From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH 1/5] vhost: refactor rte_vhost_dequeue_burst
Date: Wed, 2 Dec 2015 23:02:44 -0800
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References: <1449122773-25510-1-git-send-email-yuanhan.liu@linux.intel.com>
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Cc: dev@dpdk.org, Victor Kaplansky <vkaplans@redhat.com>,
 "Michael S. Tsirkin" <mst@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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On Thu,  3 Dec 2015 14:06:09 +0800
Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote:

> +#define COPY(dst, src) do {						\
> +	cpy_len = RTE_MIN(desc_avail, mbuf_avail);			\
> +	rte_memcpy((void *)(uintptr_t)(dst),				\
> +		   (const void *)(uintptr_t)(src), cpy_len);		\
> +									\
> +	mbuf_avail  -= cpy_len;						\
> +	mbuf_offset += cpy_len;						\
> +	desc_avail  -= cpy_len;						\
> +	desc_offset += cpy_len;						\
> +} while(0)
> +

I see lots of issues here.

All those void * casts are unnecessary, C casts arguements already.
rte_memcpy is slower for constant size values than memcpy()

This macro violates the rule that ther should be no hidden variables
in a macro. I.e you are assuming cpy_len, desc_avail, and mbuf_avail
are defined in all code using the macro.

Why use an un-typed macro when an inline function would be just
as fast and give type safety?