Re: [Qemu-devel] [RFC PATCH 2/3] raw-posix: Convert Linux AIO submission to coroutines

[Markus Armbruster]

Ming Lei <address@hidden> writes:

> Hi Kevin,
>
> On Wed, Nov 26, 2014 at 10:46 PM, Kevin Wolf <address@hidden> wrote:
>> This improves the performance of requests because an ACB doesn't need to
>> be allocated on the heap any more. It also makes the code nicer and
>> smaller.
>
> I am not sure it is good way for linux aio optimization:
>
> - for raw image with some constraint, coroutine can be avoided since
> io_submit() won't sleep most of times
>
> - handling one time coroutine takes much time than handling malloc,
> memset and free on small buffer, following the test data:
>
>          --   241ns per coroutine

What do you mean by "coroutine" here?  Create + destroy?  Yield?

>          --   61ns per (malloc, memset, free for 128bytes)
>
> I still think we should figure out a fast path to avoid cocourinte
> for linux-aio with raw image, otherwise it can't scale well for high
> IOPS device.
>
> Also we can use simple buf pool to avoid the dynamic allocation
> easily, can't we?
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