Re: [PATCH] virtio-blk: allow more than one in-flight request

[Marcelo Tosatti <marcelo@kvack.org>]

On Thu, Mar 27, 2008 at 06:45:14PM +0100, Christian Borntraeger wrote:
> Am Donnerstag, 27. März 2008 schrieb Marcelo Tosatti:
> > 
> > Allow more than one in-flight request in the virtio ring. This allows
> > the host driver to submit requests in parallel.
> [...]
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 3b1a68d..5bb041f 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> [...]
> > @@ -202,7 +204,8 @@ static int virtblk_probe(struct virtio_device *vdev)
> >  		goto out_free_vblk;
> >  	}
> > 
> > -	vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
> > +	vblk->pool = mempool_create_kmalloc_pool(VIRTIO_BLK_POOL_SIZE,
> > +                        sizeof(struct virtblk_req));
> >  	if (!vblk->pool) {
> >  		err = -ENOMEM;
> >  		goto out_free_vq;
> [...]
> 
> Huh? I dont understand. You only change the number of pre-allocated pool 
> entries. mempool_alloc should allow several allocations, even with 1 as 
> initialization value. The pre-initialized value is only for oom situations. 
> No?

Thats right, the mempool allocation will fail under memory pressure
(since __GFP_NOMEMALLOC is passed from mempool_allocate), but under
normal circumstances it will allocate more than one entry.

So ignore the patch. Sorry for the noise.



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