RE: [PATCH 2/2] iw_cxgb4: add fast-path for small REG_MR operations

On Fri, Sep 16, 2016 at 07:54:52AM -0700, Steve Wise wrote:

quoted

When processing a REG_MR work request, if fw supports the
FW_RI_NSMR_TPTE_WR work request, and if the page list for this
registration is <= 2 pages, and the current state of the mr is INVALID,
then use FW_RI_NSMR_TPTE_WR to pass down a fully populated TPTE for

FW

quoted

to write.  This avoids FW having to do an async read of the TPTE

blocking

quoted

the SQ until the read completes.

To know if the current MR state is INVALID or not, iw_cxgb4 must track

the

quoted

state of each fastreg MR.  The c4iw_mr struct state is updated as REG_MR
and LOCAL_INV WRs are posted and completed, when a reg_mr is

destroyed,

quoted

and when RECV completions are processed that include a local

invalidation.

quoted

This optimization increases small IO IOPS for both iSER and NVMF.

Signed-off-by: Steve Wise <redacted>
---

<...>

quoted

+			      struct ib_reg_wr *wr, struct c4iw_mr *mhp,
+			      u8 *len16)
+{
+	__be64 *p = (__be64 *)fr->pbl;
+
+	fr->r2 = cpu_to_be32(0);

Is there any difference between the line above and "fr->r2 = 0"?

It makes sparse happy, IIRC...



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On Sun, Sep 18, 2016 at 07:40:29PM -0500, Steve Wise wrote:

quoted

On Fri, Sep 16, 2016 at 07:54:52AM -0700, Steve Wise wrote:

quoted

When processing a REG_MR work request, if fw supports the
FW_RI_NSMR_TPTE_WR work request, and if the page list for this
registration is <= 2 pages, and the current state of the mr is INVALID,
then use FW_RI_NSMR_TPTE_WR to pass down a fully populated TPTE for

FW

quoted

to write.  This avoids FW having to do an async read of the TPTE

blocking

quoted

quoted

the SQ until the read completes.

To know if the current MR state is INVALID or not, iw_cxgb4 must track

the

quoted

quoted

state of each fastreg MR.  The c4iw_mr struct state is updated as REG_MR
and LOCAL_INV WRs are posted and completed, when a reg_mr is

destroyed,

quoted

and when RECV completions are processed that include a local

invalidation.

quoted

quoted

This optimization increases small IO IOPS for both iSER and NVMF.

Signed-off-by: Steve Wise <redacted>
---

<...>

quoted

+			      struct ib_reg_wr *wr, struct c4iw_mr *mhp,
+			      u8 *len16)
+{
+	__be64 *p = (__be64 *)fr->pbl;
+
+	fr->r2 = cpu_to_be32(0);

Is there any difference between the line above and "fr->r2 = 0"?

It makes sparse happy, IIRC...

Strange, but ok :)