Re: auto-sizing wal_buffers

On Sun, Jan 16, 2011 at 1:52 AM, Greg Smith <greg@2ndquadrant.com> wrote:
> Fujii Masao wrote:
>>
>> +int                    XLOGbuffersMin = 8;
>>
>> XLOGbuffersMin is a fixed value. I think that defining it as a macro
>> rather than a variable seems better.
>>
>> +               if (XLOGbuffers > 2048)
>> +                       XLOGbuffers = 2048;
>>
>> Using "XLOG_SEG_SIZE/XLOG_BLCKSZ" rather than 2048 seems
>> better.
>>
>> +#wal_buffers = -1                      # min 32kB, -1 sets based on
>> shared_buffers
>>
>> Typo: s/32kB/64kB
>>
>
> Thanks, I've fixed all these issues and attached a new full patch, pushed to
> github, etc.  Tests give same results back, and it's nice that it scale to
> reasonable behavior if someone changes their XLOG segment size.

Thanks for the update.

+/* Minimum setting used for a lower bound on wal_buffers */
+#define XLOG_BUFFER_MIN            4

Why didn't you use XLOG_BUFFER_MIN instead of XLOGbuffersMin?
XLOG_BUFFER_MIN is not used anywhere for now.

+        if (XLOGbuffers < (XLOGbuffersMin * 2))
+            XLOGbuffers = XLOGbuffersMin * 2;
+        }

Why is the minimum value 64kB only when wal_buffers is set to
-1? This seems confusing for users.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center