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.fujii@gmail.com>  wrote:
>> On Fri, Sep 16, 2011 at 7:53 AM, Simon Riggs<simon@2ndquadrant.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.

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