On Wednesday 09 January 2008 23:53, Roland Dreier wrote:
> Isn't that just a crazy way of coming up with a new name for unsigned long?
>
> How about something like this (it seems to generate pretty good code
> on x86-64 at least):
>
> diff --git a/src/qp.c b/src/qp.c
> index 8b4adaa..5721860 100644
> --- a/src/qp.c
> +++ b/src/qp.c
> @@ -168,6 +168,20 @@ static void set_data_seg(struct mlx4_wqe_data_seg *dseg,
> struct ibv_sge *sg)
> dseg->byte_count = htonl(sg->length);
> }
>
> +/*
> + * Avoid using memcpy() to copy to BlueFlame page, since memcpy()
> + * implementations may use move-string-buffer assembler instructions,
> + * which do not guarantee order of copying.
> + */
> +static void mlx4_bf_copy(unsigned long *dst, unsigned long *src, unsigned
> bytecnt)
> +{
> + while (bytecnt > 0) {
> + *dst++ = *src++;
> + *dst++ = *src++;
> + bytecnt -= 2 * sizeof (long);
> + }
> +}
> +
Agreed regarding the unsigned long. However, your solution still results in a
procedure call
(mlx4_bf_copy is compiled as a procedure using gcc 4.1.0 on an X86_64 host,
even if I add "inline").
I would prefer the patch below (which does generate inline code, and does the
(sizeof(unsigned long) * 2) calculation just once).
- Jack
=======================
diff --git a/src/qp.c b/src/qp.c
index bced740..8fc8450 100644
--- a/src/qp.c
+++ b/src/qp.c
@@ -391,7 +391,24 @@ out:
pthread_spin_lock(&ctx->bf_lock);
- memcpy(ctx->bf_page + ctx->bf_offset, ctrl, align(size * 16,
64));
+ /*
+ * Avoid using memcpy to copy to BlueFlame page, since recent
+ * memcpy implementations use move-string-buffer assembler
+ * instructions, which do not guarantee order of copying.
+ */
+
+ {
+ unsigned long *target =
+ (unsigned long *) (ctx->bf_page +
ctx->bf_offset);
+ unsigned long *src = (unsigned long *) ctrl;
+ int n = align(size * 16, 64) / (sizeof(unsigned long) *
2);
+ while (n > 0) {
+ *target++ = *src++;
+ *target++ = *src++;
+ --n;
+ }
+ }
+
wc_wmb();
ctx->bf_offset ^= ctx->bf_buf_size;
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