On Tue, 9 Apr 2013, Tejun Heo wrote:
> On Tue, Apr 09, 2013 at 01:51:43PM -0400, Mikulas Patocka wrote:
> > The patch dm-crypt-sort-requests.patch sorts write requests submitted by a
> > single thread. The requests are sorted according to the sector number,
> > rb-tree is used for efficient sorting.
>
> Hmmm? Why not just keep the issuing order along with plugging
> boundaries?
What do you mean?
I used to have a patch that keeps order of requests as they were
introduced, but sorting the requests according to sector number is a bit
simpler.
> > So it seems that CFQ has some deficiency that it cannot merge adjacent
> > requests done by different processes.
>
> As I wrote before, please use bio_associate_current(). Currently,
> dm-crypt is completely messing up all the context information that cfq
> depends on to schedule IOs. Of course, it doesn't perform well.
bio_associate_current() is only valid on a system with cgroups and there
are no cgroups on the kernel where I tested it. It is an empty function:
static inline int bio_associate_current(struct bio *bio) { return -ENOENT; }
Mikulas
> Thanks.
>
> --
> tejun
>
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