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Date: Tue, 19 Mar 2019 08:50:22 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
To: Gage Eads <gage.eads@intel.com>
Cc: dev@dpdk.org, olivier.matz@6wind.com, arybchenko@solarflare.com,
bruce.richardson@intel.com, konstantin.ananyev@intel.com,
jerinj@marvell.com, mczekaj@marvell.com, nd@arm.com, Ola.Liljedahl@arm.com
Message-ID: <20190319085022.5a971ac2@shemminger-XPS-13-9360>
In-Reply-To: <20190318213555.17345-4-gage.eads@intel.com>
References: <20190306150342.2894-1-gage.eads@intel.com>
<20190318213555.17345-1-gage.eads@intel.com>
<20190318213555.17345-4-gage.eads@intel.com>
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Subject: Re: [dpdk-dev] [PATCH v7 3/6] ring: add a lock-free implementation
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On Mon, 18 Mar 2019 16:35:52 -0500
Gage Eads <gage.eads@intel.com> wrote:
>
> +/* The actual enqueue of pointers on the lock-free ring, used by the
> + * single-producer lock-free enqueue function.
> + */
> +#define ENQUEUE_PTRS_LF(r, base, prod_head, obj_table, n) do { \
> + unsigned int i; \
> + const uint32_t size = (r)->size; \
> + size_t idx = prod_head & (r)->mask; \
> + size_t new_cnt = prod_head + size; \
> + struct rte_ring_lf_entry *ring = (struct rte_ring_lf_entry *)base; \
> + unsigned int mask = ~0x3; \
> + if (likely(idx + n < size)) { \
> + for (i = 0; i < (n & mask); i += 4, idx += 4) { \
> + ring[idx].ptr = obj_table[i]; \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx + 1].ptr = obj_table[i + 1]; \
> + ring[idx + 1].cnt = (new_cnt + i + 1) >> r->log2_size; \
> + ring[idx + 2].ptr = obj_table[i + 2]; \
> + ring[idx + 2].cnt = (new_cnt + i + 2) >> r->log2_size; \
> + ring[idx + 3].ptr = obj_table[i + 3]; \
> + ring[idx + 3].cnt = (new_cnt + i + 3) >> r->log2_size; \
> + } \
> + switch (n & 0x3) { \
> + case 3: \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx++].ptr = obj_table[i++]; /* fallthrough */ \
> + case 2: \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx++].ptr = obj_table[i++]; /* fallthrough */ \
> + case 1: \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx++].ptr = obj_table[i++]; \
> + } \
> + } else { \
> + for (i = 0; idx < size; i++, idx++) { \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx].ptr = obj_table[i]; \
> + } \
> + for (idx = 0; i < n; i++, idx++) { \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx].ptr = obj_table[i]; \
> + } \
> + } \
> +} while (0)
> +
> /* the actual copy of pointers on the ring to obj_table.
> * Placed here since identical code needed in both
> * single and multi consumer dequeue functions */
> @@ -314,6 +384,43 @@ void rte_ring_dump(FILE *f, const struct rte_ring *r);
> } \
> } while (0)
>
> +/* The actual copy of pointers on the lock-free ring to obj_table. */
> +#define DEQUEUE_PTRS_LF(r, base, cons_head, obj_table, n) do { \
> + unsigned int i; \
> + size_t idx = cons_head & (r)->mask; \
> + const uint32_t size = (r)->size; \
> + struct rte_ring_lf_entry *ring = (struct rte_ring_lf_entry *)base; \
> + unsigned int mask = ~0x3; \
> + if (likely(idx + n < size)) { \
> + for (i = 0; i < (n & mask); i += 4, idx += 4) {\
> + obj_table[i] = ring[idx].ptr; \
> + obj_table[i + 1] = ring[idx + 1].ptr; \
> + obj_table[i + 2] = ring[idx + 2].ptr; \
> + obj_table[i + 3] = ring[idx + 3].ptr; \
> + } \
> + switch (n & 0x3) { \
> + case 3: \
> + obj_table[i++] = ring[idx++].ptr; /* fallthrough */ \
> + case 2: \
> + obj_table[i++] = ring[idx++].ptr; /* fallthrough */ \
> + case 1: \
> + obj_table[i++] = ring[idx++].ptr; \
> + } \
> + } else { \
> + for (i = 0; idx < size; i++, idx++) \
> + obj_table[i] = ring[idx].ptr; \
> + for (idx = 0; i < n; i++, idx++) \
> + obj_table[i] = ring[idx].ptr; \
> + } \
> +} while (0)
> +
Generic programming like this in C is hard to maintain. Please don't
use large macros. It is better to have two copies than a single large macro.
Better yet use a single inline function than can be expanded in different ways
based on the pointer size.
From mboxrd@z Thu Jan 1 00:00:00 1970
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Date: Tue, 19 Mar 2019 08:50:22 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
To: Gage Eads <gage.eads@intel.com>
Cc: dev@dpdk.org, olivier.matz@6wind.com, arybchenko@solarflare.com,
bruce.richardson@intel.com, konstantin.ananyev@intel.com,
jerinj@marvell.com, mczekaj@marvell.com, nd@arm.com, Ola.Liljedahl@arm.com
Message-ID: <20190319085022.5a971ac2@shemminger-XPS-13-9360>
In-Reply-To: <20190318213555.17345-4-gage.eads@intel.com>
References: <20190306150342.2894-1-gage.eads@intel.com>
<20190318213555.17345-1-gage.eads@intel.com>
<20190318213555.17345-4-gage.eads@intel.com>
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Subject: Re: [dpdk-dev] [PATCH v7 3/6] ring: add a lock-free implementation
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Message-ID: <20190319155022._-IOeaKgQeKuvHagZ161SlLk36sgc71-lj_bbPJFljE@z>
On Mon, 18 Mar 2019 16:35:52 -0500
Gage Eads <gage.eads@intel.com> wrote:
>
> +/* The actual enqueue of pointers on the lock-free ring, used by the
> + * single-producer lock-free enqueue function.
> + */
> +#define ENQUEUE_PTRS_LF(r, base, prod_head, obj_table, n) do { \
> + unsigned int i; \
> + const uint32_t size = (r)->size; \
> + size_t idx = prod_head & (r)->mask; \
> + size_t new_cnt = prod_head + size; \
> + struct rte_ring_lf_entry *ring = (struct rte_ring_lf_entry *)base; \
> + unsigned int mask = ~0x3; \
> + if (likely(idx + n < size)) { \
> + for (i = 0; i < (n & mask); i += 4, idx += 4) { \
> + ring[idx].ptr = obj_table[i]; \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx + 1].ptr = obj_table[i + 1]; \
> + ring[idx + 1].cnt = (new_cnt + i + 1) >> r->log2_size; \
> + ring[idx + 2].ptr = obj_table[i + 2]; \
> + ring[idx + 2].cnt = (new_cnt + i + 2) >> r->log2_size; \
> + ring[idx + 3].ptr = obj_table[i + 3]; \
> + ring[idx + 3].cnt = (new_cnt + i + 3) >> r->log2_size; \
> + } \
> + switch (n & 0x3) { \
> + case 3: \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx++].ptr = obj_table[i++]; /* fallthrough */ \
> + case 2: \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx++].ptr = obj_table[i++]; /* fallthrough */ \
> + case 1: \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx++].ptr = obj_table[i++]; \
> + } \
> + } else { \
> + for (i = 0; idx < size; i++, idx++) { \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx].ptr = obj_table[i]; \
> + } \
> + for (idx = 0; i < n; i++, idx++) { \
> + ring[idx].cnt = (new_cnt + i) >> r->log2_size; \
> + ring[idx].ptr = obj_table[i]; \
> + } \
> + } \
> +} while (0)
> +
> /* the actual copy of pointers on the ring to obj_table.
> * Placed here since identical code needed in both
> * single and multi consumer dequeue functions */
> @@ -314,6 +384,43 @@ void rte_ring_dump(FILE *f, const struct rte_ring *r);
> } \
> } while (0)
>
> +/* The actual copy of pointers on the lock-free ring to obj_table. */
> +#define DEQUEUE_PTRS_LF(r, base, cons_head, obj_table, n) do { \
> + unsigned int i; \
> + size_t idx = cons_head & (r)->mask; \
> + const uint32_t size = (r)->size; \
> + struct rte_ring_lf_entry *ring = (struct rte_ring_lf_entry *)base; \
> + unsigned int mask = ~0x3; \
> + if (likely(idx + n < size)) { \
> + for (i = 0; i < (n & mask); i += 4, idx += 4) {\
> + obj_table[i] = ring[idx].ptr; \
> + obj_table[i + 1] = ring[idx + 1].ptr; \
> + obj_table[i + 2] = ring[idx + 2].ptr; \
> + obj_table[i + 3] = ring[idx + 3].ptr; \
> + } \
> + switch (n & 0x3) { \
> + case 3: \
> + obj_table[i++] = ring[idx++].ptr; /* fallthrough */ \
> + case 2: \
> + obj_table[i++] = ring[idx++].ptr; /* fallthrough */ \
> + case 1: \
> + obj_table[i++] = ring[idx++].ptr; \
> + } \
> + } else { \
> + for (i = 0; idx < size; i++, idx++) \
> + obj_table[i] = ring[idx].ptr; \
> + for (idx = 0; i < n; i++, idx++) \
> + obj_table[i] = ring[idx].ptr; \
> + } \
> +} while (0)
> +
Generic programming like this in C is hard to maintain. Please don't
use large macros. It is better to have two copies than a single large macro.
Better yet use a single inline function than can be expanded in different ways
based on the pointer size.