greg Smith gsm...@gregsmith.com wrote:
Another problem spot are checkpoints. If you dirty a very large buffer
cache, that whole thing will have to get dumped to disk eventually, and on
some workloads people have found
At 12:36 AM -0400 9/25/09, Tom Lane wrote:
Dan Sugalski d...@sidhe.org writes:
Is there any practical limit to the number of shared buffers PG 8.3.7
can handle before more becomes counter-productive?
Probably, but I've not heard any definitive measurements showing an
upper limit. The
* Dan Sugalski d...@sidhe.org [090925 06:06]:
I'll have to go check, but I think it does. This box hasn't actually hit
swap since it started -- a good chunk of that RAM is used as
semi-permanent disk cache but unfortunately the regular day-to-day use of
this box (they won't let me have
[ai...@highrise.ca]
Sent: Friday, September 25, 2009 6:33 AM
To: Dan Sugalski
Cc: Tom Lane; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] PG 8.3 and large shared buffer settings
* Dan Sugalski d...@sidhe.org [090925 06:06]:
I'll have to go check, but I think it does. This box hasn't
* Scott Carey sc...@richrelevance.com [090925 11:57]:
That won't work well anyway because the postgres shared_buffers dos not cache
things that are sequentially scanned (it uses a ring buffer for each scan).
So, for any data that is only accessed by sequential scan, you're relying on
the
On Fri, Sep 25, 2009 at 8:53 AM, Scott Carey sc...@richrelevance.com wrote:
That won't work well anyway because the postgres shared_buffers dos not cache
things that are sequentially scanned (it uses a ring buffer for each scan).
So, for
any data that is only accessed by sequential scan,
Is there any practical limit to the number of shared buffers PG 8.3.7
can handle before more becomes counter-productive? I remember the
buffer management algorithm used to get unhappy with too many buffers
and past a certain point performance dropped with extra memory
pitched at Postgres.
My
Dan Sugalski d...@sidhe.org writes:
Is there any practical limit to the number of shared buffers PG 8.3.7
can handle before more becomes counter-productive?
Probably, but I've not heard any definitive measurements showing an
upper limit. The traditional wisdom of limiting it to 1G or so dates
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