[ofw] [IPOIB_NDIS6_CM] enhance wc linking loop performance by removing array index calculations

[Tzachi Dar]

Have you been actually being able to measure a difference?

I believe that your code is better, but I wander if it really has an affect that we can measure.

Thanks
Tzachi

> -----Original Message-----
> From: Smith, Stan [mailto:stan.smith at intel.com]
> Sent: Wednesday, August 04, 2010 8:43 PM
> To: Tzachi Dar
> Cc: ofw at lists.openfabrics.org
> Subject: [IPOIB_NDIS6_CM] enhance wc linking loop performance by
> removing array index calculations
> 
> 
> Hello,
> 
> While reading IPOIB code I noticed a minor speed enhancement in CQ
> callback routines.
> When linking WC (work complete) items into a list, by removing the
> array index calculations in favor of pointer arithmetic the loop will
> execute slightly faster.
> 
> Worth a commit?
> 
> stan.
> 
> --- A/ulp/ipoib_NDIS6_CM/kernel/ipoib_endpoint.cpp      Wed Aug 04
> 10:30:43 2010
> +++ B/ulp/ipoib_NDIS6_CM/kernel/ipoib_endpoint.cpp      Wed Aug 04
> 10:28:59 2010
> @@ -888,9 +888,10 @@
>                 p_port->p_adapter->p_ifc->modify_qp( p_endpt-
> >conn.h_send_qp, &mod_attr );
>                 p_port->p_adapter->p_ifc->modify_qp( p_endpt-
> >conn.h_recv_qp, &mod_attr );
> 
> -               for( i = 0; i < MAX_RECV_WC; i++ )
> -                       wc[i].p_next = &wc[i + 1];
> -               wc[MAX_RECV_WC - 1].p_next = NULL;
> +       for( p_free_wc=wc; p_free_wc < &wc[MAX_RECV_WC]; p_free_wc++ )
> +               p_free_wc->p_next = p_free_wc + 1;
> +
> +       (--p_free_wc)->p_next = NULL;
> 
>                 do
>                 {
> 
> --- A/ulp/ipoib_NDIS6_CM/kernel/ipoib_port.cpp  Wed Aug 04 10:29:33
> 2010
> +++ B/ulp/ipoib_NDIS6_CM/kernel/ipoib_port.cpp  Wed Aug 04 10:28:31
> 2010
> @@ -1987,7 +1987,6 @@
>         ib_wc_t                         wc[MAX_RECV_WC], *p_free,
> *p_wc;
>         int32_t                         NBL_cnt, recv_cnt = 0,
> shortage, discarded;
>         cl_qlist_t                      done_list, bad_list;
> -       size_t                          i;
>         ULONG                           recv_complete_flags = 0;
>         BOOLEAN                         res;
> 
> @@ -2017,9 +2016,11 @@
>         cl_qlist_init( &bad_list );
> 
>         ipoib_port_ref( p_port, ref_recv_cb );
> -       for( i = 0; i < MAX_RECV_WC; i++ )
> -               wc[i].p_next = &wc[i + 1];
> -       wc[MAX_RECV_WC - 1].p_next = NULL;
> +
> +       for( p_free=wc; p_free < &wc[MAX_RECV_WC]; p_free++ )
> +               p_free->p_next = p_free + 1;
> +
> +       (--p_free)->p_next = NULL;
> 
>         /*
>          * We'll be accessing the endpoint map so take a reference
> @@ -5769,7 +5770,6 @@
>         cl_qlist_t                      done_list;
>         ipoib_endpt_t           *p_endpt;
>         ip_stat_sel_t           type;
> -       size_t                          i;
>         NET_BUFFER                      *p_netbuffer = NULL;
>         ipoib_send_NB_SG        *s_buf;
> 
> @@ -5798,9 +5798,10 @@
>         //cl_qlist_check_validity(&p_port->send_mgr.pending_list);
>         ipoib_port_ref( p_port, ref_send_cb );
> 
> -       for( i = 0; i < MAX_SEND_WC; i++ )
> -               wc[i].p_next = &wc[i + 1];
> -       wc[MAX_SEND_WC - 1].p_next = NULL;
> +       for( p_free=wc; p_free < &wc[MAX_SEND_WC]; p_free++ )
> +               p_free->p_next = p_free + 1;
> +
> +       (--p_free)->p_next = NULL;
> 
>         do
>         {
>