Scott, regardless of operating system support for DMA, an application
may not benefit from it if it doesn't use appropriate system calls.
PostgreSQL is implemented mostly in C, so I do not know whether it
needs to use special procedure calls, however this is true, for
example, for Java
http://www.ibm.com/developerworks/library/j-zerocopy/
2011/9/9 Scott Marlowe <scott.marlowe@gmail.com>:
> On Fri, Sep 9, 2011 at 11:55 AM, Antonio Rodriges <antonio.rrz@gmail.com> wrote:
>> Hello,
>>
>> Does anyone know whether PostgreSQL uses DMA (Direct Memory Access) in
>> certain cases to improve networking IO performance?
>>
>> I mean "simple" query is which doesn't require any CPU processing, for ex
>> SELECT column_a FROM table_b WHERE date = "2001-10-05"
>>
>> I need this to devise the best logic for the system with PostgreSQL as
>> a layer. Certainly I could study PostgreSQL sources or test it with a
>> simple application but I hope PostgreSQL experts are aware of this
>> feature.
>
> That's all up to your hardware and OS, not postgresql
>
--
Kind regards,
Antonio Rodriges