Re: WAL prefetch

On 06/15/2018 08:01 PM, Andres Freund wrote:
> On 2018-06-14 10:13:44 +0300, Konstantin Knizhnik wrote:
>>
>>
>> On 14.06.2018 09:52, Thomas Munro wrote:
>>> On Thu, Jun 14, 2018 at 1:09 AM, Konstantin Knizhnik
>>> <k.knizhnik@postgrespro.ru> wrote:
>>>> pg_wal_prefetch function will infinitely traverse WAL and prefetch block
>>>> references in WAL records
>>>> using posix_fadvise(WILLNEED) system call.
>>> Hi Konstantin,
>>>
>>> Why stop at the page cache...  what about shared buffers?
>>>
>>
>> It is good question. I thought a lot about prefetching directly to shared
>> buffers.
> 
> I think that's definitely how this should work.  I'm pretty strongly
> opposed to a prefetching implementation that doesn't read into s_b.
> 

Could you elaborate why prefetching into s_b is so much better (I'm sure 
it has advantages, but I suppose prefetching into page cache would be 
much easier to implement).

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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