Re: Why we are going to have to go DirectIO - Mailing list pgsql-hackers

From Jeff Janes
Subject Re: Why we are going to have to go DirectIO
Date
Msg-id CAMkU=1xu-1g6a7Kv3TmNXieA15sP+t0v4UXzFgkL=QsCged7Kg@mail.gmail.com
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In response to Re: Why we are going to have to go DirectIO  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Why we are going to have to go DirectIO
List pgsql-hackers
On Tuesday, December 10, 2013, Tom Lane wrote:
Jeff Janes <jeff.janes@gmail.com> writes:
> On Tue, Dec 3, 2013 at 11:39 PM, Claudio Freire <klaussfreire@gmail.com>wrote:
>> Problem is, Postgres relies on a working kernel cache for checkpoints.
>> Checkpoint logic would have to be heavily reworked to account for an
>> impaired kernel cache.

> I don't think it would need anything more than a sorted checkpoint.

Nonsense.  We don't have access to the physical-disk-layout information
needed to do reasonable sorting; to say nothing of doing something
intelligent in a multi-spindle environment, or whenever any other I/O
is going on concurrently.

The proposal I was responding to was simply to increase shared_buffers to 80% of RAM *instead of* implementing directIO. 

Cheers,

Jeff

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