Re: Allow a per-tablespace effective_io_concurrency setting

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On 02/09/2015 15:53, Andres Freund wrote:
> On 2015-07-18 12:17:39 +0200, Julien Rouhaud wrote:
>
> You also didn't touch /* * How many buffers PrefetchBuffer callers
> should try to stay ahead of their * ReadBuffer calls by. This is
> maintained by the assign hook for * effective_io_concurrency. Zero
> means "never prefetch". */ int target_prefetch_pages = 0; which
> surely doesn't make sense anymore after these changes.
>
> But do we even need that variable now?
>

I thought this was related to the effective_io_concurrency GUC
(possibly overloaded by the per-tablespace setting), so I didn't make
any change on that.

I also just found an issue with my previous patch, the global
effective_io_concurrency GUC was ignored if the tablespace had a
specific seq_page_cost or random_page_cost setting, I just fixed that
in my local branch.

>> diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
>> index dc167f9..57008fc 100644 --- a/src/include/utils/guc.h +++
>> b/src/include/utils/guc.h @@ -26,6 +26,9 @@ #define MAX_KILOBYTES
>> (INT_MAX / 1024) #endif
>>
>> +/* upper limit for effective_io_concurrency */ +#define
>> MAX_IO_CONCURRENCY 1000 + /* * Automatic configuration file name
>> for ALTER SYSTEM. * This file will be used to store values of
>> configuration parameters @@ -256,6 +259,8 @@ extern int
>> temp_file_limit;
>>
>> extern int num_temp_buffers;
>>
>> +extern int effective_io_concurrency; +
>
> target_prefetch_pages is declared in bufmgr.h - that seems like a
> better place for these.
>

I was rather sceptical about that too. I'll move these in bufmgr.h.

Regards.

- --
Julien Rouhaud
http://dalibo.com - http://dalibo.org
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