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Date: Wed, 5 Nov 2003 18:54:04 +0300 (MSK)
From: Igor Sysoev <is@rambler-co.ru>
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On Wed, 5 Nov 2003, Robert Watson wrote:

> On Wed, 5 Nov 2003, Igor Sysoev wrote:
> 
> > As to worker kthreads I think it's better to queue aio operation as it
> > was made in src/sys/kern/vfs_aio.c:aio_qphysio(). 
> 
> One of the things that worries me about the proposal to use kernel worker
> threads to perform the I/O is that this can place a fairly low upper bound
> on effective parallelism, unless the kernel threads themselves can issue
> the I/O's asynchronously.  In the network stack itself, we are event and
> queue driven without blocking--if we can maintain the apparent semantics
> to the application, it would be very nice to be able to handle that at the
> socket layer itself.  I.e., not waste a thread + stack per "in-progress" 
> operation, and instead have a worker or two that simply propel operations
> up and down the stack (similar to geom_up and geom_down). 

As far as I understand src/sys/kern/vfs_aio.c:aio_qphysio() (that handles
AIO on raw disks) does not use kthreads and simply queues operations.


Igor Sysoev
http://sysoev.ru/en/