[Drbd-dev] [PATCH v4 01/11] block: make generic_make_request handle arbitrarily sized bios

[Ming Lin]

On Wed, May 27, 2015 at 5:36 PM, Alasdair G Kergon <agk at redhat.com> wrote:
> On Wed, May 27, 2015 at 04:42:44PM -0700, Ming Lin wrote:
>> Here are fio results of XFS on a DM stripped target with 2 SSDs + 1 HDD.
>> Does it make sense?
>
> To stripe across devices with different characteristics?
>
> Some suggestions.
>
> Prepare 3 kernels.
>   O - Old kernel.
>   M - Old kernel with merge_bvec_fn disabled.

How to disable it?
Maybe just hack it as below?

void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
{
        //q->merge_bvec_fn = mbfn;
}

>   N - New kernel.