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DateSun, 17 Oct 2004 08:25:33 +0200
FromAvi Kivity <>
SubjectRe: [PATCH 1/2] aio: add vectored I/O support
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.

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