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Re: EXPLAIN ANALYZE printing logical and hardware I/O per-node

From: Decibel! <decibel(at)decibel(dot)org>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: "Neil Conway" <neilc(at)samurai(dot)com>, "pgsql-hackers list" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: EXPLAIN ANALYZE printing logical and hardware I/O per-node
Date: 2007-12-19 01:17:53
Message-ID: 43DDC985-FC7C-4DA2-A576-9CDB0C63FAFF@decibel.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Dec 18, 2007, at 3:32 AM, Gregory Stark wrote:
>> Also, has anyone looked into adding a class of system calls that   
>> would
>> actually tell us if the kernel issued physical IO? I find it  hard  
>> to believe
>> that other RDBMSes wouldn't like to have that info...
>
> Yeah, I think that's called "DTrace"


That seems like way overkill...

When a read() call returns, surely the kernel knows whether it  
actually issued a physical read request to satisfy that. I don't see  
any reason why you couldn't have a version of read() that returns  
that information. I also rather doubt that we're the only userland  
software that would make use of that.
-- 
Decibel!, aka Jim C. Nasby, Database Architect  decibel(at)decibel(dot)org
Give your computer some brain candy! www.distributed.net Team #1828


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