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xprtrdma: Reduce max_frwr_depth 

Some devices advertise a large max_fast_reg_page_list_len
capability, but perform optimally when MRs are significantly smaller
than that depth -- probably when the MR itself is no larger than a
page.

By default, the RDMA R/W core API uses max_sge_rd as the maximum
page depth for MRs. For some devices, the value of max_sge_rd is
1, which is also not optimal. Thus, when max_sge_rd is larger than
1, use that value. Otherwise use the value of the
max_fast_reg_page_list_len attribute.

I've tested this with CX-3 Pro, FastLinq, and CX-5 devices. It
reproducibly improves the throughput of large I/Os by several
percent.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
This commit is contained in:
Chuck Lever 2018-12-19 10:58:51 -05:00 committed by Anna Schumaker
parent 6946f82380
commit a78868497c
1 changed files with 11 additions and 4 deletions
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15
net/sunrpc/xprtrdma/frwr_ops.c
View File

@ -193,10 +193,17 @@ frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
if (attrs->device_cap_flags & IB_DEVICE_SG_GAPS_REG)
ia->ri_mrtype = IB_MR_TYPE_SG_GAPS;
ia->ri_max_frwr_depth =
min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
attrs->max_fast_reg_page_list_len);
dprintk("RPC: %s: device's max FR page list len = %u\n",
/* Quirk: Some devices advertise a large max_fast_reg_page_list_len
* capability, but perform optimally when the MRs are not larger
* than a page.
*/
if (attrs->max_sge_rd > 1)
ia->ri_max_frwr_depth = attrs->max_sge_rd;
else
ia->ri_max_frwr_depth = attrs->max_fast_reg_page_list_len;
if (ia->ri_max_frwr_depth > RPCRDMA_MAX_DATA_SEGS)
ia->ri_max_frwr_depth = RPCRDMA_MAX_DATA_SEGS;
dprintk("RPC: %s: max FR page list depth = %u\n",
__func__, ia->ri_max_frwr_depth);
/* Add room for frwr register and invalidate WRs.