Re: Separating bgwriter and checkpointer

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.

The overhead of sending signals between processes is much less than I
had previously thought, so I expect no problems there, even on highly
loaded systems.

>> Current patch has a bug at shutdown I've not located yet, but seems
>> likely is a simple error. That is mainly because for personal reasons
>> I've not been able to work on the patch recently. I expect to be able
>> to fix that later in the CF.
>
> You seem to have forgotten to include checkpointor.c and .h in the patch.

I confirm this error. I'll repost full patch later in the week when I
have more time.

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