diff mbox series

[rdma-next,v1,2/3] RDMA/rw: Support threshold for registration vs scattering to local pages

Message ID 20191007115819.9211-3-leon@kernel.org
State Not Applicable
Delegated to: David Miller
Headers show
Series Optimize SGL registration | expand

Commit Message

Leon Romanovsky Oct. 7, 2019, 11:58 a.m. UTC 
From: Yamin Friedman <yaminf@mellanox.com>

If there are more scatter entries than the recommended limit provided by
the ib device, UMR registration is used. This will provide optimal
performance when performing large RDMA READs over devices that advertise
the threshold capability.

With ConnectX-5 running NVMeoF RDMA with FIO single QP 128KB writes:
Without use of cap: 70Gb/sec
With use of cap: 84Gb/sec

Signed-off-by: Yamin Friedman <yaminf@mellanox.com>
Reviewed-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
---
 drivers/infiniband/core/rw.c | 14 ++++++++------
 include/rdma/ib_verbs.h      |  2 ++
 2 files changed, 10 insertions(+), 6 deletions(-)

--
2.20.1

Comments

Christoph Hellwig Oct. 7, 2019, 12:12 p.m. UTC | #1 
Sorry for nitpicking again, but..

On Mon, Oct 07, 2019 at 02:58:18PM +0300, Leon Romanovsky wrote:
> @@ -37,15 +39,15 @@ static inline bool rdma_rw_can_use_mr(struct ib_device *dev, u8 port_num)
>   * Check if the device will use memory registration for this RW operation.
>   * We currently always use memory registrations for iWarp RDMA READs, and
>   * have a debug option to force usage of MRs.
> - *
> - * XXX: In the future we can hopefully fine tune this based on HCA driver
> - * input.

The above comment needs an updated a la:

 * Check if the device will use memory registration for this RW operation.
 * For RDMA READs we must use MRs on iWarp and can optionaly use them as an
 * optimaztion otherwise.  Additionally we have a debug option to force usage
 * of MRs to help testing this code path.
	

>  	if (rdma_protocol_iwarp(dev, port_num) && dir == DMA_FROM_DEVICE)
>  		return true;
> +	if (dev->attrs.max_sgl_rd && dir == DMA_FROM_DEVICE &&
> +	    dma_nents > dev->attrs.max_sgl_rd)
> +		return true;

This can be simplified to:

	if (dir == DMA_FROM_DEVICE &&
	    (rdma_protocol_iwarp(dev, port_num) ||
	     (dev->attrs.max_sgl_rd && dma_nents > dev->attrs.max_sgl_rd)))
		return true;
Leon Romanovsky Oct. 7, 2019, 12:36 p.m. UTC | #2 
On Mon, Oct 07, 2019 at 05:12:44AM -0700, Christoph Hellwig wrote:
> Sorry for nitpicking again, but..
>
> On Mon, Oct 07, 2019 at 02:58:18PM +0300, Leon Romanovsky wrote:
> > @@ -37,15 +39,15 @@ static inline bool rdma_rw_can_use_mr(struct ib_device *dev, u8 port_num)
> >   * Check if the device will use memory registration for this RW operation.
> >   * We currently always use memory registrations for iWarp RDMA READs, and
> >   * have a debug option to force usage of MRs.
> > - *
> > - * XXX: In the future we can hopefully fine tune this based on HCA driver
> > - * input.
>
> The above comment needs an updated a la:
>
>  * Check if the device will use memory registration for this RW operation.
>  * For RDMA READs we must use MRs on iWarp and can optionaly use them as an
>  * optimaztion otherwise.  Additionally we have a debug option to force usage
>  * of MRs to help testing this code path.
>
>
> >  	if (rdma_protocol_iwarp(dev, port_num) && dir == DMA_FROM_DEVICE)
> >  		return true;
> > +	if (dev->attrs.max_sgl_rd && dir == DMA_FROM_DEVICE &&
> > +	    dma_nents > dev->attrs.max_sgl_rd)
> > +		return true;
>
> This can be simplified to:
>
> 	if (dir == DMA_FROM_DEVICE &&
> 	    (rdma_protocol_iwarp(dev, port_num) ||
> 	     (dev->attrs.max_sgl_rd && dma_nents > dev->attrs.max_sgl_rd)))
> 		return true;

I don't think that it simplifies and wanted to make separate checks to
be separated. For example, rdma_protocol_iwarp() has nothing to do with
attrs.max_sgl_rd.

I'll fix comment.

Thanks
Christoph Hellwig Oct. 7, 2019, 12:48 p.m. UTC | #3 
On Mon, Oct 07, 2019 at 03:36:56PM +0300, Leon Romanovsky wrote:
> > >  	if (rdma_protocol_iwarp(dev, port_num) && dir == DMA_FROM_DEVICE)
> > >  		return true;
> > > +	if (dev->attrs.max_sgl_rd && dir == DMA_FROM_DEVICE &&
> > > +	    dma_nents > dev->attrs.max_sgl_rd)
> > > +		return true;
> >
> > This can be simplified to:
> >
> > 	if (dir == DMA_FROM_DEVICE &&
> > 	    (rdma_protocol_iwarp(dev, port_num) ||
> > 	     (dev->attrs.max_sgl_rd && dma_nents > dev->attrs.max_sgl_rd)))
> > 		return true;
> 
> I don't think that it simplifies and wanted to make separate checks to
> be separated. For example, rdma_protocol_iwarp() has nothing to do with
> attrs.max_sgl_rd.

The important bit is to have the DMA_FROM_DEVICE check only once, as
we only do the registration for reads with either parameter.  So if
you want it more verbose the wya would be:

 	if (dir == DMA_FROM_DEVICE) {
		if (rdma_protocol_iwarp(dev, port_num))
			return true;
		if (dev->attrs.max_sgl_rd && dma_nents > dev->attrs.max_sgl_rd)
			return true;
	}
Leon Romanovsky Oct. 7, 2019, 1:17 p.m. UTC | #4 
On Mon, Oct 07, 2019 at 05:48:31AM -0700, Christoph Hellwig wrote:
> On Mon, Oct 07, 2019 at 03:36:56PM +0300, Leon Romanovsky wrote:
> > > >  	if (rdma_protocol_iwarp(dev, port_num) && dir == DMA_FROM_DEVICE)
> > > >  		return true;
> > > > +	if (dev->attrs.max_sgl_rd && dir == DMA_FROM_DEVICE &&
> > > > +	    dma_nents > dev->attrs.max_sgl_rd)
> > > > +		return true;
> > >
> > > This can be simplified to:
> > >
> > > 	if (dir == DMA_FROM_DEVICE &&
> > > 	    (rdma_protocol_iwarp(dev, port_num) ||
> > > 	     (dev->attrs.max_sgl_rd && dma_nents > dev->attrs.max_sgl_rd)))
> > > 		return true;
> >
> > I don't think that it simplifies and wanted to make separate checks to
> > be separated. For example, rdma_protocol_iwarp() has nothing to do with
> > attrs.max_sgl_rd.
>
> The important bit is to have the DMA_FROM_DEVICE check only once, as
> we only do the registration for reads with either parameter.  So if
> you want it more verbose the wya would be:
>
>  	if (dir == DMA_FROM_DEVICE) {
> 		if (rdma_protocol_iwarp(dev, port_num))
> 			return true;
> 		if (dev->attrs.max_sgl_rd && dma_nents > dev->attrs.max_sgl_rd)
> 			return true;
> 	}

I'm doing it now, Thank you for taking time to explain.
diff mbox series

Patch

diff --git a/drivers/infiniband/core/rw.c b/drivers/infiniband/core/rw.c
index 5337393d4dfe..8739bd28232b 100644
--- a/drivers/infiniband/core/rw.c
+++ b/drivers/infiniband/core/rw.c
@@ -20,14 +20,16 @@  module_param_named(force_mr, rdma_rw_force_mr, bool, 0);
 MODULE_PARM_DESC(force_mr, "Force usage of MRs for RDMA READ/WRITE operations");

 /*
- * Check if the device might use memory registration.  This is currently only
- * true for iWarp devices. In the future we can hopefully fine tune this based
- * on HCA driver input.
+ * Check if the device might use memory registration. This is currently
+ * true for iWarp devices and devices that have optimized SGL registration
+ * logic.
  */
 static inline bool rdma_rw_can_use_mr(struct ib_device *dev, u8 port_num)
 {
 	if (rdma_protocol_iwarp(dev, port_num))
 		return true;
+	if (dev->attrs.max_sgl_rd)
+		return true;
 	if (unlikely(rdma_rw_force_mr))
 		return true;
 	return false;
@@ -37,15 +39,15 @@  static inline bool rdma_rw_can_use_mr(struct ib_device *dev, u8 port_num)
  * Check if the device will use memory registration for this RW operation.
  * We currently always use memory registrations for iWarp RDMA READs, and
  * have a debug option to force usage of MRs.
- *
- * XXX: In the future we can hopefully fine tune this based on HCA driver
- * input.
  */
 static inline bool rdma_rw_io_needs_mr(struct ib_device *dev, u8 port_num,
 		enum dma_data_direction dir, int dma_nents)
 {
 	if (rdma_protocol_iwarp(dev, port_num) && dir == DMA_FROM_DEVICE)
 		return true;
+	if (dev->attrs.max_sgl_rd && dir == DMA_FROM_DEVICE &&
+	    dma_nents > dev->attrs.max_sgl_rd)
+		return true;
 	if (unlikely(rdma_rw_force_mr))
 		return true;
 	return false;
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 4f671378dbfc..60fd98a9b7e8 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -445,6 +445,8 @@  struct ib_device_attr {
 	struct ib_tm_caps	tm_caps;
 	struct ib_cq_caps       cq_caps;
 	u64			max_dm_size;
+	/* Max entries for sgl for optimized performance per READ */
+	u32			max_sgl_rd;
 };

 enum ib_mtu {