Re: Separating bgwriter and checkpointer

On 20.09.2011 10:48, Simon Riggs wrote:
> On Fri, Sep 16, 2011 at 2:38 AM, Fujii Masao<masao(dot)fujii(at)gmail(dot)com> wrote:
>> On Fri, Sep 16, 2011 at 7:53 AM, Simon Riggs<simon(at)2ndquadrant(dot)com> wrote:
>>> This patch splits bgwriter into 2 processes: checkpointer and
>>> bgwriter, seeking to avoid contentious changes. Additional changes are
>>> expected in this release to build upon these changes for both new
>>> processes, though this patch stands on its own as both a performance
>>> vehicle and in some ways a refcatoring to simplify the code.
>>
>> I like this idea to simplify the code. How much performance gain can we
>> expect by this patch?
>
> On heavily I/O bound systems, this is likely to make a noticeable
> difference, since bgwriter reduces I/O in user processes.

Hmm. If the system is I/O bound, it doesn't matter which process
performs the I/O. It's still the same amount of I/O in total, and in an
I/O bound system, that's what determines the overall throughput.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com