iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

IB/hfi1: Fix a latency issue for small messages

Browse Source 
A recent performance enhancement introduced a latency issue in the
HFI message path.  The new algorithm removed a forced call send for
PIO messages and added a forced schedule event for messages larger
than the MTU.

For PIO, the schedule path can introduce thrashing that can
significantly impact the throughput for small messages.

If a message size is within the PIO threshold, always take the send
path.

Fixes: 0b79b27748cb ("IB/{hfi1, qib, rdmavt}: Schedule multi RC/UC packets instead of posting")
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
This commit is contained in:
Michael J. Ruhl 2018-11-28 06:44:36 -08:00 committed by Doug Ledford
parent 7bca603a69
commit 90b2620e6a
1 changed files with 7 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/infiniband/hw/hfi1/qp.c
View File

@ -340,6 +340,13 @@ int hfi1_setup_wqe(struct rvt_qp *qp, struct rvt_swqe *wqe, bool *call_send)
default:
break;
}
/*
* System latency between send and schedule is large enough that
* forcing call_send to true for piothreshold packets is necessary.
*/
if (wqe->length <= piothreshold)
*call_send = true;
return 0;
}