Re: [PATCH 1/2] aio: add vectored I/O support

[Avi Kivity]

Joel Becker wrote:

> > I think what happened was that the number of iocbs submitted (64 iocbs 
> > of 4K each) did not merge because the device queue depth was very large; 
> > no queuing occured because (I imagine) merging happens while a request 
> > is waiting for disk readiness.
> >    
>
> 	Why did you submit 64 iocbs of 4K?  Was every page virtually
> discontiguous, or did you arbitrarily decide to create a worst-case?
>  
The application (a userspace filesystem with its own cache) manages 
memory in 4K pages, but can perform much larger I/Os, for example during 
readahead and after merging writes. After a very short while memory is 
completely fragmented.


--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/